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Message-ID: <20090821184602.GA428@linux.vnet.ibm.com>
Date: Fri, 21 Aug 2009 11:46:02 -0700
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: linux-kernel@...r.kernel.org
Cc: schwidefsky@...ibm.com, mingo@...e.hu, tglx@...utronix.de,
gerald.schaefer@...ibm.com, manfred@...orfullife.com, ihno@...e.de,
gregkh@...e.de, pavel@....cz
Subject: [PATCH 2.6.27] Backport TREE_RCU to 2.6.27
This is a backport of TREE_RCU to 2.6.27. Testing is in progress,
with encouraging results thus far (famous last words). Given that I
developed TREE_RCU on 2.6.26 and 2.6.27, I am hopeful that things will
progress nicely (more famous last words). ;-)
This is a single patch combining a number of mainline patches for
testing convenience. I have them applied to my local git tree as
a series of cherry-picks of the corresponding mainline commits with
a couple of additional merge-conflict commits as follows:
726befc8122a259af7132f5accf48c01e719bee1 rcu: Add __rcu_pending tracing to hierarchical RCU
7fb69d35deadcf3a133c5b2d93ff3602beb7f6f5 rcu: Make hierarchical RCU less IPI-happy
b007daec94213e8012f4b7608e78e1ccdd4b3e3c rcu: Teach RCU that idle task is not quiscent state at boot (fix merge conflict)
0def84e22f98c09deca952c004845838800ede83 rcu: Teach RCU that idle task is not quiscent state at boot (merge conflict)
569dc44edc63d7c1d876b98af274d779e2bc8616 rcu: add __cpuinit to rcu_init_percpu_data()
a714405953163fc3d69fb9955c378933f7f28fac rcu: make treercu safe for suspend and resume
3724df4eaa756542233685c93923f2933eda3481 rcu: fix rcutree grace-period-latency bug on small systems
8f7b6bc3b347a18bb29d8edd7a2a3eb22f954a4e "Tree RCU": scalable classic RCU implementation (merge-conflict fix)
b802a3fe204973b727aa7e0e3ae731a2c7830e2b "Tree RCU": scalable classic RCU implementation (merge conflict)
If this is useful, I would of course be happy to create a patch set,
bisectable or otherwise (of course, the above series is -not- bisectable).
Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
Documentation/RCU/00-INDEX | 2
Documentation/RCU/trace.txt | 413 ++++++++
arch/powerpc/platforms/pseries/rtasd.c | 4
include/linux/hardirq.h | 14
include/linux/rcuclassic.h | 6
include/linux/rcupdate.h | 16
include/linux/rcupreempt.h | 15
include/linux/rcutree.h | 341 +++++++
init/Kconfig | 18
init/main.c | 3
kernel/Kconfig.preempt | 62 +
kernel/Makefile | 6
kernel/rcuclassic.c | 6
kernel/rcupdate.c | 8
kernel/rcupreempt.c | 26
kernel/rcupreempt_trace.c | 10
kernel/rcutree.c | 1534 +++++++++++++++++++++++++++++++++
kernel/rcutree_trace.c | 329 +++++++
kernel/softirq.c | 5
lib/Kconfig.debug | 13
20 files changed, 2796 insertions(+), 35 deletions(-)
diff --git a/Documentation/RCU/00-INDEX b/Documentation/RCU/00-INDEX
index 461481d..7dc0695 100644
--- a/Documentation/RCU/00-INDEX
+++ b/Documentation/RCU/00-INDEX
@@ -16,6 +16,8 @@ RTFP.txt
- List of RCU papers (bibliography) going back to 1980.
torture.txt
- RCU Torture Test Operation (CONFIG_RCU_TORTURE_TEST)
+trace.txt
+ - CONFIG_RCU_TRACE debugfs files and formats
UP.txt
- RCU on Uniprocessor Systems
whatisRCU.txt
diff --git a/Documentation/RCU/trace.txt b/Documentation/RCU/trace.txt
new file mode 100644
index 0000000..0688482
--- /dev/null
+++ b/Documentation/RCU/trace.txt
@@ -0,0 +1,413 @@
+CONFIG_RCU_TRACE debugfs Files and Formats
+
+
+The rcupreempt and rcutree implementations of RCU provide debugfs trace
+output that summarizes counters and state. This information is useful for
+debugging RCU itself, and can sometimes also help to debug abuses of RCU.
+Note that the rcuclassic implementation of RCU does not provide debugfs
+trace output.
+
+The following sections describe the debugfs files and formats for
+preemptable RCU (rcupreempt) and hierarchical RCU (rcutree).
+
+
+Preemptable RCU debugfs Files and Formats
+
+This implementation of RCU provides three debugfs files under the
+top-level directory RCU: rcu/rcuctrs (which displays the per-CPU
+counters used by preemptable RCU) rcu/rcugp (which displays grace-period
+counters), and rcu/rcustats (which internal counters for debugging RCU).
+
+The output of "cat rcu/rcuctrs" looks as follows:
+
+CPU last cur F M
+ 0 5 -5 0 0
+ 1 -1 0 0 0
+ 2 0 1 0 0
+ 3 0 1 0 0
+ 4 0 1 0 0
+ 5 0 1 0 0
+ 6 0 2 0 0
+ 7 0 -1 0 0
+ 8 0 1 0 0
+ggp = 26226, state = waitzero
+
+The per-CPU fields are as follows:
+
+o "CPU" gives the CPU number. Offline CPUs are not displayed.
+
+o "last" gives the value of the counter that is being decremented
+ for the current grace period phase. In the example above,
+ the counters sum to 4, indicating that there are still four
+ RCU read-side critical sections still running that started
+ before the last counter flip.
+
+o "cur" gives the value of the counter that is currently being
+ both incremented (by rcu_read_lock()) and decremented (by
+ rcu_read_unlock()). In the example above, the counters sum to
+ 1, indicating that there is only one RCU read-side critical section
+ still running that started after the last counter flip.
+
+o "F" indicates whether RCU is waiting for this CPU to acknowledge
+ a counter flip. In the above example, RCU is not waiting on any,
+ which is consistent with the state being "waitzero" rather than
+ "waitack".
+
+o "M" indicates whether RCU is waiting for this CPU to execute a
+ memory barrier. In the above example, RCU is not waiting on any,
+ which is consistent with the state being "waitzero" rather than
+ "waitmb".
+
+o "ggp" is the global grace-period counter.
+
+o "state" is the RCU state, which can be one of the following:
+
+ o "idle": there is no grace period in progress.
+
+ o "waitack": RCU just incremented the global grace-period
+ counter, which has the effect of reversing the roles of
+ the "last" and "cur" counters above, and is waiting for
+ all the CPUs to acknowledge the flip. Once the flip has
+ been acknowledged, CPUs will no longer be incrementing
+ what are now the "last" counters, so that their sum will
+ decrease monotonically down to zero.
+
+ o "waitzero": RCU is waiting for the sum of the "last" counters
+ to decrease to zero.
+
+ o "waitmb": RCU is waiting for each CPU to execute a memory
+ barrier, which ensures that instructions from a given CPU's
+ last RCU read-side critical section cannot be reordered
+ with instructions following the memory-barrier instruction.
+
+The output of "cat rcu/rcugp" looks as follows:
+
+oldggp=48870 newggp=48873
+
+Note that reading from this file provokes a synchronize_rcu(). The
+"oldggp" value is that of "ggp" from rcu/rcuctrs above, taken before
+executing the synchronize_rcu(), and the "newggp" value is also the
+"ggp" value, but taken after the synchronize_rcu() command returns.
+
+
+The output of "cat rcu/rcugp" looks as follows:
+
+na=1337955 nl=40 wa=1337915 wl=44 da=1337871 dl=0 dr=1337871 di=1337871
+1=50989 e1=6138 i1=49722 ie1=82 g1=49640 a1=315203 ae1=265563 a2=49640
+z1=1401244 ze1=1351605 z2=49639 m1=5661253 me1=5611614 m2=49639
+
+These are counters tracking internal preemptable-RCU events, however,
+some of them may be useful for debugging algorithms using RCU. In
+particular, the "nl", "wl", and "dl" values track the number of RCU
+callbacks in various states. The fields are as follows:
+
+o "na" is the total number of RCU callbacks that have been enqueued
+ since boot.
+
+o "nl" is the number of RCU callbacks waiting for the previous
+ grace period to end so that they can start waiting on the next
+ grace period.
+
+o "wa" is the total number of RCU callbacks that have started waiting
+ for a grace period since boot. "na" should be roughly equal to
+ "nl" plus "wa".
+
+o "wl" is the number of RCU callbacks currently waiting for their
+ grace period to end.
+
+o "da" is the total number of RCU callbacks whose grace periods
+ have completed since boot. "wa" should be roughly equal to
+ "wl" plus "da".
+
+o "dr" is the total number of RCU callbacks that have been removed
+ from the list of callbacks ready to invoke. "dr" should be roughly
+ equal to "da".
+
+o "di" is the total number of RCU callbacks that have been invoked
+ since boot. "di" should be roughly equal to "da", though some
+ early versions of preemptable RCU had a bug so that only the
+ last CPU's count of invocations was displayed, rather than the
+ sum of all CPU's counts.
+
+o "1" is the number of calls to rcu_try_flip(). This should be
+ roughly equal to the sum of "e1", "i1", "a1", "z1", and "m1"
+ described below. In other words, the number of times that
+ the state machine is visited should be equal to the sum of the
+ number of times that each state is visited plus the number of
+ times that the state-machine lock acquisition failed.
+
+o "e1" is the number of times that rcu_try_flip() was unable to
+ acquire the fliplock.
+
+o "i1" is the number of calls to rcu_try_flip_idle().
+
+o "ie1" is the number of times rcu_try_flip_idle() exited early
+ due to the calling CPU having no work for RCU.
+
+o "g1" is the number of times that rcu_try_flip_idle() decided
+ to start a new grace period. "i1" should be roughly equal to
+ "ie1" plus "g1".
+
+o "a1" is the number of calls to rcu_try_flip_waitack().
+
+o "ae1" is the number of times that rcu_try_flip_waitack() found
+ that at least one CPU had not yet acknowledge the new grace period
+ (AKA "counter flip").
+
+o "a2" is the number of time rcu_try_flip_waitack() found that
+ all CPUs had acknowledged. "a1" should be roughly equal to
+ "ae1" plus "a2". (This particular output was collected on
+ a 128-CPU machine, hence the smaller-than-usual fraction of
+ calls to rcu_try_flip_waitack() finding all CPUs having already
+ acknowledged.)
+
+o "z1" is the number of calls to rcu_try_flip_waitzero().
+
+o "ze1" is the number of times that rcu_try_flip_waitzero() found
+ that not all of the old RCU read-side critical sections had
+ completed.
+
+o "z2" is the number of times that rcu_try_flip_waitzero() finds
+ the sum of the counters equal to zero, in other words, that
+ all of the old RCU read-side critical sections had completed.
+ The value of "z1" should be roughly equal to "ze1" plus
+ "z2".
+
+o "m1" is the number of calls to rcu_try_flip_waitmb().
+
+o "me1" is the number of times that rcu_try_flip_waitmb() finds
+ that at least one CPU has not yet executed a memory barrier.
+
+o "m2" is the number of times that rcu_try_flip_waitmb() finds that
+ all CPUs have executed a memory barrier.
+
+
+Hierarchical RCU debugfs Files and Formats
+
+This implementation of RCU provides three debugfs files under the
+top-level directory RCU: rcu/rcudata (which displays fields in struct
+rcu_data), rcu/rcugp (which displays grace-period counters), and
+rcu/rcuhier (which displays the struct rcu_node hierarchy).
+
+The output of "cat rcu/rcudata" looks as follows:
+
+rcu:
+ 0 c=4011 g=4012 pq=1 pqc=4011 qp=0 rpfq=1 rp=3c2a dt=23301/73 dn=2 df=1882 of=0 ri=2126 ql=2 b=10
+ 1 c=4011 g=4012 pq=1 pqc=4011 qp=0 rpfq=3 rp=39a6 dt=78073/1 dn=2 df=1402 of=0 ri=1875 ql=46 b=10
+ 2 c=4010 g=4010 pq=1 pqc=4010 qp=0 rpfq=-5 rp=1d12 dt=16646/0 dn=2 df=3140 of=0 ri=2080 ql=0 b=10
+ 3 c=4012 g=4013 pq=1 pqc=4012 qp=1 rpfq=3 rp=2b50 dt=21159/1 dn=2 df=2230 of=0 ri=1923 ql=72 b=10
+ 4 c=4012 g=4013 pq=1 pqc=4012 qp=1 rpfq=3 rp=1644 dt=5783/1 dn=2 df=3348 of=0 ri=2805 ql=7 b=10
+ 5 c=4012 g=4013 pq=0 pqc=4011 qp=1 rpfq=3 rp=1aac dt=5879/1 dn=2 df=3140 of=0 ri=2066 ql=10 b=10
+ 6 c=4012 g=4013 pq=1 pqc=4012 qp=1 rpfq=3 rp=ed8 dt=5847/1 dn=2 df=3797 of=0 ri=1266 ql=10 b=10
+ 7 c=4012 g=4013 pq=1 pqc=4012 qp=1 rpfq=3 rp=1fa2 dt=6199/1 dn=2 df=2795 of=0 ri=2162 ql=28 b=10
+rcu_bh:
+ 0 c=-268 g=-268 pq=1 pqc=-268 qp=0 rpfq=-145 rp=21d6 dt=23301/73 dn=2 df=0 of=0 ri=0 ql=0 b=10
+ 1 c=-268 g=-268 pq=1 pqc=-268 qp=1 rpfq=-170 rp=20ce dt=78073/1 dn=2 df=26 of=0 ri=5 ql=0 b=10
+ 2 c=-268 g=-268 pq=1 pqc=-268 qp=1 rpfq=-83 rp=fbd dt=16646/0 dn=2 df=28 of=0 ri=4 ql=0 b=10
+ 3 c=-268 g=-268 pq=1 pqc=-268 qp=0 rpfq=-105 rp=178c dt=21159/1 dn=2 df=28 of=0 ri=2 ql=0 b=10
+ 4 c=-268 g=-268 pq=1 pqc=-268 qp=1 rpfq=-30 rp=b54 dt=5783/1 dn=2 df=32 of=0 ri=0 ql=0 b=10
+ 5 c=-268 g=-268 pq=1 pqc=-268 qp=1 rpfq=-29 rp=df5 dt=5879/1 dn=2 df=30 of=0 ri=3 ql=0 b=10
+ 6 c=-268 g=-268 pq=1 pqc=-268 qp=1 rpfq=-28 rp=788 dt=5847/1 dn=2 df=32 of=0 ri=0 ql=0 b=10
+ 7 c=-268 g=-268 pq=1 pqc=-268 qp=1 rpfq=-53 rp=1098 dt=6199/1 dn=2 df=30 of=0 ri=3 ql=0 b=10
+
+The first section lists the rcu_data structures for rcu, the second for
+rcu_bh. Each section has one line per CPU, or eight for this 8-CPU system.
+The fields are as follows:
+
+o The number at the beginning of each line is the CPU number.
+ CPUs numbers followed by an exclamation mark are offline,
+ but have been online at least once since boot. There will be
+ no output for CPUs that have never been online, which can be
+ a good thing in the surprisingly common case where NR_CPUS is
+ substantially larger than the number of actual CPUs.
+
+o "c" is the count of grace periods that this CPU believes have
+ completed. CPUs in dynticks idle mode may lag quite a ways
+ behind, for example, CPU 4 under "rcu" above, which has slept
+ through the past 25 RCU grace periods. It is not unusual to
+ see CPUs lagging by thousands of grace periods.
+
+o "g" is the count of grace periods that this CPU believes have
+ started. Again, CPUs in dynticks idle mode may lag behind.
+ If the "c" and "g" values are equal, this CPU has already
+ reported a quiescent state for the last RCU grace period that
+ it is aware of, otherwise, the CPU believes that it owes RCU a
+ quiescent state.
+
+o "pq" indicates that this CPU has passed through a quiescent state
+ for the current grace period. It is possible for "pq" to be
+ "1" and "c" different than "g", which indicates that although
+ the CPU has passed through a quiescent state, either (1) this
+ CPU has not yet reported that fact, (2) some other CPU has not
+ yet reported for this grace period, or (3) both.
+
+o "pqc" indicates which grace period the last-observed quiescent
+ state for this CPU corresponds to. This is important for handling
+ the race between CPU 0 reporting an extended dynticks-idle
+ quiescent state for CPU 1 and CPU 1 suddenly waking up and
+ reporting its own quiescent state. If CPU 1 was the last CPU
+ for the current grace period, then the CPU that loses this race
+ will attempt to incorrectly mark CPU 1 as having checked in for
+ the next grace period!
+
+o "qp" indicates that RCU still expects a quiescent state from
+ this CPU.
+
+o "rpfq" is the number of rcu_pending() calls on this CPU required
+ to induce this CPU to invoke force_quiescent_state().
+
+o "rp" is low-order four hex digits of the count of how many times
+ rcu_pending() has been invoked on this CPU.
+
+o "dt" is the current value of the dyntick counter that is incremented
+ when entering or leaving dynticks idle state, either by the
+ scheduler or by irq. The number after the "/" is the interrupt
+ nesting depth when in dyntick-idle state, or one greater than
+ the interrupt-nesting depth otherwise.
+
+ This field is displayed only for CONFIG_NO_HZ kernels.
+
+o "dn" is the current value of the dyntick counter that is incremented
+ when entering or leaving dynticks idle state via NMI. If both
+ the "dt" and "dn" values are even, then this CPU is in dynticks
+ idle mode and may be ignored by RCU. If either of these two
+ counters is odd, then RCU must be alert to the possibility of
+ an RCU read-side critical section running on this CPU.
+
+ This field is displayed only for CONFIG_NO_HZ kernels.
+
+o "df" is the number of times that some other CPU has forced a
+ quiescent state on behalf of this CPU due to this CPU being in
+ dynticks-idle state.
+
+ This field is displayed only for CONFIG_NO_HZ kernels.
+
+o "of" is the number of times that some other CPU has forced a
+ quiescent state on behalf of this CPU due to this CPU being
+ offline. In a perfect world, this might neve happen, but it
+ turns out that offlining and onlining a CPU can take several grace
+ periods, and so there is likely to be an extended period of time
+ when RCU believes that the CPU is online when it really is not.
+ Please note that erring in the other direction (RCU believing a
+ CPU is offline when it is really alive and kicking) is a fatal
+ error, so it makes sense to err conservatively.
+
+o "ri" is the number of times that RCU has seen fit to send a
+ reschedule IPI to this CPU in order to get it to report a
+ quiescent state.
+
+o "ql" is the number of RCU callbacks currently residing on
+ this CPU. This is the total number of callbacks, regardless
+ of what state they are in (new, waiting for grace period to
+ start, waiting for grace period to end, ready to invoke).
+
+o "b" is the batch limit for this CPU. If more than this number
+ of RCU callbacks is ready to invoke, then the remainder will
+ be deferred.
+
+
+The output of "cat rcu/rcugp" looks as follows:
+
+rcu: completed=33062 gpnum=33063
+rcu_bh: completed=464 gpnum=464
+
+Again, this output is for both "rcu" and "rcu_bh". The fields are
+taken from the rcu_state structure, and are as follows:
+
+o "completed" is the number of grace periods that have completed.
+ It is comparable to the "c" field from rcu/rcudata in that a
+ CPU whose "c" field matches the value of "completed" is aware
+ that the corresponding RCU grace period has completed.
+
+o "gpnum" is the number of grace periods that have started. It is
+ comparable to the "g" field from rcu/rcudata in that a CPU
+ whose "g" field matches the value of "gpnum" is aware that the
+ corresponding RCU grace period has started.
+
+ If these two fields are equal (as they are for "rcu_bh" above),
+ then there is no grace period in progress, in other words, RCU
+ is idle. On the other hand, if the two fields differ (as they
+ do for "rcu" above), then an RCU grace period is in progress.
+
+
+The output of "cat rcu/rcuhier" looks as follows, with very long lines:
+
+c=6902 g=6903 s=2 jfq=3 j=72c7 nfqs=13142/nfqsng=0(13142) fqlh=6
+1/1 0:127 ^0
+3/3 0:35 ^0 0/0 36:71 ^1 0/0 72:107 ^2 0/0 108:127 ^3
+3/3f 0:5 ^0 2/3 6:11 ^1 0/0 12:17 ^2 0/0 18:23 ^3 0/0 24:29 ^4 0/0 30:35 ^5 0/0 36:41 ^0 0/0 42:47 ^1 0/0 48:53 ^2 0/0 54:59 ^3 0/0 60:65 ^4 0/0 66:71 ^5 0/0 72:77 ^0 0/0 78:83 ^1 0/0 84:89 ^2 0/0 90:95 ^3 0/0 96:101 ^4 0/0 102:107 ^5 0/0 108:113 ^0 0/0 114:119 ^1 0/0 120:125 ^2 0/0 126:127 ^3
+rcu_bh:
+c=-226 g=-226 s=1 jfq=-5701 j=72c7 nfqs=88/nfqsng=0(88) fqlh=0
+0/1 0:127 ^0
+0/3 0:35 ^0 0/0 36:71 ^1 0/0 72:107 ^2 0/0 108:127 ^3
+0/3f 0:5 ^0 0/3 6:11 ^1 0/0 12:17 ^2 0/0 18:23 ^3 0/0 24:29 ^4 0/0 30:35 ^5 0/0 36:41 ^0 0/0 42:47 ^1 0/0 48:53 ^2 0/0 54:59 ^3 0/0 60:65 ^4 0/0 66:71 ^5 0/0 72:77 ^0 0/0 78:83 ^1 0/0 84:89 ^2 0/0 90:95 ^3 0/0 96:101 ^4 0/0 102:107 ^5 0/0 108:113 ^0 0/0 114:119 ^1 0/0 120:125 ^2 0/0 126:127 ^3
+
+This is once again split into "rcu" and "rcu_bh" portions. The fields are
+as follows:
+
+o "c" is exactly the same as "completed" under rcu/rcugp.
+
+o "g" is exactly the same as "gpnum" under rcu/rcugp.
+
+o "s" is the "signaled" state that drives force_quiescent_state()'s
+ state machine.
+
+o "jfq" is the number of jiffies remaining for this grace period
+ before force_quiescent_state() is invoked to help push things
+ along. Note that CPUs in dyntick-idle mode thoughout the grace
+ period will not report on their own, but rather must be check by
+ some other CPU via force_quiescent_state().
+
+o "j" is the low-order four hex digits of the jiffies counter.
+ Yes, Paul did run into a number of problems that turned out to
+ be due to the jiffies counter no longer counting. Why do you ask?
+
+o "nfqs" is the number of calls to force_quiescent_state() since
+ boot.
+
+o "nfqsng" is the number of useless calls to force_quiescent_state(),
+ where there wasn't actually a grace period active. This can
+ happen due to races. The number in parentheses is the difference
+ between "nfqs" and "nfqsng", or the number of times that
+ force_quiescent_state() actually did some real work.
+
+o "fqlh" is the number of calls to force_quiescent_state() that
+ exited immediately (without even being counted in nfqs above)
+ due to contention on ->fqslock.
+
+o Each element of the form "1/1 0:127 ^0" represents one struct
+ rcu_node. Each line represents one level of the hierarchy, from
+ root to leaves. It is best to think of the rcu_data structures
+ as forming yet another level after the leaves. Note that there
+ might be either one, two, or three levels of rcu_node structures,
+ depending on the relationship between CONFIG_RCU_FANOUT and
+ CONFIG_NR_CPUS.
+
+ o The numbers separated by the "/" are the qsmask followed
+ by the qsmaskinit. The qsmask will have one bit
+ set for each entity in the next lower level that
+ has not yet checked in for the current grace period.
+ The qsmaskinit will have one bit for each entity that is
+ currently expected to check in during each grace period.
+ The value of qsmaskinit is assigned to that of qsmask
+ at the beginning of each grace period.
+
+ For example, for "rcu", the qsmask of the first entry
+ of the lowest level is 0x14, meaning that we are still
+ waiting for CPUs 2 and 4 to check in for the current
+ grace period.
+
+ o The numbers separated by the ":" are the range of CPUs
+ served by this struct rcu_node. This can be helpful
+ in working out how the hierarchy is wired together.
+
+ For example, the first entry at the lowest level shows
+ "0:5", indicating that it covers CPUs 0 through 5.
+
+ o The number after the "^" indicates the bit in the
+ next higher level rcu_node structure that this
+ rcu_node structure corresponds to.
+
+ For example, the first entry at the lowest level shows
+ "^0", indicating that it corresponds to bit zero in
+ the first entry at the middle level.
diff --git a/arch/powerpc/platforms/pseries/rtasd.c b/arch/powerpc/platforms/pseries/rtasd.c
index c9ffd8c..d8e784a 100644
--- a/arch/powerpc/platforms/pseries/rtasd.c
+++ b/arch/powerpc/platforms/pseries/rtasd.c
@@ -208,6 +208,7 @@ void pSeries_log_error(char *buf, unsigned int err_type, int fatal)
break;
case ERR_TYPE_KERNEL_PANIC:
default:
+ WARN_ON_ONCE(!irqs_disabled()); /* @@@ DEBUG @@@ */
spin_unlock_irqrestore(&rtasd_log_lock, s);
return;
}
@@ -227,6 +228,7 @@ void pSeries_log_error(char *buf, unsigned int err_type, int fatal)
/* Check to see if we need to or have stopped logging */
if (fatal || !logging_enabled) {
logging_enabled = 0;
+ WARN_ON_ONCE(!irqs_disabled()); /* @@@ DEBUG @@@ */
spin_unlock_irqrestore(&rtasd_log_lock, s);
return;
}
@@ -249,11 +251,13 @@ void pSeries_log_error(char *buf, unsigned int err_type, int fatal)
else
rtas_log_start += 1;
+ WARN_ON_ONCE(!irqs_disabled()); /* @@@ DEBUG @@@ */
spin_unlock_irqrestore(&rtasd_log_lock, s);
wake_up_interruptible(&rtas_log_wait);
break;
case ERR_TYPE_KERNEL_PANIC:
default:
+ WARN_ON_ONCE(!irqs_disabled()); /* @@@ DEBUG @@@ */
spin_unlock_irqrestore(&rtasd_log_lock, s);
return;
}
diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
index 181006c..9b70b92 100644
--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -118,13 +118,17 @@ static inline void account_system_vtime(struct task_struct *tsk)
}
#endif
-#if defined(CONFIG_PREEMPT_RCU) && defined(CONFIG_NO_HZ)
+#if defined(CONFIG_NO_HZ) && !defined(CONFIG_CLASSIC_RCU)
extern void rcu_irq_enter(void);
extern void rcu_irq_exit(void);
+extern void rcu_nmi_enter(void);
+extern void rcu_nmi_exit(void);
#else
# define rcu_irq_enter() do { } while (0)
# define rcu_irq_exit() do { } while (0)
-#endif /* CONFIG_PREEMPT_RCU */
+# define rcu_nmi_enter() do { } while (0)
+# define rcu_nmi_exit() do { } while (0)
+#endif /* #if defined(CONFIG_NO_HZ) && !defined(CONFIG_CLASSIC_RCU) */
/*
* It is safe to do non-atomic ops on ->hardirq_context,
@@ -134,7 +138,6 @@ extern void rcu_irq_exit(void);
*/
#define __irq_enter() \
do { \
- rcu_irq_enter(); \
account_system_vtime(current); \
add_preempt_count(HARDIRQ_OFFSET); \
trace_hardirq_enter(); \
@@ -153,7 +156,6 @@ extern void irq_enter(void);
trace_hardirq_exit(); \
account_system_vtime(current); \
sub_preempt_count(HARDIRQ_OFFSET); \
- rcu_irq_exit(); \
} while (0)
/*
@@ -161,7 +163,7 @@ extern void irq_enter(void);
*/
extern void irq_exit(void);
-#define nmi_enter() do { lockdep_off(); __irq_enter(); } while (0)
-#define nmi_exit() do { __irq_exit(); lockdep_on(); } while (0)
+#define nmi_enter() do { lockdep_off(); rcu_nmi_enter(); __irq_enter(); } while (0)
+#define nmi_exit() do { __irq_exit(); rcu_nmi_exit(); lockdep_on(); } while (0)
#endif /* LINUX_HARDIRQ_H */
diff --git a/include/linux/rcuclassic.h b/include/linux/rcuclassic.h
index 4ab8436..b815f3c 100644
--- a/include/linux/rcuclassic.h
+++ b/include/linux/rcuclassic.h
@@ -164,4 +164,10 @@ extern long rcu_batches_completed_bh(void);
#define rcu_enter_nohz() do { } while (0)
#define rcu_exit_nohz() do { } while (0)
+/* A context switch is a grace period for rcuclassic. */
+static inline int rcu_blocking_is_gp(void)
+{
+ return num_online_cpus() == 1;
+}
+
#endif /* __LINUX_RCUCLASSIC_H */
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index e8b4039..a4320f7 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -52,11 +52,18 @@ struct rcu_head {
void (*func)(struct rcu_head *head);
};
-#ifdef CONFIG_CLASSIC_RCU
+/* Internal to kernel, but needed by rcupreempt.h. */
+extern int rcu_scheduler_active;
+
+#if defined(CONFIG_CLASSIC_RCU)
#include <linux/rcuclassic.h>
-#else /* #ifdef CONFIG_CLASSIC_RCU */
+#elif defined(CONFIG_TREE_RCU)
+#include <linux/rcutree.h>
+#elif defined(CONFIG_PREEMPT_RCU)
#include <linux/rcupreempt.h>
-#endif /* #else #ifdef CONFIG_CLASSIC_RCU */
+#else
+#error "Unknown RCU implementation specified to kernel configuration"
+#endif /* #else #if defined(CONFIG_CLASSIC_RCU) */
#define RCU_HEAD_INIT { .next = NULL, .func = NULL }
#define RCU_HEAD(head) struct rcu_head head = RCU_HEAD_INIT
@@ -183,6 +190,8 @@ void name(void) \
{ \
struct rcu_synchronize rcu; \
\
+ if (rcu_blocking_is_gp()) \
+ return; \
init_completion(&rcu.completion); \
/* Will wake me after RCU finished. */ \
func(&rcu.head, wakeme_after_rcu); \
@@ -251,6 +260,7 @@ extern void rcu_barrier_sched(void);
/* Internal to kernel */
extern void rcu_init(void);
+extern void rcu_scheduler_starting(void);
extern int rcu_needs_cpu(int cpu);
#endif /* __LINUX_RCUPDATE_H */
diff --git a/include/linux/rcupreempt.h b/include/linux/rcupreempt.h
index 0967f03..f4997ba 100644
--- a/include/linux/rcupreempt.h
+++ b/include/linux/rcupreempt.h
@@ -137,4 +137,19 @@ static inline void rcu_exit_nohz(void)
#define rcu_exit_nohz() do { } while (0)
#endif /* CONFIG_NO_HZ */
+/*
+ * A context switch is a grace period for rcupreempt synchronize_rcu()
+ * only during early boot, before the scheduler has been initialized.
+ * So, how the heck do we get a context switch? Well, if the caller
+ * invokes synchronize_rcu(), they are willing to accept a context
+ * switch, so we simply pretend that one happened.
+ *
+ * After boot, there might be a blocked or preempted task in an RCU
+ * read-side critical section, so we cannot then take the fastpath.
+ */
+static inline int rcu_blocking_is_gp(void)
+{
+ return num_online_cpus() == 1 && !rcu_scheduler_active;
+}
+
#endif /* __LINUX_RCUPREEMPT_H */
diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
new file mode 100644
index 0000000..6bab765
--- /dev/null
+++ b/include/linux/rcutree.h
@@ -0,0 +1,341 @@
+/*
+ * Read-Copy Update mechanism for mutual exclusion (tree-based version)
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright IBM Corporation, 2008
+ *
+ * Author: Dipankar Sarma <dipankar@...ibm.com>
+ * Paul E. McKenney <paulmck@...ux.vnet.ibm.com> Hierarchical algorithm
+ *
+ * Based on the original work by Paul McKenney <paulmck@...ibm.com>
+ * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
+ *
+ * For detailed explanation of Read-Copy Update mechanism see -
+ * Documentation/RCU
+ */
+
+#ifndef __LINUX_RCUTREE_H
+#define __LINUX_RCUTREE_H
+
+#include <linux/cache.h>
+#include <linux/spinlock.h>
+#include <linux/threads.h>
+#include <linux/percpu.h>
+#include <linux/cpumask.h>
+#include <linux/seqlock.h>
+
+/*
+ * Define shape of hierarchy based on NR_CPUS and CONFIG_RCU_FANOUT.
+ * In theory, it should be possible to add more levels straightforwardly.
+ * In practice, this has not been tested, so there is probably some
+ * bug somewhere.
+ */
+#define MAX_RCU_LVLS 3
+#define RCU_FANOUT (CONFIG_RCU_FANOUT)
+#define RCU_FANOUT_SQ (RCU_FANOUT * RCU_FANOUT)
+#define RCU_FANOUT_CUBE (RCU_FANOUT_SQ * RCU_FANOUT)
+
+#if NR_CPUS <= RCU_FANOUT
+# define NUM_RCU_LVLS 1
+# define NUM_RCU_LVL_0 1
+# define NUM_RCU_LVL_1 (NR_CPUS)
+# define NUM_RCU_LVL_2 0
+# define NUM_RCU_LVL_3 0
+#elif NR_CPUS <= RCU_FANOUT_SQ
+# define NUM_RCU_LVLS 2
+# define NUM_RCU_LVL_0 1
+# define NUM_RCU_LVL_1 (((NR_CPUS) + RCU_FANOUT - 1) / RCU_FANOUT)
+# define NUM_RCU_LVL_2 (NR_CPUS)
+# define NUM_RCU_LVL_3 0
+#elif NR_CPUS <= RCU_FANOUT_CUBE
+# define NUM_RCU_LVLS 3
+# define NUM_RCU_LVL_0 1
+# define NUM_RCU_LVL_1 (((NR_CPUS) + RCU_FANOUT_SQ - 1) / RCU_FANOUT_SQ)
+# define NUM_RCU_LVL_2 (((NR_CPUS) + (RCU_FANOUT) - 1) / (RCU_FANOUT))
+# define NUM_RCU_LVL_3 NR_CPUS
+#else
+# error "CONFIG_RCU_FANOUT insufficient for NR_CPUS"
+#endif /* #if (NR_CPUS) <= RCU_FANOUT */
+
+#define RCU_SUM (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2 + NUM_RCU_LVL_3)
+#define NUM_RCU_NODES (RCU_SUM - NR_CPUS)
+
+/*
+ * Dynticks per-CPU state.
+ */
+struct rcu_dynticks {
+ int dynticks_nesting; /* Track nesting level, sort of. */
+ int dynticks; /* Even value for dynticks-idle, else odd. */
+ int dynticks_nmi; /* Even value for either dynticks-idle or */
+ /* not in nmi handler, else odd. So this */
+ /* remains even for nmi from irq handler. */
+};
+
+/*
+ * Definition for node within the RCU grace-period-detection hierarchy.
+ */
+struct rcu_node {
+ spinlock_t lock;
+ unsigned long qsmask; /* CPUs or groups that need to switch in */
+ /* order for current grace period to proceed.*/
+ unsigned long qsmaskinit;
+ /* Per-GP initialization for qsmask. */
+ unsigned long grpmask; /* Mask to apply to parent qsmask. */
+ int grplo; /* lowest-numbered CPU or group here. */
+ int grphi; /* highest-numbered CPU or group here. */
+ u8 grpnum; /* CPU/group number for next level up. */
+ u8 level; /* root is at level 0. */
+ struct rcu_node *parent;
+} ____cacheline_internodealigned_in_smp;
+
+/* Index values for nxttail array in struct rcu_data. */
+#define RCU_DONE_TAIL 0 /* Also RCU_WAIT head. */
+#define RCU_WAIT_TAIL 1 /* Also RCU_NEXT_READY head. */
+#define RCU_NEXT_READY_TAIL 2 /* Also RCU_NEXT head. */
+#define RCU_NEXT_TAIL 3
+#define RCU_NEXT_SIZE 4
+
+/* Per-CPU data for read-copy update. */
+struct rcu_data {
+ /* 1) quiescent-state and grace-period handling : */
+ long completed; /* Track rsp->completed gp number */
+ /* in order to detect GP end. */
+ long gpnum; /* Highest gp number that this CPU */
+ /* is aware of having started. */
+ long passed_quiesc_completed;
+ /* Value of completed at time of qs. */
+ bool passed_quiesc; /* User-mode/idle loop etc. */
+ bool qs_pending; /* Core waits for quiesc state. */
+ bool beenonline; /* CPU online at least once. */
+ struct rcu_node *mynode; /* This CPU's leaf of hierarchy */
+ unsigned long grpmask; /* Mask to apply to leaf qsmask. */
+
+ /* 2) batch handling */
+ /*
+ * If nxtlist is not NULL, it is partitioned as follows.
+ * Any of the partitions might be empty, in which case the
+ * pointer to that partition will be equal to the pointer for
+ * the following partition. When the list is empty, all of
+ * the nxttail elements point to nxtlist, which is NULL.
+ *
+ * [*nxttail[RCU_NEXT_READY_TAIL], NULL = *nxttail[RCU_NEXT_TAIL]):
+ * Entries that might have arrived after current GP ended
+ * [*nxttail[RCU_WAIT_TAIL], *nxttail[RCU_NEXT_READY_TAIL]):
+ * Entries known to have arrived before current GP ended
+ * [*nxttail[RCU_DONE_TAIL], *nxttail[RCU_WAIT_TAIL]):
+ * Entries that batch # <= ->completed - 1: waiting for current GP
+ * [nxtlist, *nxttail[RCU_DONE_TAIL]):
+ * Entries that batch # <= ->completed
+ * The grace period for these entries has completed, and
+ * the other grace-period-completed entries may be moved
+ * here temporarily in rcu_process_callbacks().
+ */
+ struct rcu_head *nxtlist;
+ struct rcu_head **nxttail[RCU_NEXT_SIZE];
+ long qlen; /* # of queued callbacks */
+ long blimit; /* Upper limit on a processed batch */
+
+#ifdef CONFIG_NO_HZ
+ /* 3) dynticks interface. */
+ struct rcu_dynticks *dynticks; /* Shared per-CPU dynticks state. */
+ int dynticks_snap; /* Per-GP tracking for dynticks. */
+ int dynticks_nmi_snap; /* Per-GP tracking for dynticks_nmi. */
+#endif /* #ifdef CONFIG_NO_HZ */
+
+ /* 4) reasons this CPU needed to be kicked by force_quiescent_state */
+#ifdef CONFIG_NO_HZ
+ unsigned long dynticks_fqs; /* Kicked due to dynticks idle. */
+#endif /* #ifdef CONFIG_NO_HZ */
+ unsigned long offline_fqs; /* Kicked due to being offline. */
+ unsigned long resched_ipi; /* Sent a resched IPI. */
+
+ /* 5) __rcu_pending() statistics. */
+ long n_rcu_pending; /* rcu_pending() calls since boot. */
+ long n_rp_qs_pending;
+ long n_rp_cb_ready;
+ long n_rp_cpu_needs_gp;
+ long n_rp_gp_completed;
+ long n_rp_gp_started;
+ long n_rp_need_fqs;
+ long n_rp_need_nothing;
+
+ int cpu;
+};
+
+/* Values for signaled field in struct rcu_state. */
+#define RCU_GP_INIT 0 /* Grace period being initialized. */
+#define RCU_SAVE_DYNTICK 1 /* Need to scan dyntick state. */
+#define RCU_FORCE_QS 2 /* Need to force quiescent state. */
+#ifdef CONFIG_NO_HZ
+#define RCU_SIGNAL_INIT RCU_SAVE_DYNTICK
+#else /* #ifdef CONFIG_NO_HZ */
+#define RCU_SIGNAL_INIT RCU_FORCE_QS
+#endif /* #else #ifdef CONFIG_NO_HZ */
+
+#define RCU_JIFFIES_TILL_FORCE_QS 3 /* for rsp->jiffies_force_qs */
+#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
+#define RCU_SECONDS_TILL_STALL_CHECK (10 * HZ) /* for rsp->jiffies_stall */
+#define RCU_SECONDS_TILL_STALL_RECHECK (30 * HZ) /* for rsp->jiffies_stall */
+#define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time */
+ /* to take at least one */
+ /* scheduling clock irq */
+ /* before ratting on them. */
+
+#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
+
+/*
+ * RCU global state, including node hierarchy. This hierarchy is
+ * represented in "heap" form in a dense array. The root (first level)
+ * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second
+ * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]),
+ * and the third level in ->node[m+1] and following (->node[m+1] referenced
+ * by ->level[2]). The number of levels is determined by the number of
+ * CPUs and by CONFIG_RCU_FANOUT. Small systems will have a "hierarchy"
+ * consisting of a single rcu_node.
+ */
+struct rcu_state {
+ struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */
+ struct rcu_node *level[NUM_RCU_LVLS]; /* Hierarchy levels. */
+ u32 levelcnt[MAX_RCU_LVLS + 1]; /* # nodes in each level. */
+ u8 levelspread[NUM_RCU_LVLS]; /* kids/node in each level. */
+ struct rcu_data *rda[NR_CPUS]; /* array of rdp pointers. */
+
+ /* The following fields are guarded by the root rcu_node's lock. */
+
+ u8 signaled ____cacheline_internodealigned_in_smp;
+ /* Force QS state. */
+ long gpnum; /* Current gp number. */
+ long completed; /* # of last completed gp. */
+ spinlock_t onofflock; /* exclude on/offline and */
+ /* starting new GP. */
+ spinlock_t fqslock; /* Only one task forcing */
+ /* quiescent states. */
+ unsigned long jiffies_force_qs; /* Time at which to invoke */
+ /* force_quiescent_state(). */
+ unsigned long n_force_qs; /* Number of calls to */
+ /* force_quiescent_state(). */
+ unsigned long n_force_qs_lh; /* ~Number of calls leaving */
+ /* due to lock unavailable. */
+ unsigned long n_force_qs_ngp; /* Number of calls leaving */
+ /* due to no GP active. */
+#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
+ unsigned long gp_start; /* Time at which GP started, */
+ /* but in jiffies. */
+ unsigned long jiffies_stall; /* Time at which to check */
+ /* for CPU stalls. */
+#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
+#ifdef CONFIG_NO_HZ
+ long dynticks_completed; /* Value of completed @ snap. */
+#endif /* #ifdef CONFIG_NO_HZ */
+};
+
+extern struct rcu_state rcu_state;
+DECLARE_PER_CPU(struct rcu_data, rcu_data);
+
+extern struct rcu_state rcu_bh_state;
+DECLARE_PER_CPU(struct rcu_data, rcu_bh_data);
+
+/*
+ * Increment the quiescent state counter.
+ * The counter is a bit degenerated: We do not need to know
+ * how many quiescent states passed, just if there was at least
+ * one since the start of the grace period. Thus just a flag.
+ */
+static inline void rcu_qsctr_inc(int cpu)
+{
+ struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
+ rdp->passed_quiesc = 1;
+ rdp->passed_quiesc_completed = rdp->completed;
+}
+static inline void rcu_bh_qsctr_inc(int cpu)
+{
+ struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu);
+ rdp->passed_quiesc = 1;
+ rdp->passed_quiesc_completed = rdp->completed;
+}
+
+extern int rcu_pending(int cpu);
+extern int rcu_needs_cpu(int cpu);
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+extern struct lockdep_map rcu_lock_map;
+# define rcu_read_acquire() \
+ lock_acquire(&rcu_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_)
+# define rcu_read_release() lock_release(&rcu_lock_map, 1, _THIS_IP_)
+#else
+# define rcu_read_acquire() do { } while (0)
+# define rcu_read_release() do { } while (0)
+#endif
+
+static inline void __rcu_read_lock(void)
+{
+ preempt_disable();
+ __acquire(RCU);
+ rcu_read_acquire();
+}
+static inline void __rcu_read_unlock(void)
+{
+ rcu_read_release();
+ __release(RCU);
+ preempt_enable();
+}
+static inline void __rcu_read_lock_bh(void)
+{
+ local_bh_disable();
+ __acquire(RCU_BH);
+ rcu_read_acquire();
+}
+static inline void __rcu_read_unlock_bh(void)
+{
+ rcu_read_release();
+ __release(RCU_BH);
+ local_bh_enable();
+}
+
+#define __synchronize_sched() synchronize_rcu()
+
+#define call_rcu_sched(head, func) call_rcu(head, func)
+
+static inline void rcu_init_sched(void)
+{
+}
+
+extern void __rcu_init(void);
+extern void rcu_check_callbacks(int cpu, int user);
+extern void rcu_restart_cpu(int cpu);
+
+extern long rcu_batches_completed(void);
+extern long rcu_batches_completed_bh(void);
+
+#ifdef CONFIG_NO_HZ
+void rcu_enter_nohz(void);
+void rcu_exit_nohz(void);
+#else /* CONFIG_NO_HZ */
+static inline void rcu_enter_nohz(void)
+{
+}
+static inline void rcu_exit_nohz(void)
+{
+}
+#endif /* CONFIG_NO_HZ */
+
+/* A context switch is a grace period for rcutree. */
+static inline int rcu_blocking_is_gp(void)
+{
+ return num_online_cpus() == 1;
+}
+
+#endif /* __LINUX_RCUTREE_H */
diff --git a/init/Kconfig b/init/Kconfig
index c11da38..fdb0bcd 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -903,10 +903,16 @@ source "block/Kconfig"
config PREEMPT_NOTIFIERS
bool
-config CLASSIC_RCU
- def_bool !PREEMPT_RCU
+config TREE_RCU_TRACE
+ def_bool RCU_TRACE && TREE_RCU
+ select DEBUG_FS
help
- This option selects the classic RCU implementation that is
- designed for best read-side performance on non-realtime
- systems. Classic RCU is the default. Note that the
- PREEMPT_RCU symbol is used to select/deselect this option.
+ This option provides tracing for the TREE_RCU implementation,
+ permitting Makefile to trivially select kernel/rcutree_trace.c.
+
+config PREEMPT_RCU_TRACE
+ def_bool RCU_TRACE && PREEMPT_RCU
+ select DEBUG_FS
+ help
+ This option provides tracing for the PREEMPT_RCU implementation,
+ permitting Makefile to trivially select kernel/rcupreempt_trace.c.
diff --git a/init/main.c b/init/main.c
index 3820323..a05fdc7 100644
--- a/init/main.c
+++ b/init/main.c
@@ -102,7 +102,7 @@ static inline void mark_rodata_ro(void) { }
extern void tc_init(void);
#endif
-enum system_states system_state;
+enum system_states system_state __read_mostly;
EXPORT_SYMBOL(system_state);
/*
@@ -473,6 +473,7 @@ static void noinline __init_refok rest_init(void)
* at least once to get things moving:
*/
init_idle_bootup_task(current);
+ rcu_scheduler_starting();
preempt_enable_no_resched();
schedule();
preempt_disable();
diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt
index 9fdba03..463f297 100644
--- a/kernel/Kconfig.preempt
+++ b/kernel/Kconfig.preempt
@@ -52,10 +52,29 @@ config PREEMPT
endchoice
+choice
+ prompt "RCU Implementation"
+ default CLASSIC_RCU
+
+config CLASSIC_RCU
+ bool "Classic RCU"
+ help
+ This option selects the classic RCU implementation that is
+ designed for best read-side performance on non-realtime
+ systems.
+
+ Select this option if you are unsure.
+
+config TREE_RCU
+ bool "Tree-based hierarchical RCU"
+ help
+ This option selects the RCU implementation that is
+ designed for very large SMP system with hundreds or
+ thousands of CPUs.
+
config PREEMPT_RCU
bool "Preemptible RCU"
depends on PREEMPT
- default n
help
This option reduces the latency of the kernel by making certain
RCU sections preemptible. Normally RCU code is non-preemptible, if
@@ -64,16 +83,47 @@ config PREEMPT_RCU
now-naive assumptions about each RCU read-side critical section
remaining on a given CPU through its execution.
- Say N if you are unsure.
+endchoice
config RCU_TRACE
- bool "Enable tracing for RCU - currently stats in debugfs"
- depends on PREEMPT_RCU
- select DEBUG_FS
- default y
+ bool "Enable tracing for RCU"
+ depends on TREE_RCU || PREEMPT_RCU
help
This option provides tracing in RCU which presents stats
in debugfs for debugging RCU implementation.
Say Y here if you want to enable RCU tracing
Say N if you are unsure.
+
+config RCU_FANOUT
+ int "Tree-based hierarchical RCU fanout value"
+ range 2 64 if 64BIT
+ range 2 32 if !64BIT
+ depends on TREE_RCU
+ default 64 if 64BIT
+ default 32 if !64BIT
+ help
+ This option controls the fanout of hierarchical implementations
+ of RCU, allowing RCU to work efficiently on machines with
+ large numbers of CPUs. This value must be at least the cube
+ root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
+ systems and up to 262,144 for 64-bit systems.
+
+ Select a specific number if testing RCU itself.
+ Take the default if unsure.
+
+config RCU_FANOUT_EXACT
+ bool "Disable tree-based hierarchical RCU auto-balancing"
+ depends on TREE_RCU
+ default n
+ help
+ This option forces use of the exact RCU_FANOUT value specified,
+ regardless of imbalances in the hierarchy. This is useful for
+ testing RCU itself, and might one day be useful on systems with
+ strong NUMA behavior.
+
+ Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
+
+ Say n if unsure.
+
+
diff --git a/kernel/Makefile b/kernel/Makefile
index 4e1d7df..101e880 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -74,10 +74,10 @@ obj-$(CONFIG_GENERIC_HARDIRQS) += irq/
obj-$(CONFIG_SECCOMP) += seccomp.o
obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
obj-$(CONFIG_CLASSIC_RCU) += rcuclassic.o
+obj-$(CONFIG_TREE_RCU) += rcutree.o
obj-$(CONFIG_PREEMPT_RCU) += rcupreempt.o
-ifeq ($(CONFIG_PREEMPT_RCU),y)
-obj-$(CONFIG_RCU_TRACE) += rcupreempt_trace.o
-endif
+obj-$(CONFIG_TREE_RCU_TRACE) += rcutree_trace.o
+obj-$(CONFIG_PREEMPT_RCU_TRACE) += rcupreempt_trace.o
obj-$(CONFIG_RELAY) += relay.o
obj-$(CONFIG_SYSCTL) += utsname_sysctl.o
obj-$(CONFIG_TASK_DELAY_ACCT) += delayacct.o
diff --git a/kernel/rcuclassic.c b/kernel/rcuclassic.c
index aad93cd..0bcb212 100644
--- a/kernel/rcuclassic.c
+++ b/kernel/rcuclassic.c
@@ -518,8 +518,8 @@ int rcu_needs_cpu(int cpu)
void rcu_check_callbacks(int cpu, int user)
{
if (user ||
- (idle_cpu(cpu) && !in_softirq() &&
- hardirq_count() <= (1 << HARDIRQ_SHIFT))) {
+ (idle_cpu(cpu) && rcu_scheduler_active &&
+ !in_softirq() && hardirq_count() <= (1 << HARDIRQ_SHIFT))) {
/*
* Get here if this CPU took its interrupt from user
@@ -555,7 +555,7 @@ void rcu_check_callbacks(int cpu, int user)
raise_rcu_softirq();
}
-static void rcu_init_percpu_data(int cpu, struct rcu_ctrlblk *rcp,
+static void __cpuinit rcu_init_percpu_data(int cpu, struct rcu_ctrlblk *rcp,
struct rcu_data *rdp)
{
memset(rdp, 0, sizeof(*rdp));
diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index 467d594..2b317d1 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -44,6 +44,7 @@
#include <linux/cpu.h>
#include <linux/mutex.h>
#include <linux/module.h>
+#include <linux/kernel_stat.h>
enum rcu_barrier {
RCU_BARRIER_STD,
@@ -55,6 +56,7 @@ static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL};
static atomic_t rcu_barrier_cpu_count;
static DEFINE_MUTEX(rcu_barrier_mutex);
static struct completion rcu_barrier_completion;
+int rcu_scheduler_active __read_mostly;
/*
* Awaken the corresponding synchronize_rcu() instance now that a
@@ -167,3 +169,9 @@ void __init rcu_init(void)
__rcu_init();
}
+void rcu_scheduler_starting(void)
+{
+ WARN_ON(num_online_cpus() != 1);
+ WARN_ON(nr_context_switches() > 0);
+ rcu_scheduler_active = 1;
+}
diff --git a/kernel/rcupreempt.c b/kernel/rcupreempt.c
index 2782793..e353a01 100644
--- a/kernel/rcupreempt.c
+++ b/kernel/rcupreempt.c
@@ -559,6 +559,16 @@ void rcu_irq_exit(void)
}
}
+void rcu_nmi_enter(void)
+{
+ rcu_irq_enter();
+}
+
+void rcu_nmi_exit(void)
+{
+ rcu_irq_exit();
+}
+
static void dyntick_save_progress_counter(int cpu)
{
struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu);
@@ -1174,7 +1184,23 @@ EXPORT_SYMBOL_GPL(call_rcu_sched);
* in -rt this does -not- necessarily result in all currently executing
* interrupt -handlers- having completed.
*/
+<<<<<<< HEAD:kernel/rcupreempt.c
synchronize_rcu_xxx(__synchronize_sched, call_rcu_sched)
+=======
+void __synchronize_sched(void)
+{
+ struct rcu_synchronize rcu;
+
+ if (num_online_cpus() == 1)
+ return; /* blocking is gp if only one CPU! */
+
+ init_completion(&rcu.completion);
+ /* Will wake me after RCU finished. */
+ call_rcu_sched(&rcu.head, wakeme_after_rcu);
+ /* Wait for it. */
+ wait_for_completion(&rcu.completion);
+}
+>>>>>>> a682604... rcu: Teach RCU that idle task is not quiscent state at boot:kernel/rcupreempt.c
EXPORT_SYMBOL_GPL(__synchronize_sched);
/*
diff --git a/kernel/rcupreempt_trace.c b/kernel/rcupreempt_trace.c
index 5edf82c..def42e8 100644
--- a/kernel/rcupreempt_trace.c
+++ b/kernel/rcupreempt_trace.c
@@ -149,12 +149,12 @@ static void rcupreempt_trace_sum(struct rcupreempt_trace *sp)
sp->done_length += cp->done_length;
sp->done_add += cp->done_add;
sp->done_remove += cp->done_remove;
- atomic_set(&sp->done_invoked, atomic_read(&cp->done_invoked));
+ atomic_add(atomic_read(&cp->done_invoked), &sp->done_invoked);
sp->rcu_check_callbacks += cp->rcu_check_callbacks;
- atomic_set(&sp->rcu_try_flip_1,
- atomic_read(&cp->rcu_try_flip_1));
- atomic_set(&sp->rcu_try_flip_e1,
- atomic_read(&cp->rcu_try_flip_e1));
+ atomic_add(atomic_read(&cp->rcu_try_flip_1),
+ &sp->rcu_try_flip_1);
+ atomic_add(atomic_read(&cp->rcu_try_flip_e1),
+ &sp->rcu_try_flip_e1);
sp->rcu_try_flip_i1 += cp->rcu_try_flip_i1;
sp->rcu_try_flip_ie1 += cp->rcu_try_flip_ie1;
sp->rcu_try_flip_g1 += cp->rcu_try_flip_g1;
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
new file mode 100644
index 0000000..45f5365
--- /dev/null
+++ b/kernel/rcutree.c
@@ -0,0 +1,1534 @@
+/*
+ * Read-Copy Update mechanism for mutual exclusion
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright IBM Corporation, 2008
+ *
+ * Authors: Dipankar Sarma <dipankar@...ibm.com>
+ * Manfred Spraul <manfred@...orfullife.com>
+ * Paul E. McKenney <paulmck@...ux.vnet.ibm.com> Hierarchical version
+ *
+ * Based on the original work by Paul McKenney <paulmck@...ibm.com>
+ * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
+ *
+ * For detailed explanation of Read-Copy Update mechanism see -
+ * Documentation/RCU
+ */
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/spinlock.h>
+#include <linux/smp.h>
+#include <linux/rcupdate.h>
+#include <linux/interrupt.h>
+#include <linux/sched.h>
+#include <asm/atomic.h>
+#include <linux/bitops.h>
+#include <linux/module.h>
+#include <linux/completion.h>
+#include <linux/moduleparam.h>
+#include <linux/percpu.h>
+#include <linux/notifier.h>
+#include <linux/cpu.h>
+#include <linux/mutex.h>
+#include <linux/time.h>
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+static struct lock_class_key rcu_lock_key;
+struct lockdep_map rcu_lock_map =
+ STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key);
+EXPORT_SYMBOL_GPL(rcu_lock_map);
+#endif
+
+/* Data structures. */
+
+#define RCU_STATE_INITIALIZER(name) { \
+ .level = { &name.node[0] }, \
+ .levelcnt = { \
+ NUM_RCU_LVL_0, /* root of hierarchy. */ \
+ NUM_RCU_LVL_1, \
+ NUM_RCU_LVL_2, \
+ NUM_RCU_LVL_3, /* == MAX_RCU_LVLS */ \
+ }, \
+ .signaled = RCU_SIGNAL_INIT, \
+ .gpnum = -300, \
+ .completed = -300, \
+ .onofflock = __SPIN_LOCK_UNLOCKED(&name.onofflock), \
+ .fqslock = __SPIN_LOCK_UNLOCKED(&name.fqslock), \
+ .n_force_qs = 0, \
+ .n_force_qs_ngp = 0, \
+}
+
+struct rcu_state rcu_state = RCU_STATE_INITIALIZER(rcu_state);
+DEFINE_PER_CPU(struct rcu_data, rcu_data);
+
+struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh_state);
+DEFINE_PER_CPU(struct rcu_data, rcu_bh_data);
+
+#ifdef CONFIG_NO_HZ
+DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {
+ .dynticks_nesting = 1,
+ .dynticks = 1,
+};
+#endif /* #ifdef CONFIG_NO_HZ */
+
+static int blimit = 10; /* Maximum callbacks per softirq. */
+static int qhimark = 10000; /* If this many pending, ignore blimit. */
+static int qlowmark = 100; /* Once only this many pending, use blimit. */
+
+static void force_quiescent_state(struct rcu_state *rsp, int relaxed);
+
+/*
+ * Return the number of RCU batches processed thus far for debug & stats.
+ */
+long rcu_batches_completed(void)
+{
+ return rcu_state.completed;
+}
+EXPORT_SYMBOL_GPL(rcu_batches_completed);
+
+/*
+ * Return the number of RCU BH batches processed thus far for debug & stats.
+ */
+long rcu_batches_completed_bh(void)
+{
+ return rcu_bh_state.completed;
+}
+EXPORT_SYMBOL_GPL(rcu_batches_completed_bh);
+
+/*
+ * Does the CPU have callbacks ready to be invoked?
+ */
+static int
+cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp)
+{
+ return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL];
+}
+
+/*
+ * Does the current CPU require a yet-as-unscheduled grace period?
+ */
+static int
+cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp)
+{
+ /* ACCESS_ONCE() because we are accessing outside of lock. */
+ return *rdp->nxttail[RCU_DONE_TAIL] &&
+ ACCESS_ONCE(rsp->completed) == ACCESS_ONCE(rsp->gpnum);
+}
+
+/*
+ * Return the root node of the specified rcu_state structure.
+ */
+static struct rcu_node *rcu_get_root(struct rcu_state *rsp)
+{
+ return &rsp->node[0];
+}
+
+#ifdef CONFIG_SMP
+
+/*
+ * If the specified CPU is offline, tell the caller that it is in
+ * a quiescent state. Otherwise, whack it with a reschedule IPI.
+ * Grace periods can end up waiting on an offline CPU when that
+ * CPU is in the process of coming online -- it will be added to the
+ * rcu_node bitmasks before it actually makes it online. The same thing
+ * can happen while a CPU is in the process of coming online. Because this
+ * race is quite rare, we check for it after detecting that the grace
+ * period has been delayed rather than checking each and every CPU
+ * each and every time we start a new grace period.
+ */
+static int rcu_implicit_offline_qs(struct rcu_data *rdp)
+{
+ /*
+ * If the CPU is offline, it is in a quiescent state. We can
+ * trust its state not to change because interrupts are disabled.
+ */
+ if (cpu_is_offline(rdp->cpu)) {
+ rdp->offline_fqs++;
+ return 1;
+ }
+
+ /* The CPU is online, so send it a reschedule IPI. */
+ if (rdp->cpu != smp_processor_id())
+ smp_send_reschedule(rdp->cpu);
+ else
+ set_need_resched();
+ rdp->resched_ipi++;
+ return 0;
+}
+
+#endif /* #ifdef CONFIG_SMP */
+
+#ifdef CONFIG_NO_HZ
+static DEFINE_RATELIMIT_STATE(rcu_rs, 10 * HZ, 5);
+
+/**
+ * rcu_enter_nohz - inform RCU that current CPU is entering nohz
+ *
+ * Enter nohz mode, in other words, -leave- the mode in which RCU
+ * read-side critical sections can occur. (Though RCU read-side
+ * critical sections can occur in irq handlers in nohz mode, a possibility
+ * handled by rcu_irq_enter() and rcu_irq_exit()).
+ */
+void rcu_enter_nohz(void)
+{
+ unsigned long flags;
+ struct rcu_dynticks *rdtp;
+
+ smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */
+ local_irq_save(flags);
+ rdtp = &__get_cpu_var(rcu_dynticks);
+ rdtp->dynticks++;
+ rdtp->dynticks_nesting--;
+ WARN_ON_RATELIMIT(rdtp->dynticks & 0x1, &rcu_rs);
+ local_irq_restore(flags);
+}
+
+/*
+ * rcu_exit_nohz - inform RCU that current CPU is leaving nohz
+ *
+ * Exit nohz mode, in other words, -enter- the mode in which RCU
+ * read-side critical sections normally occur.
+ */
+void rcu_exit_nohz(void)
+{
+ unsigned long flags;
+ struct rcu_dynticks *rdtp;
+
+ local_irq_save(flags);
+ rdtp = &__get_cpu_var(rcu_dynticks);
+ rdtp->dynticks++;
+ rdtp->dynticks_nesting++;
+ WARN_ON_RATELIMIT(!(rdtp->dynticks & 0x1), &rcu_rs);
+ local_irq_restore(flags);
+ smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */
+}
+
+/**
+ * rcu_nmi_enter - inform RCU of entry to NMI context
+ *
+ * If the CPU was idle with dynamic ticks active, and there is no
+ * irq handler running, this updates rdtp->dynticks_nmi to let the
+ * RCU grace-period handling know that the CPU is active.
+ */
+void rcu_nmi_enter(void)
+{
+ struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
+
+ if (rdtp->dynticks & 0x1)
+ return;
+ rdtp->dynticks_nmi++;
+ WARN_ON_RATELIMIT(!(rdtp->dynticks_nmi & 0x1), &rcu_rs);
+ smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */
+}
+
+/**
+ * rcu_nmi_exit - inform RCU of exit from NMI context
+ *
+ * If the CPU was idle with dynamic ticks active, and there is no
+ * irq handler running, this updates rdtp->dynticks_nmi to let the
+ * RCU grace-period handling know that the CPU is no longer active.
+ */
+void rcu_nmi_exit(void)
+{
+ struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
+
+ if (rdtp->dynticks & 0x1)
+ return;
+ smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */
+ rdtp->dynticks_nmi++;
+ WARN_ON_RATELIMIT(rdtp->dynticks_nmi & 0x1, &rcu_rs);
+}
+
+/**
+ * rcu_irq_enter - inform RCU of entry to hard irq context
+ *
+ * If the CPU was idle with dynamic ticks active, this updates the
+ * rdtp->dynticks to let the RCU handling know that the CPU is active.
+ */
+void rcu_irq_enter(void)
+{
+ struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
+
+ if (rdtp->dynticks_nesting++)
+ return;
+ rdtp->dynticks++;
+ WARN_ON_RATELIMIT(!(rdtp->dynticks & 0x1), &rcu_rs);
+ smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */
+}
+
+/**
+ * rcu_irq_exit - inform RCU of exit from hard irq context
+ *
+ * If the CPU was idle with dynamic ticks active, update the rdp->dynticks
+ * to put let the RCU handling be aware that the CPU is going back to idle
+ * with no ticks.
+ */
+void rcu_irq_exit(void)
+{
+ struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks);
+
+ if (--rdtp->dynticks_nesting)
+ return;
+ smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */
+ rdtp->dynticks++;
+ WARN_ON_RATELIMIT(rdtp->dynticks & 0x1, &rcu_rs);
+
+ /* If the interrupt queued a callback, get out of dyntick mode. */
+ if (__get_cpu_var(rcu_data).nxtlist ||
+ __get_cpu_var(rcu_bh_data).nxtlist)
+ set_need_resched();
+}
+
+/*
+ * Record the specified "completed" value, which is later used to validate
+ * dynticks counter manipulations. Specify "rsp->completed - 1" to
+ * unconditionally invalidate any future dynticks manipulations (which is
+ * useful at the beginning of a grace period).
+ */
+static void dyntick_record_completed(struct rcu_state *rsp, long comp)
+{
+ rsp->dynticks_completed = comp;
+}
+
+#ifdef CONFIG_SMP
+
+/*
+ * Recall the previously recorded value of the completion for dynticks.
+ */
+static long dyntick_recall_completed(struct rcu_state *rsp)
+{
+ return rsp->dynticks_completed;
+}
+
+/*
+ * Snapshot the specified CPU's dynticks counter so that we can later
+ * credit them with an implicit quiescent state. Return 1 if this CPU
+ * is already in a quiescent state courtesy of dynticks idle mode.
+ */
+static int dyntick_save_progress_counter(struct rcu_data *rdp)
+{
+ int ret;
+ int snap;
+ int snap_nmi;
+
+ snap = rdp->dynticks->dynticks;
+ snap_nmi = rdp->dynticks->dynticks_nmi;
+ smp_mb(); /* Order sampling of snap with end of grace period. */
+ rdp->dynticks_snap = snap;
+ rdp->dynticks_nmi_snap = snap_nmi;
+ ret = ((snap & 0x1) == 0) && ((snap_nmi & 0x1) == 0);
+ if (ret)
+ rdp->dynticks_fqs++;
+ return ret;
+}
+
+/*
+ * Return true if the specified CPU has passed through a quiescent
+ * state by virtue of being in or having passed through an dynticks
+ * idle state since the last call to dyntick_save_progress_counter()
+ * for this same CPU.
+ */
+static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
+{
+ long curr;
+ long curr_nmi;
+ long snap;
+ long snap_nmi;
+
+ curr = rdp->dynticks->dynticks;
+ snap = rdp->dynticks_snap;
+ curr_nmi = rdp->dynticks->dynticks_nmi;
+ snap_nmi = rdp->dynticks_nmi_snap;
+ smp_mb(); /* force ordering with cpu entering/leaving dynticks. */
+
+ /*
+ * If the CPU passed through or entered a dynticks idle phase with
+ * no active irq/NMI handlers, then we can safely pretend that the CPU
+ * already acknowledged the request to pass through a quiescent
+ * state. Either way, that CPU cannot possibly be in an RCU
+ * read-side critical section that started before the beginning
+ * of the current RCU grace period.
+ */
+ if ((curr != snap || (curr & 0x1) == 0) &&
+ (curr_nmi != snap_nmi || (curr_nmi & 0x1) == 0)) {
+ rdp->dynticks_fqs++;
+ return 1;
+ }
+
+ /* Go check for the CPU being offline. */
+ return rcu_implicit_offline_qs(rdp);
+}
+
+#endif /* #ifdef CONFIG_SMP */
+
+#else /* #ifdef CONFIG_NO_HZ */
+
+static void dyntick_record_completed(struct rcu_state *rsp, long comp)
+{
+}
+
+#ifdef CONFIG_SMP
+
+/*
+ * If there are no dynticks, then the only way that a CPU can passively
+ * be in a quiescent state is to be offline. Unlike dynticks idle, which
+ * is a point in time during the prior (already finished) grace period,
+ * an offline CPU is always in a quiescent state, and thus can be
+ * unconditionally applied. So just return the current value of completed.
+ */
+static long dyntick_recall_completed(struct rcu_state *rsp)
+{
+ return rsp->completed;
+}
+
+static int dyntick_save_progress_counter(struct rcu_data *rdp)
+{
+ return 0;
+}
+
+static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
+{
+ return rcu_implicit_offline_qs(rdp);
+}
+
+#endif /* #ifdef CONFIG_SMP */
+
+#endif /* #else #ifdef CONFIG_NO_HZ */
+
+#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
+
+static void record_gp_stall_check_time(struct rcu_state *rsp)
+{
+ rsp->gp_start = jiffies;
+ rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_CHECK;
+}
+
+static void print_other_cpu_stall(struct rcu_state *rsp)
+{
+ int cpu;
+ long delta;
+ unsigned long flags;
+ struct rcu_node *rnp = rcu_get_root(rsp);
+ struct rcu_node *rnp_cur = rsp->level[NUM_RCU_LVLS - 1];
+ struct rcu_node *rnp_end = &rsp->node[NUM_RCU_NODES];
+
+ /* Only let one CPU complain about others per time interval. */
+
+ spin_lock_irqsave(&rnp->lock, flags);
+ delta = jiffies - rsp->jiffies_stall;
+ if (delta < RCU_STALL_RAT_DELAY || rsp->gpnum == rsp->completed) {
+ spin_unlock_irqrestore(&rnp->lock, flags);
+ return;
+ }
+ rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_RECHECK;
+ spin_unlock_irqrestore(&rnp->lock, flags);
+
+ /* OK, time to rat on our buddy... */
+
+ printk(KERN_ERR "INFO: RCU detected CPU stalls:");
+ for (; rnp_cur < rnp_end; rnp_cur++) {
+ if (rnp_cur->qsmask == 0)
+ continue;
+ for (cpu = 0; cpu <= rnp_cur->grphi - rnp_cur->grplo; cpu++)
+ if (rnp_cur->qsmask & (1UL << cpu))
+ printk(" %d", rnp_cur->grplo + cpu);
+ }
+ printk(" (detected by %d, t=%ld jiffies)\n",
+ smp_processor_id(), (long)(jiffies - rsp->gp_start));
+ force_quiescent_state(rsp, 0); /* Kick them all. */
+}
+
+static void print_cpu_stall(struct rcu_state *rsp)
+{
+ unsigned long flags;
+ struct rcu_node *rnp = rcu_get_root(rsp);
+
+ printk(KERN_ERR "INFO: RCU detected CPU %d stall (t=%lu jiffies)\n",
+ smp_processor_id(), jiffies - rsp->gp_start);
+ dump_stack();
+ spin_lock_irqsave(&rnp->lock, flags);
+ if ((long)(jiffies - rsp->jiffies_stall) >= 0)
+ rsp->jiffies_stall =
+ jiffies + RCU_SECONDS_TILL_STALL_RECHECK;
+ spin_unlock_irqrestore(&rnp->lock, flags);
+ set_need_resched(); /* kick ourselves to get things going. */
+}
+
+static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
+{
+ long delta;
+ struct rcu_node *rnp;
+
+ delta = jiffies - rsp->jiffies_stall;
+ rnp = rdp->mynode;
+ if ((rnp->qsmask & rdp->grpmask) && delta >= 0) {
+
+ /* We haven't checked in, so go dump stack. */
+ print_cpu_stall(rsp);
+
+ } else if (rsp->gpnum != rsp->completed &&
+ delta >= RCU_STALL_RAT_DELAY) {
+
+ /* They had two time units to dump stack, so complain. */
+ print_other_cpu_stall(rsp);
+ }
+}
+
+#else /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
+
+static void record_gp_stall_check_time(struct rcu_state *rsp)
+{
+}
+
+static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
+{
+}
+
+#endif /* #else #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
+
+/*
+ * Update CPU-local rcu_data state to record the newly noticed grace period.
+ * This is used both when we started the grace period and when we notice
+ * that someone else started the grace period.
+ */
+static void note_new_gpnum(struct rcu_state *rsp, struct rcu_data *rdp)
+{
+ rdp->qs_pending = 1;
+ rdp->passed_quiesc = 0;
+ rdp->gpnum = rsp->gpnum;
+}
+
+/*
+ * Did someone else start a new RCU grace period start since we last
+ * checked? Update local state appropriately if so. Must be called
+ * on the CPU corresponding to rdp.
+ */
+static int
+check_for_new_grace_period(struct rcu_state *rsp, struct rcu_data *rdp)
+{
+ unsigned long flags;
+ int ret = 0;
+
+ local_irq_save(flags);
+ if (rdp->gpnum != rsp->gpnum) {
+ note_new_gpnum(rsp, rdp);
+ ret = 1;
+ }
+ local_irq_restore(flags);
+ return ret;
+}
+
+/*
+ * Start a new RCU grace period if warranted, re-initializing the hierarchy
+ * in preparation for detecting the next grace period. The caller must hold
+ * the root node's ->lock, which is released before return. Hard irqs must
+ * be disabled.
+ */
+static void
+rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
+ __releases(rcu_get_root(rsp)->lock)
+{
+ struct rcu_data *rdp = rsp->rda[smp_processor_id()];
+ struct rcu_node *rnp = rcu_get_root(rsp);
+ struct rcu_node *rnp_cur;
+ struct rcu_node *rnp_end;
+
+ if (!cpu_needs_another_gp(rsp, rdp)) {
+ spin_unlock_irqrestore(&rnp->lock, flags);
+ return;
+ }
+
+ /* Advance to a new grace period and initialize state. */
+ rsp->gpnum++;
+ rsp->signaled = RCU_GP_INIT; /* Hold off force_quiescent_state. */
+ rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS;
+ record_gp_stall_check_time(rsp);
+ dyntick_record_completed(rsp, rsp->completed - 1);
+ note_new_gpnum(rsp, rdp);
+
+ /*
+ * Because we are first, we know that all our callbacks will
+ * be covered by this upcoming grace period, even the ones
+ * that were registered arbitrarily recently.
+ */
+ rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
+ rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
+
+ /* Special-case the common single-level case. */
+ if (NUM_RCU_NODES == 1) {
+ rnp->qsmask = rnp->qsmaskinit;
+ rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state OK. */
+ spin_unlock_irqrestore(&rnp->lock, flags);
+ return;
+ }
+
+ spin_unlock(&rnp->lock); /* leave irqs disabled. */
+
+
+ /* Exclude any concurrent CPU-hotplug operations. */
+ spin_lock(&rsp->onofflock); /* irqs already disabled. */
+
+ /*
+ * Set the quiescent-state-needed bits in all the non-leaf RCU
+ * nodes for all currently online CPUs. This operation relies
+ * on the layout of the hierarchy within the rsp->node[] array.
+ * Note that other CPUs will access only the leaves of the
+ * hierarchy, which still indicate that no grace period is in
+ * progress. In addition, we have excluded CPU-hotplug operations.
+ *
+ * We therefore do not need to hold any locks. Any required
+ * memory barriers will be supplied by the locks guarding the
+ * leaf rcu_nodes in the hierarchy.
+ */
+
+ rnp_end = rsp->level[NUM_RCU_LVLS - 1];
+ for (rnp_cur = &rsp->node[0]; rnp_cur < rnp_end; rnp_cur++)
+ rnp_cur->qsmask = rnp_cur->qsmaskinit;
+
+ /*
+ * Now set up the leaf nodes. Here we must be careful. First,
+ * we need to hold the lock in order to exclude other CPUs, which
+ * might be contending for the leaf nodes' locks. Second, as
+ * soon as we initialize a given leaf node, its CPUs might run
+ * up the rest of the hierarchy. We must therefore acquire locks
+ * for each node that we touch during this stage. (But we still
+ * are excluding CPU-hotplug operations.)
+ *
+ * Note that the grace period cannot complete until we finish
+ * the initialization process, as there will be at least one
+ * qsmask bit set in the root node until that time, namely the
+ * one corresponding to this CPU.
+ */
+ rnp_end = &rsp->node[NUM_RCU_NODES];
+ rnp_cur = rsp->level[NUM_RCU_LVLS - 1];
+ for (; rnp_cur < rnp_end; rnp_cur++) {
+ spin_lock(&rnp_cur->lock); /* irqs already disabled. */
+ rnp_cur->qsmask = rnp_cur->qsmaskinit;
+ spin_unlock(&rnp_cur->lock); /* irqs already disabled. */
+ }
+
+ rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state now OK. */
+ spin_unlock_irqrestore(&rsp->onofflock, flags);
+}
+
+/*
+ * Advance this CPU's callbacks, but only if the current grace period
+ * has ended. This may be called only from the CPU to whom the rdp
+ * belongs.
+ */
+static void
+rcu_process_gp_end(struct rcu_state *rsp, struct rcu_data *rdp)
+{
+ long completed_snap;
+ unsigned long flags;
+
+ local_irq_save(flags);
+ completed_snap = ACCESS_ONCE(rsp->completed); /* outside of lock. */
+
+ /* Did another grace period end? */
+ if (rdp->completed != completed_snap) {
+
+ /* Advance callbacks. No harm if list empty. */
+ rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[RCU_WAIT_TAIL];
+ rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_READY_TAIL];
+ rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
+
+ /* Remember that we saw this grace-period completion. */
+ rdp->completed = completed_snap;
+ }
+ local_irq_restore(flags);
+}
+
+/*
+ * Similar to cpu_quiet(), for which it is a helper function. Allows
+ * a group of CPUs to be quieted at one go, though all the CPUs in the
+ * group must be represented by the same leaf rcu_node structure.
+ * That structure's lock must be held upon entry, and it is released
+ * before return.
+ */
+static void
+cpu_quiet_msk(unsigned long mask, struct rcu_state *rsp, struct rcu_node *rnp,
+ unsigned long flags)
+ __releases(rnp->lock)
+{
+ /* Walk up the rcu_node hierarchy. */
+ for (;;) {
+ if (!(rnp->qsmask & mask)) {
+
+ /* Our bit has already been cleared, so done. */
+ spin_unlock_irqrestore(&rnp->lock, flags);
+ return;
+ }
+ rnp->qsmask &= ~mask;
+ if (rnp->qsmask != 0) {
+
+ /* Other bits still set at this level, so done. */
+ spin_unlock_irqrestore(&rnp->lock, flags);
+ return;
+ }
+ mask = rnp->grpmask;
+ if (rnp->parent == NULL) {
+
+ /* No more levels. Exit loop holding root lock. */
+
+ break;
+ }
+ spin_unlock_irqrestore(&rnp->lock, flags);
+ rnp = rnp->parent;
+ spin_lock_irqsave(&rnp->lock, flags);
+ }
+
+ /*
+ * Get here if we are the last CPU to pass through a quiescent
+ * state for this grace period. Clean up and let rcu_start_gp()
+ * start up the next grace period if one is needed. Note that
+ * we still hold rnp->lock, as required by rcu_start_gp(), which
+ * will release it.
+ */
+ rsp->completed = rsp->gpnum;
+ rcu_process_gp_end(rsp, rsp->rda[smp_processor_id()]);
+ rcu_start_gp(rsp, flags); /* releases rnp->lock. */
+}
+
+/*
+ * Record a quiescent state for the specified CPU, which must either be
+ * the current CPU or an offline CPU. The lastcomp argument is used to
+ * make sure we are still in the grace period of interest. We don't want
+ * to end the current grace period based on quiescent states detected in
+ * an earlier grace period!
+ */
+static void
+cpu_quiet(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastcomp)
+{
+ unsigned long flags;
+ unsigned long mask;
+ struct rcu_node *rnp;
+
+ rnp = rdp->mynode;
+ spin_lock_irqsave(&rnp->lock, flags);
+ if (lastcomp != ACCESS_ONCE(rsp->completed)) {
+
+ /*
+ * Someone beat us to it for this grace period, so leave.
+ * The race with GP start is resolved by the fact that we
+ * hold the leaf rcu_node lock, so that the per-CPU bits
+ * cannot yet be initialized -- so we would simply find our
+ * CPU's bit already cleared in cpu_quiet_msk() if this race
+ * occurred.
+ */
+ rdp->passed_quiesc = 0; /* try again later! */
+ spin_unlock_irqrestore(&rnp->lock, flags);
+ return;
+ }
+ mask = rdp->grpmask;
+ if ((rnp->qsmask & mask) == 0) {
+ spin_unlock_irqrestore(&rnp->lock, flags);
+ } else {
+ rdp->qs_pending = 0;
+
+ /*
+ * This GP can't end until cpu checks in, so all of our
+ * callbacks can be processed during the next GP.
+ */
+ rdp = rsp->rda[smp_processor_id()];
+ rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
+
+ cpu_quiet_msk(mask, rsp, rnp, flags); /* releases rnp->lock */
+ }
+}
+
+/*
+ * Check to see if there is a new grace period of which this CPU
+ * is not yet aware, and if so, set up local rcu_data state for it.
+ * Otherwise, see if this CPU has just passed through its first
+ * quiescent state for this grace period, and record that fact if so.
+ */
+static void
+rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp)
+{
+ /* If there is now a new grace period, record and return. */
+ if (check_for_new_grace_period(rsp, rdp))
+ return;
+
+ /*
+ * Does this CPU still need to do its part for current grace period?
+ * If no, return and let the other CPUs do their part as well.
+ */
+ if (!rdp->qs_pending)
+ return;
+
+ /*
+ * Was there a quiescent state since the beginning of the grace
+ * period? If no, then exit and wait for the next call.
+ */
+ if (!rdp->passed_quiesc)
+ return;
+
+ /* Tell RCU we are done (but cpu_quiet() will be the judge of that). */
+ cpu_quiet(rdp->cpu, rsp, rdp, rdp->passed_quiesc_completed);
+}
+
+#ifdef CONFIG_HOTPLUG_CPU
+
+/*
+ * Remove the outgoing CPU from the bitmasks in the rcu_node hierarchy
+ * and move all callbacks from the outgoing CPU to the current one.
+ */
+static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
+{
+ int i;
+ unsigned long flags;
+ long lastcomp;
+ unsigned long mask;
+ struct rcu_data *rdp = rsp->rda[cpu];
+ struct rcu_data *rdp_me;
+ struct rcu_node *rnp;
+
+ /* Exclude any attempts to start a new grace period. */
+ spin_lock_irqsave(&rsp->onofflock, flags);
+
+ /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */
+ rnp = rdp->mynode;
+ mask = rdp->grpmask; /* rnp->grplo is constant. */
+ do {
+ spin_lock(&rnp->lock); /* irqs already disabled. */
+ rnp->qsmaskinit &= ~mask;
+ if (rnp->qsmaskinit != 0) {
+ spin_unlock(&rnp->lock); /* irqs already disabled. */
+ break;
+ }
+ mask = rnp->grpmask;
+ spin_unlock(&rnp->lock); /* irqs already disabled. */
+ rnp = rnp->parent;
+ } while (rnp != NULL);
+ lastcomp = rsp->completed;
+
+ spin_unlock(&rsp->onofflock); /* irqs remain disabled. */
+
+ /* Being offline is a quiescent state, so go record it. */
+ cpu_quiet(cpu, rsp, rdp, lastcomp);
+
+ /*
+ * Move callbacks from the outgoing CPU to the running CPU.
+ * Note that the outgoing CPU is now quiscent, so it is now
+ * (uncharacteristically) safe to access it rcu_data structure.
+ * Note also that we must carefully retain the order of the
+ * outgoing CPU's callbacks in order for rcu_barrier() to work
+ * correctly. Finally, note that we start all the callbacks
+ * afresh, even those that have passed through a grace period
+ * and are therefore ready to invoke. The theory is that hotplug
+ * events are rare, and that if they are frequent enough to
+ * indefinitely delay callbacks, you have far worse things to
+ * be worrying about.
+ */
+ rdp_me = rsp->rda[smp_processor_id()];
+ if (rdp->nxtlist != NULL) {
+ *rdp_me->nxttail[RCU_NEXT_TAIL] = rdp->nxtlist;
+ rdp_me->nxttail[RCU_NEXT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
+ rdp->nxtlist = NULL;
+ for (i = 0; i < RCU_NEXT_SIZE; i++)
+ rdp->nxttail[i] = &rdp->nxtlist;
+ rdp_me->qlen += rdp->qlen;
+ rdp->qlen = 0;
+ }
+ local_irq_restore(flags);
+}
+
+/*
+ * Remove the specified CPU from the RCU hierarchy and move any pending
+ * callbacks that it might have to the current CPU. This code assumes
+ * that at least one CPU in the system will remain running at all times.
+ * Any attempt to offline -all- CPUs is likely to strand RCU callbacks.
+ */
+static void rcu_offline_cpu(int cpu)
+{
+ __rcu_offline_cpu(cpu, &rcu_state);
+ __rcu_offline_cpu(cpu, &rcu_bh_state);
+}
+
+#else /* #ifdef CONFIG_HOTPLUG_CPU */
+
+static void rcu_offline_cpu(int cpu)
+{
+}
+
+#endif /* #else #ifdef CONFIG_HOTPLUG_CPU */
+
+/*
+ * Invoke any RCU callbacks that have made it to the end of their grace
+ * period. Thottle as specified by rdp->blimit.
+ */
+static void rcu_do_batch(struct rcu_data *rdp)
+{
+ unsigned long flags;
+ struct rcu_head *next, *list, **tail;
+ int count;
+
+ /* If no callbacks are ready, just return.*/
+ if (!cpu_has_callbacks_ready_to_invoke(rdp))
+ return;
+
+ /*
+ * Extract the list of ready callbacks, disabling to prevent
+ * races with call_rcu() from interrupt handlers.
+ */
+ local_irq_save(flags);
+ list = rdp->nxtlist;
+ rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL];
+ *rdp->nxttail[RCU_DONE_TAIL] = NULL;
+ tail = rdp->nxttail[RCU_DONE_TAIL];
+ for (count = RCU_NEXT_SIZE - 1; count >= 0; count--)
+ if (rdp->nxttail[count] == rdp->nxttail[RCU_DONE_TAIL])
+ rdp->nxttail[count] = &rdp->nxtlist;
+ local_irq_restore(flags);
+
+ /* Invoke callbacks. */
+ count = 0;
+ while (list) {
+ next = list->next;
+ prefetch(next);
+ list->func(list);
+ list = next;
+ if (++count >= rdp->blimit)
+ break;
+ }
+
+ local_irq_save(flags);
+
+ /* Update count, and requeue any remaining callbacks. */
+ rdp->qlen -= count;
+ if (list != NULL) {
+ *tail = rdp->nxtlist;
+ rdp->nxtlist = list;
+ for (count = 0; count < RCU_NEXT_SIZE; count++)
+ if (&rdp->nxtlist == rdp->nxttail[count])
+ rdp->nxttail[count] = tail;
+ else
+ break;
+ }
+
+ /* Reinstate batch limit if we have worked down the excess. */
+ if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark)
+ rdp->blimit = blimit;
+
+ local_irq_restore(flags);
+
+ /* Re-raise the RCU softirq if there are callbacks remaining. */
+ if (cpu_has_callbacks_ready_to_invoke(rdp))
+ raise_softirq(RCU_SOFTIRQ);
+}
+
+/*
+ * Check to see if this CPU is in a non-context-switch quiescent state
+ * (user mode or idle loop for rcu, non-softirq execution for rcu_bh).
+ * Also schedule the RCU softirq handler.
+ *
+ * This function must be called with hardirqs disabled. It is normally
+ * invoked from the scheduling-clock interrupt. If rcu_pending returns
+ * false, there is no point in invoking rcu_check_callbacks().
+ */
+void rcu_check_callbacks(int cpu, int user)
+{
+ if (user ||
+ (idle_cpu(cpu) && rcu_scheduler_active &&
+ !in_softirq() && hardirq_count() <= (1 << HARDIRQ_SHIFT))) {
+
+ /*
+ * Get here if this CPU took its interrupt from user
+ * mode or from the idle loop, and if this is not a
+ * nested interrupt. In this case, the CPU is in
+ * a quiescent state, so count it.
+ *
+ * No memory barrier is required here because both
+ * rcu_qsctr_inc() and rcu_bh_qsctr_inc() reference
+ * only CPU-local variables that other CPUs neither
+ * access nor modify, at least not while the corresponding
+ * CPU is online.
+ */
+
+ rcu_qsctr_inc(cpu);
+ rcu_bh_qsctr_inc(cpu);
+
+ } else if (!in_softirq()) {
+
+ /*
+ * Get here if this CPU did not take its interrupt from
+ * softirq, in other words, if it is not interrupting
+ * a rcu_bh read-side critical section. This is an _bh
+ * critical section, so count it.
+ */
+
+ rcu_bh_qsctr_inc(cpu);
+ }
+ raise_softirq(RCU_SOFTIRQ);
+}
+
+#ifdef CONFIG_SMP
+
+/*
+ * Scan the leaf rcu_node structures, processing dyntick state for any that
+ * have not yet encountered a quiescent state, using the function specified.
+ * Returns 1 if the current grace period ends while scanning (possibly
+ * because we made it end).
+ */
+static int rcu_process_dyntick(struct rcu_state *rsp, long lastcomp,
+ int (*f)(struct rcu_data *))
+{
+ unsigned long bit;
+ int cpu;
+ unsigned long flags;
+ unsigned long mask;
+ struct rcu_node *rnp_cur = rsp->level[NUM_RCU_LVLS - 1];
+ struct rcu_node *rnp_end = &rsp->node[NUM_RCU_NODES];
+
+ for (; rnp_cur < rnp_end; rnp_cur++) {
+ mask = 0;
+ spin_lock_irqsave(&rnp_cur->lock, flags);
+ if (rsp->completed != lastcomp) {
+ spin_unlock_irqrestore(&rnp_cur->lock, flags);
+ return 1;
+ }
+ if (rnp_cur->qsmask == 0) {
+ spin_unlock_irqrestore(&rnp_cur->lock, flags);
+ continue;
+ }
+ cpu = rnp_cur->grplo;
+ bit = 1;
+ for (; cpu <= rnp_cur->grphi; cpu++, bit <<= 1) {
+ if ((rnp_cur->qsmask & bit) != 0 && f(rsp->rda[cpu]))
+ mask |= bit;
+ }
+ if (mask != 0 && rsp->completed == lastcomp) {
+
+ /* cpu_quiet_msk() releases rnp_cur->lock. */
+ cpu_quiet_msk(mask, rsp, rnp_cur, flags);
+ continue;
+ }
+ spin_unlock_irqrestore(&rnp_cur->lock, flags);
+ }
+ return 0;
+}
+
+/*
+ * Force quiescent states on reluctant CPUs, and also detect which
+ * CPUs are in dyntick-idle mode.
+ */
+static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
+{
+ unsigned long flags;
+ long lastcomp;
+ struct rcu_node *rnp = rcu_get_root(rsp);
+ u8 signaled;
+
+ if (ACCESS_ONCE(rsp->completed) == ACCESS_ONCE(rsp->gpnum))
+ return; /* No grace period in progress, nothing to force. */
+ if (!spin_trylock_irqsave(&rsp->fqslock, flags)) {
+ rsp->n_force_qs_lh++; /* Inexact, can lose counts. Tough! */
+ return; /* Someone else is already on the job. */
+ }
+ if (relaxed &&
+ (long)(rsp->jiffies_force_qs - jiffies) >= 0)
+ goto unlock_ret; /* no emergency and done recently. */
+ rsp->n_force_qs++;
+ spin_lock(&rnp->lock);
+ lastcomp = rsp->completed;
+ signaled = rsp->signaled;
+ rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS;
+ if (lastcomp == rsp->gpnum) {
+ rsp->n_force_qs_ngp++;
+ spin_unlock(&rnp->lock);
+ goto unlock_ret; /* no GP in progress, time updated. */
+ }
+ spin_unlock(&rnp->lock);
+ switch (signaled) {
+ case RCU_GP_INIT:
+
+ break; /* grace period still initializing, ignore. */
+
+ case RCU_SAVE_DYNTICK:
+
+ if (RCU_SIGNAL_INIT != RCU_SAVE_DYNTICK)
+ break; /* So gcc recognizes the dead code. */
+
+ /* Record dyntick-idle state. */
+ if (rcu_process_dyntick(rsp, lastcomp,
+ dyntick_save_progress_counter))
+ goto unlock_ret;
+
+ /* Update state, record completion counter. */
+ spin_lock(&rnp->lock);
+ if (lastcomp == rsp->completed) {
+ rsp->signaled = RCU_FORCE_QS;
+ dyntick_record_completed(rsp, lastcomp);
+ }
+ spin_unlock(&rnp->lock);
+ break;
+
+ case RCU_FORCE_QS:
+
+ /* Check dyntick-idle state, send IPI to laggarts. */
+ if (rcu_process_dyntick(rsp, dyntick_recall_completed(rsp),
+ rcu_implicit_dynticks_qs))
+ goto unlock_ret;
+
+ /* Leave state in case more forcing is required. */
+
+ break;
+ }
+unlock_ret:
+ spin_unlock_irqrestore(&rsp->fqslock, flags);
+}
+
+#else /* #ifdef CONFIG_SMP */
+
+static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
+{
+ set_need_resched();
+}
+
+#endif /* #else #ifdef CONFIG_SMP */
+
+/*
+ * This does the RCU processing work from softirq context for the
+ * specified rcu_state and rcu_data structures. This may be called
+ * only from the CPU to whom the rdp belongs.
+ */
+static void
+__rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
+{
+ unsigned long flags;
+
+ /*
+ * If an RCU GP has gone long enough, go check for dyntick
+ * idle CPUs and, if needed, send resched IPIs.
+ */
+ if ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0)
+ force_quiescent_state(rsp, 1);
+
+ /*
+ * Advance callbacks in response to end of earlier grace
+ * period that some other CPU ended.
+ */
+ rcu_process_gp_end(rsp, rdp);
+
+ /* Update RCU state based on any recent quiescent states. */
+ rcu_check_quiescent_state(rsp, rdp);
+
+ /* Does this CPU require a not-yet-started grace period? */
+ if (cpu_needs_another_gp(rsp, rdp)) {
+ spin_lock_irqsave(&rcu_get_root(rsp)->lock, flags);
+ rcu_start_gp(rsp, flags); /* releases above lock */
+ }
+
+ /* If there are callbacks ready, invoke them. */
+ rcu_do_batch(rdp);
+}
+
+/*
+ * Do softirq processing for the current CPU.
+ */
+static void rcu_process_callbacks(struct softirq_action *unused)
+{
+ /*
+ * Memory references from any prior RCU read-side critical sections
+ * executed by the interrupted code must be seen before any RCU
+ * grace-period manipulations below.
+ */
+ smp_mb(); /* See above block comment. */
+
+ __rcu_process_callbacks(&rcu_state, &__get_cpu_var(rcu_data));
+ __rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data));
+
+ /*
+ * Memory references from any later RCU read-side critical sections
+ * executed by the interrupted code must be seen after any RCU
+ * grace-period manipulations above.
+ */
+ smp_mb(); /* See above block comment. */
+}
+
+static void
+__call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
+ struct rcu_state *rsp)
+{
+ unsigned long flags;
+ struct rcu_data *rdp;
+
+ head->func = func;
+ head->next = NULL;
+
+ smp_mb(); /* Ensure RCU update seen before callback registry. */
+
+ /*
+ * Opportunistically note grace-period endings and beginnings.
+ * Note that we might see a beginning right after we see an
+ * end, but never vice versa, since this CPU has to pass through
+ * a quiescent state betweentimes.
+ */
+ local_irq_save(flags);
+ rdp = rsp->rda[smp_processor_id()];
+ rcu_process_gp_end(rsp, rdp);
+ check_for_new_grace_period(rsp, rdp);
+
+ /* Add the callback to our list. */
+ *rdp->nxttail[RCU_NEXT_TAIL] = head;
+ rdp->nxttail[RCU_NEXT_TAIL] = &head->next;
+
+ /* Start a new grace period if one not already started. */
+ if (ACCESS_ONCE(rsp->completed) == ACCESS_ONCE(rsp->gpnum)) {
+ unsigned long nestflag;
+ struct rcu_node *rnp_root = rcu_get_root(rsp);
+
+ spin_lock_irqsave(&rnp_root->lock, nestflag);
+ rcu_start_gp(rsp, nestflag); /* releases rnp_root->lock. */
+ }
+
+ /* Force the grace period if too many callbacks or too long waiting. */
+ if (unlikely(++rdp->qlen > qhimark)) {
+ rdp->blimit = LONG_MAX;
+ force_quiescent_state(rsp, 0);
+ } else if ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0)
+ force_quiescent_state(rsp, 1);
+ local_irq_restore(flags);
+}
+
+/*
+ * Queue an RCU callback for invocation after a grace period.
+ */
+void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
+{
+ __call_rcu(head, func, &rcu_state);
+}
+EXPORT_SYMBOL_GPL(call_rcu);
+
+/*
+ * Queue an RCU for invocation after a quicker grace period.
+ */
+void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
+{
+ __call_rcu(head, func, &rcu_bh_state);
+}
+EXPORT_SYMBOL_GPL(call_rcu_bh);
+
+/*
+ * Check to see if there is any immediate RCU-related work to be done
+ * by the current CPU, for the specified type of RCU, returning 1 if so.
+ * The checks are in order of increasing expense: checks that can be
+ * carried out against CPU-local state are performed first. However,
+ * we must check for CPU stalls first, else we might not get a chance.
+ */
+static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
+{
+ rdp->n_rcu_pending++;
+
+ /* Check for CPU stalls, if enabled. */
+ check_cpu_stall(rsp, rdp);
+
+ /* Is the RCU core waiting for a quiescent state from this CPU? */
+ if (rdp->qs_pending) {
+ rdp->n_rp_qs_pending++;
+ return 1;
+ }
+
+ /* Does this CPU have callbacks ready to invoke? */
+ if (cpu_has_callbacks_ready_to_invoke(rdp)) {
+ rdp->n_rp_cb_ready++;
+ return 1;
+ }
+
+ /* Has RCU gone idle with this CPU needing another grace period? */
+ if (cpu_needs_another_gp(rsp, rdp)) {
+ rdp->n_rp_cpu_needs_gp++;
+ return 1;
+ }
+
+ /* Has another RCU grace period completed? */
+ if (ACCESS_ONCE(rsp->completed) != rdp->completed) { /* outside lock */
+ rdp->n_rp_gp_completed++;
+ return 1;
+ }
+
+ /* Has a new RCU grace period started? */
+ if (ACCESS_ONCE(rsp->gpnum) != rdp->gpnum) { /* outside lock */
+ rdp->n_rp_gp_started++;
+ return 1;
+ }
+
+ /* Has an RCU GP gone long enough to send resched IPIs &c? */
+ if (ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum) &&
+ ((long)(ACCESS_ONCE(rsp->jiffies_force_qs) - jiffies) < 0)) {
+ rdp->n_rp_need_fqs++;
+ return 1;
+ }
+
+ /* nothing to do */
+ rdp->n_rp_need_nothing++;
+ return 0;
+}
+
+/*
+ * Check to see if there is any immediate RCU-related work to be done
+ * by the current CPU, returning 1 if so. This function is part of the
+ * RCU implementation; it is -not- an exported member of the RCU API.
+ */
+int rcu_pending(int cpu)
+{
+ return __rcu_pending(&rcu_state, &per_cpu(rcu_data, cpu)) ||
+ __rcu_pending(&rcu_bh_state, &per_cpu(rcu_bh_data, cpu));
+}
+
+/*
+ * Check to see if any future RCU-related work will need to be done
+ * by the current CPU, even if none need be done immediately, returning
+ * 1 if so. This function is part of the RCU implementation; it is -not-
+ * an exported member of the RCU API.
+ */
+int rcu_needs_cpu(int cpu)
+{
+ /* RCU callbacks either ready or pending? */
+ return per_cpu(rcu_data, cpu).nxtlist ||
+ per_cpu(rcu_bh_data, cpu).nxtlist;
+}
+
+/*
+ * Initialize a CPU's per-CPU RCU data. We take this "scorched earth"
+ * approach so that we don't have to worry about how long the CPU has
+ * been gone, or whether it ever was online previously. We do trust the
+ * ->mynode field, as it is constant for a given struct rcu_data and
+ * initialized during early boot.
+ *
+ * Note that only one online or offline event can be happening at a given
+ * time. Note also that we can accept some slop in the rsp->completed
+ * access due to the fact that this CPU cannot possibly have any RCU
+ * callbacks in flight yet.
+ */
+static void __cpuinit
+rcu_init_percpu_data(int cpu, struct rcu_state *rsp)
+{
+ unsigned long flags;
+ int i;
+ long lastcomp;
+ unsigned long mask;
+ struct rcu_data *rdp = rsp->rda[cpu];
+ struct rcu_node *rnp = rcu_get_root(rsp);
+
+ /* Set up local state, ensuring consistent view of global state. */
+ spin_lock_irqsave(&rnp->lock, flags);
+ lastcomp = rsp->completed;
+ rdp->completed = lastcomp;
+ rdp->gpnum = lastcomp;
+ rdp->passed_quiesc = 0; /* We could be racing with new GP, */
+ rdp->qs_pending = 1; /* so set up to respond to current GP. */
+ rdp->beenonline = 1; /* We have now been online. */
+ rdp->passed_quiesc_completed = lastcomp - 1;
+ rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo);
+ rdp->nxtlist = NULL;
+ for (i = 0; i < RCU_NEXT_SIZE; i++)
+ rdp->nxttail[i] = &rdp->nxtlist;
+ rdp->qlen = 0;
+ rdp->blimit = blimit;
+#ifdef CONFIG_NO_HZ
+ rdp->dynticks = &per_cpu(rcu_dynticks, cpu);
+#endif /* #ifdef CONFIG_NO_HZ */
+ rdp->cpu = cpu;
+ spin_unlock(&rnp->lock); /* irqs remain disabled. */
+
+ /*
+ * A new grace period might start here. If so, we won't be part
+ * of it, but that is OK, as we are currently in a quiescent state.
+ */
+
+ /* Exclude any attempts to start a new GP on large systems. */
+ spin_lock(&rsp->onofflock); /* irqs already disabled. */
+
+ /* Add CPU to rcu_node bitmasks. */
+ rnp = rdp->mynode;
+ mask = rdp->grpmask;
+ do {
+ /* Exclude any attempts to start a new GP on small systems. */
+ spin_lock(&rnp->lock); /* irqs already disabled. */
+ rnp->qsmaskinit |= mask;
+ mask = rnp->grpmask;
+ spin_unlock(&rnp->lock); /* irqs already disabled. */
+ rnp = rnp->parent;
+ } while (rnp != NULL && !(rnp->qsmaskinit & mask));
+
+ spin_unlock(&rsp->onofflock); /* irqs remain disabled. */
+
+ /*
+ * A new grace period might start here. If so, we will be part of
+ * it, and its gpnum will be greater than ours, so we will
+ * participate. It is also possible for the gpnum to have been
+ * incremented before this function was called, and the bitmasks
+ * to not be filled out until now, in which case we will also
+ * participate due to our gpnum being behind.
+ */
+
+ /* Since it is coming online, the CPU is in a quiescent state. */
+ cpu_quiet(cpu, rsp, rdp, lastcomp);
+ local_irq_restore(flags);
+}
+
+static void __cpuinit rcu_online_cpu(int cpu)
+{
+ rcu_init_percpu_data(cpu, &rcu_state);
+ rcu_init_percpu_data(cpu, &rcu_bh_state);
+ open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
+}
+
+/*
+ * Handle CPU online/offline notifcation events.
+ */
+static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
+ unsigned long action, void *hcpu)
+{
+ long cpu = (long)hcpu;
+
+ switch (action) {
+ case CPU_UP_PREPARE:
+ case CPU_UP_PREPARE_FROZEN:
+ rcu_online_cpu(cpu);
+ break;
+ case CPU_DEAD:
+ case CPU_DEAD_FROZEN:
+ case CPU_UP_CANCELED:
+ case CPU_UP_CANCELED_FROZEN:
+ rcu_offline_cpu(cpu);
+ break;
+ default:
+ break;
+ }
+ return NOTIFY_OK;
+}
+
+/*
+ * Compute the per-level fanout, either using the exact fanout specified
+ * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT.
+ */
+#ifdef CONFIG_RCU_FANOUT_EXACT
+static void __init rcu_init_levelspread(struct rcu_state *rsp)
+{
+ int i;
+
+ for (i = NUM_RCU_LVLS - 1; i >= 0; i--)
+ rsp->levelspread[i] = CONFIG_RCU_FANOUT;
+}
+#else /* #ifdef CONFIG_RCU_FANOUT_EXACT */
+static void __init rcu_init_levelspread(struct rcu_state *rsp)
+{
+ int ccur;
+ int cprv;
+ int i;
+
+ cprv = NR_CPUS;
+ for (i = NUM_RCU_LVLS - 1; i >= 0; i--) {
+ ccur = rsp->levelcnt[i];
+ rsp->levelspread[i] = (cprv + ccur - 1) / ccur;
+ cprv = ccur;
+ }
+}
+#endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */
+
+/*
+ * Helper function for rcu_init() that initializes one rcu_state structure.
+ */
+static void __init rcu_init_one(struct rcu_state *rsp)
+{
+ int cpustride = 1;
+ int i;
+ int j;
+ struct rcu_node *rnp;
+
+ /* Initialize the level-tracking arrays. */
+
+ for (i = 1; i < NUM_RCU_LVLS; i++)
+ rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1];
+ rcu_init_levelspread(rsp);
+
+ /* Initialize the elements themselves, starting from the leaves. */
+
+ for (i = NUM_RCU_LVLS - 1; i >= 0; i--) {
+ cpustride *= rsp->levelspread[i];
+ rnp = rsp->level[i];
+ for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) {
+ spin_lock_init(&rnp->lock);
+ rnp->qsmask = 0;
+ rnp->qsmaskinit = 0;
+ rnp->grplo = j * cpustride;
+ rnp->grphi = (j + 1) * cpustride - 1;
+ if (rnp->grphi >= NR_CPUS)
+ rnp->grphi = NR_CPUS - 1;
+ if (i == 0) {
+ rnp->grpnum = 0;
+ rnp->grpmask = 0;
+ rnp->parent = NULL;
+ } else {
+ rnp->grpnum = j % rsp->levelspread[i - 1];
+ rnp->grpmask = 1UL << rnp->grpnum;
+ rnp->parent = rsp->level[i - 1] +
+ j / rsp->levelspread[i - 1];
+ }
+ rnp->level = i;
+ }
+ }
+}
+
+/*
+ * Helper macro for __rcu_init(). To be used nowhere else!
+ * Assigns leaf node pointers into each CPU's rcu_data structure.
+ */
+#define RCU_DATA_PTR_INIT(rsp, rcu_data) \
+do { \
+ rnp = (rsp)->level[NUM_RCU_LVLS - 1]; \
+ j = 0; \
+ for_each_possible_cpu(i) { \
+ if (i > rnp[j].grphi) \
+ j++; \
+ per_cpu(rcu_data, i).mynode = &rnp[j]; \
+ (rsp)->rda[i] = &per_cpu(rcu_data, i); \
+ } \
+} while (0)
+
+static struct notifier_block __cpuinitdata rcu_nb = {
+ .notifier_call = rcu_cpu_notify,
+};
+
+void __init __rcu_init(void)
+{
+ int i; /* All used by RCU_DATA_PTR_INIT(). */
+ int j;
+ struct rcu_node *rnp;
+
+ printk(KERN_WARNING "Experimental hierarchical RCU implementation.\n");
+#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
+ printk(KERN_INFO "RCU-based detection of stalled CPUs is enabled.\n");
+#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
+ rcu_init_one(&rcu_state);
+ RCU_DATA_PTR_INIT(&rcu_state, rcu_data);
+ rcu_init_one(&rcu_bh_state);
+ RCU_DATA_PTR_INIT(&rcu_bh_state, rcu_bh_data);
+
+ for_each_online_cpu(i)
+ rcu_cpu_notify(&rcu_nb, CPU_UP_PREPARE, (void *)(long)i);
+ /* Register notifier for non-boot CPUs */
+ register_cpu_notifier(&rcu_nb);
+ printk(KERN_WARNING "Experimental hierarchical RCU init done.\n");
+}
+
+module_param(blimit, int, 0);
+module_param(qhimark, int, 0);
+module_param(qlowmark, int, 0);
diff --git a/kernel/rcutree_trace.c b/kernel/rcutree_trace.c
new file mode 100644
index 0000000..fcda2b7
--- /dev/null
+++ b/kernel/rcutree_trace.c
@@ -0,0 +1,329 @@
+/*
+ * Read-Copy Update tracing for classic implementation
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright IBM Corporation, 2008
+ *
+ * Papers: http://www.rdrop.com/users/paulmck/RCU
+ *
+ * For detailed explanation of Read-Copy Update mechanism see -
+ * Documentation/RCU
+ *
+ */
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/spinlock.h>
+#include <linux/smp.h>
+#include <linux/rcupdate.h>
+#include <linux/interrupt.h>
+#include <linux/sched.h>
+#include <asm/atomic.h>
+#include <linux/bitops.h>
+#include <linux/module.h>
+#include <linux/completion.h>
+#include <linux/moduleparam.h>
+#include <linux/percpu.h>
+#include <linux/notifier.h>
+#include <linux/cpu.h>
+#include <linux/mutex.h>
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
+
+static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp)
+{
+ if (!rdp->beenonline)
+ return;
+ seq_printf(m, "%3d%cc=%ld g=%ld pq=%d pqc=%ld qp=%d",
+ rdp->cpu,
+ cpu_is_offline(rdp->cpu) ? '!' : ' ',
+ rdp->completed, rdp->gpnum,
+ rdp->passed_quiesc, rdp->passed_quiesc_completed,
+ rdp->qs_pending);
+#ifdef CONFIG_NO_HZ
+ seq_printf(m, " dt=%d/%d dn=%d df=%lu",
+ rdp->dynticks->dynticks,
+ rdp->dynticks->dynticks_nesting,
+ rdp->dynticks->dynticks_nmi,
+ rdp->dynticks_fqs);
+#endif /* #ifdef CONFIG_NO_HZ */
+ seq_printf(m, " of=%lu ri=%lu", rdp->offline_fqs, rdp->resched_ipi);
+ seq_printf(m, " ql=%ld b=%ld\n", rdp->qlen, rdp->blimit);
+}
+
+#define PRINT_RCU_DATA(name, func, m) \
+ do { \
+ int _p_r_d_i; \
+ \
+ for_each_possible_cpu(_p_r_d_i) \
+ func(m, &per_cpu(name, _p_r_d_i)); \
+ } while (0)
+
+static int show_rcudata(struct seq_file *m, void *unused)
+{
+ seq_puts(m, "rcu:\n");
+ PRINT_RCU_DATA(rcu_data, print_one_rcu_data, m);
+ seq_puts(m, "rcu_bh:\n");
+ PRINT_RCU_DATA(rcu_bh_data, print_one_rcu_data, m);
+ return 0;
+}
+
+static int rcudata_open(struct inode *inode, struct file *file)
+{
+ return single_open(file, show_rcudata, NULL);
+}
+
+static struct file_operations rcudata_fops = {
+ .owner = THIS_MODULE,
+ .open = rcudata_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = single_release,
+};
+
+static void print_one_rcu_data_csv(struct seq_file *m, struct rcu_data *rdp)
+{
+ if (!rdp->beenonline)
+ return;
+ seq_printf(m, "%d,%s,%ld,%ld,%d,%ld,%d",
+ rdp->cpu,
+ cpu_is_offline(rdp->cpu) ? "\"Y\"" : "\"N\"",
+ rdp->completed, rdp->gpnum,
+ rdp->passed_quiesc, rdp->passed_quiesc_completed,
+ rdp->qs_pending);
+#ifdef CONFIG_NO_HZ
+ seq_printf(m, ",%d,%d,%d,%lu",
+ rdp->dynticks->dynticks,
+ rdp->dynticks->dynticks_nesting,
+ rdp->dynticks->dynticks_nmi,
+ rdp->dynticks_fqs);
+#endif /* #ifdef CONFIG_NO_HZ */
+ seq_printf(m, ",%lu,%lu", rdp->offline_fqs, rdp->resched_ipi);
+ seq_printf(m, ",%ld,%ld\n", rdp->qlen, rdp->blimit);
+}
+
+static int show_rcudata_csv(struct seq_file *m, void *unused)
+{
+ seq_puts(m, "\"CPU\",\"Online?\",\"c\",\"g\",\"pq\",\"pqc\",\"pq\",");
+#ifdef CONFIG_NO_HZ
+ seq_puts(m, "\"dt\",\"dt nesting\",\"dn\",\"df\",");
+#endif /* #ifdef CONFIG_NO_HZ */
+ seq_puts(m, "\"of\",\"ri\",\"ql\",\"b\"\n");
+ seq_puts(m, "\"rcu:\"\n");
+ PRINT_RCU_DATA(rcu_data, print_one_rcu_data_csv, m);
+ seq_puts(m, "\"rcu_bh:\"\n");
+ PRINT_RCU_DATA(rcu_bh_data, print_one_rcu_data_csv, m);
+ return 0;
+}
+
+static int rcudata_csv_open(struct inode *inode, struct file *file)
+{
+ return single_open(file, show_rcudata_csv, NULL);
+}
+
+static struct file_operations rcudata_csv_fops = {
+ .owner = THIS_MODULE,
+ .open = rcudata_csv_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = single_release,
+};
+
+static void print_one_rcu_state(struct seq_file *m, struct rcu_state *rsp)
+{
+ int level = 0;
+ struct rcu_node *rnp;
+
+ seq_printf(m, "c=%ld g=%ld s=%d jfq=%ld j=%x "
+ "nfqs=%lu/nfqsng=%lu(%lu) fqlh=%lu\n",
+ rsp->completed, rsp->gpnum, rsp->signaled,
+ (long)(rsp->jiffies_force_qs - jiffies),
+ (int)(jiffies & 0xffff),
+ rsp->n_force_qs, rsp->n_force_qs_ngp,
+ rsp->n_force_qs - rsp->n_force_qs_ngp,
+ rsp->n_force_qs_lh);
+ for (rnp = &rsp->node[0]; rnp - &rsp->node[0] < NUM_RCU_NODES; rnp++) {
+ if (rnp->level != level) {
+ seq_puts(m, "\n");
+ level = rnp->level;
+ }
+ seq_printf(m, "%lx/%lx %d:%d ^%d ",
+ rnp->qsmask, rnp->qsmaskinit,
+ rnp->grplo, rnp->grphi, rnp->grpnum);
+ }
+ seq_puts(m, "\n");
+}
+
+static int show_rcuhier(struct seq_file *m, void *unused)
+{
+ seq_puts(m, "rcu:\n");
+ print_one_rcu_state(m, &rcu_state);
+ seq_puts(m, "rcu_bh:\n");
+ print_one_rcu_state(m, &rcu_bh_state);
+ return 0;
+}
+
+static int rcuhier_open(struct inode *inode, struct file *file)
+{
+ return single_open(file, show_rcuhier, NULL);
+}
+
+static struct file_operations rcuhier_fops = {
+ .owner = THIS_MODULE,
+ .open = rcuhier_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = single_release,
+};
+
+static int show_rcugp(struct seq_file *m, void *unused)
+{
+ seq_printf(m, "rcu: completed=%ld gpnum=%ld\n",
+ rcu_state.completed, rcu_state.gpnum);
+ seq_printf(m, "rcu_bh: completed=%ld gpnum=%ld\n",
+ rcu_bh_state.completed, rcu_bh_state.gpnum);
+ return 0;
+}
+
+static int rcugp_open(struct inode *inode, struct file *file)
+{
+ return single_open(file, show_rcugp, NULL);
+}
+
+static struct file_operations rcugp_fops = {
+ .owner = THIS_MODULE,
+ .open = rcugp_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = single_release,
+};
+
+static void print_one_rcu_pending(struct seq_file *m, struct rcu_data *rdp)
+{
+ seq_printf(m, "%3d%cnp=%ld "
+ "qsp=%ld cbr=%ld cng=%ld gpc=%ld gps=%ld nf=%ld nn=%ld\n",
+ rdp->cpu,
+ cpu_is_offline(rdp->cpu) ? '!' : ' ',
+ rdp->n_rcu_pending,
+ rdp->n_rp_qs_pending,
+ rdp->n_rp_cb_ready,
+ rdp->n_rp_cpu_needs_gp,
+ rdp->n_rp_gp_completed,
+ rdp->n_rp_gp_started,
+ rdp->n_rp_need_fqs,
+ rdp->n_rp_need_nothing);
+}
+
+static void print_rcu_pendings(struct seq_file *m, struct rcu_state *rsp)
+{
+ int cpu;
+ struct rcu_data *rdp;
+
+ for_each_possible_cpu(cpu) {
+ rdp = rsp->rda[cpu];
+ if (rdp->beenonline)
+ print_one_rcu_pending(m, rdp);
+ }
+}
+
+static int show_rcu_pending(struct seq_file *m, void *unused)
+{
+ seq_puts(m, "rcu:\n");
+ print_rcu_pendings(m, &rcu_state);
+ seq_puts(m, "rcu_bh:\n");
+ print_rcu_pendings(m, &rcu_bh_state);
+ return 0;
+}
+
+static int rcu_pending_open(struct inode *inode, struct file *file)
+{
+ return single_open(file, show_rcu_pending, NULL);
+}
+
+static struct file_operations rcu_pending_fops = {
+ .owner = THIS_MODULE,
+ .open = rcu_pending_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = single_release,
+};
+
+static struct dentry *rcudir;
+static struct dentry *datadir;
+static struct dentry *datadir_csv;
+static struct dentry *gpdir;
+static struct dentry *hierdir;
+static struct dentry *rcu_pendingdir;
+
+static int __init rcuclassic_trace_init(void)
+{
+ rcudir = debugfs_create_dir("rcu", NULL);
+ if (!rcudir)
+ goto out;
+
+ datadir = debugfs_create_file("rcudata", 0444, rcudir,
+ NULL, &rcudata_fops);
+ if (!datadir)
+ goto free_out;
+
+ datadir_csv = debugfs_create_file("rcudata.csv", 0444, rcudir,
+ NULL, &rcudata_csv_fops);
+ if (!datadir_csv)
+ goto free_out;
+
+ gpdir = debugfs_create_file("rcugp", 0444, rcudir, NULL, &rcugp_fops);
+ if (!gpdir)
+ goto free_out;
+
+ hierdir = debugfs_create_file("rcuhier", 0444, rcudir,
+ NULL, &rcuhier_fops);
+ if (!hierdir)
+ goto free_out;
+
+ rcu_pendingdir = debugfs_create_file("rcu_pending", 0444, rcudir,
+ NULL, &rcu_pending_fops);
+ if (!rcu_pendingdir)
+ goto free_out;
+ return 0;
+free_out:
+ if (datadir)
+ debugfs_remove(datadir);
+ if (datadir_csv)
+ debugfs_remove(datadir_csv);
+ if (gpdir)
+ debugfs_remove(gpdir);
+ debugfs_remove(rcudir);
+out:
+ return 1;
+}
+
+static void __exit rcuclassic_trace_cleanup(void)
+{
+ debugfs_remove(datadir);
+ debugfs_remove(datadir_csv);
+ debugfs_remove(gpdir);
+ debugfs_remove(hierdir);
+ debugfs_remove(rcu_pendingdir);
+ debugfs_remove(rcudir);
+}
+
+
+module_init(rcuclassic_trace_init);
+module_exit(rcuclassic_trace_cleanup);
+
+MODULE_AUTHOR("Paul E. McKenney");
+MODULE_DESCRIPTION("Read-Copy Update tracing for hierarchical implementation");
+MODULE_LICENSE("GPL");
diff --git a/kernel/softirq.c b/kernel/softirq.c
index c506f26..ff5db2e 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -256,6 +256,7 @@ void irq_enter(void)
{
#ifdef CONFIG_NO_HZ
int cpu = smp_processor_id();
+ rcu_irq_enter();
if (idle_cpu(cpu) && !in_interrupt())
tick_nohz_stop_idle(cpu);
#endif
@@ -285,9 +286,9 @@ void irq_exit(void)
#ifdef CONFIG_NO_HZ
/* Make sure that timer wheel updates are propagated */
- if (!in_interrupt() && idle_cpu(smp_processor_id()) && !need_resched())
- tick_nohz_stop_sched_tick(0);
rcu_irq_exit();
+ if (idle_cpu(smp_processor_id()) && !in_interrupt() && !need_resched())
+ tick_nohz_stop_sched_tick(0);
#endif
preempt_enable_no_resched();
}
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 0b50481..1687d6d 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -597,6 +597,19 @@ config RCU_TORTURE_TEST_RUNNABLE
Say N here if you want the RCU torture tests to start only
after being manually enabled via /proc.
+config RCU_CPU_STALL_DETECTOR
+ bool "Check for stalled CPUs delaying RCU grace periods"
+ depends on CLASSIC_RCU || TREE_RCU
+ default n
+ help
+ This option causes RCU to printk information on which
+ CPUs are delaying the current grace period, but only when
+ the grace period extends for excessive time periods.
+
+ Say Y if you want RCU to perform such checks.
+
+ Say N if you are unsure.
+
config KPROBES_SANITY_TEST
bool "Kprobes sanity tests"
depends on DEBUG_KERNEL
--
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