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Date: Wed, 14 Dec 2011 18:47:38 +0100 From: Frederic Weisbecker <fweisbec@...il.com> To: Ingo Molnar <mingo@...e.hu> Cc: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>, Suresh Siddha <suresh.b.siddha@...el.com>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, tglx@...utronix.de, josh@...htriplett.org, keescook@...omium.org, linux-kernel@...r.kernel.org Subject: Re: [GIT PULL rcu/next] RCU commits for 3.3 On Wed, Dec 14, 2011 at 05:30:11PM +0100, Frederic Weisbecker wrote: > On Wed, Dec 14, 2011 at 04:47:36PM +0100, Ingo Molnar wrote: > > > > * Paul E. McKenney <paulmck@...ux.vnet.ibm.com> wrote: > > > > > Hello, Ingo, > > > > > > The major features of this series are RCU infrastructure in > > > support of Frederic Weisbecker's tickless userspace work and a > > > reworked RCU_FAST_NO_HZ that improves energy efficiency on > > > large lightly loaded SMP systems by allowing the > > > scheduler-clock tick to be turned off more quickly upon entry > > > to idle, even when RCU callbacks are queued on the newly idle > > > CPU. In addition, RCU_FAST_NO_HZ may now be used on systems > > > running TREE_PREEMPT_RCU, where earlier it was restricted to > > > TREE_RCU. > > > > > > In addition, this series provides additional event tracing, > > > rcutorture changes that improve automated KVM-based testing of > > > RCU, introduces an srcu_read_lock_raw() needed by uprobes, and > > > ports a couple of patches from -rt to mainline. Finally, this > > > series updates documentation, improves diagnostics, and fixes > > > a number of bugs, including a nasty use of RCU from the idle > > > task spotted and fixed by Frederic Weisbecker. > > > > > > These commits have been posted to LKML and updated based on > > > feedback: > > > > > > https://lkml.org/lkml/2011/11/2/363 > > > https://lkml.org/lkml/2011/11/15/302 > > > https://lkml.org/lkml/2011/11/28/588 > > > https://lkml.org/lkml/2011/12/3/77 > > > https://lkml.org/lkml/2011/12/12/625 > > > > > > They have also been exposed to -next testing. > > > > > > These changes are based off of 3.2-rc5 and are available at > > > the git repository at: > > > > > > git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git rcu/next > > > > > > Could you please pull them into -tip for additional testing? > > > > > > Thanx, Paul > > > > > > ------------------> > > > Frederic Weisbecker (11): > > > rcu: Detect illegal rcu dereference in extended quiescent state > > > rcu: Inform the user about extended quiescent state on PROVE_RCU warning > > > rcu: Warn when rcu_read_lock() is used in extended quiescent state > > > nohz: Separate out irq exit and idle loop dyntick logic > > > nohz: Allow rcu extended quiescent state handling seperately from tick stop > > > x86: Enter rcu extended qs after idle notifier call > > > x86: Call idle notifier after irq_enter() > > > rcu: Fix early call to rcu_idle_enter() > > > nohz: Remove tick_nohz_idle_enter_norcu() / tick_nohz_idle_exit_norcu() > > > rcu: Don't check irq nesting from rcu idle entry/exit > > > rcu: Irq nesting is always 0 on rcu_enter_idle_common > > > > > > Josh Triplett (1): > > > driver-core/cpu: Expose hotpluggability to the rest of the kernel > > > > > > Kees Cook (1): > > > docs: Additional LWN links to RCU API > > > > > > Paul E. McKenney (49): > > > rcu: ->signaled better named ->fqs_state > > > rcu: Avoid RCU-preempt expedited grace-period botch > > > rcu: Make synchronize_sched_expedited() better at work sharing > > > lockdep: Update documentation for lock-class leak detection > > > rcu: Track idleness independent of idle tasks > > > trace: Allow ftrace_dump() to be called from modules > > > rcu: Add failure tracing to rcutorture > > > rcu: Document failing tick as cause of RCU CPU stall warning > > > rcu: Disable preemption in rcu_is_cpu_idle() > > > rcu: Remove one layer of abstraction from PROVE_RCU checking > > > rcu: Warn when srcu_read_lock() is used in an extended quiescent state > > > rcu: Make srcu_read_lock_held() call common lockdep-enabled function > > > powerpc: Tell RCU about idle after hcall tracing > > > rcu: Introduce raw SRCU read-side primitives > > > rcu: Add documentation for raw SRCU read-side primitives > > > rcu: Deconfuse dynticks entry-exit tracing > > > rcu: Add more information to the wrong-idle-task complaint > > > rcu: Allow dyntick-idle mode for CPUs with callbacks > > > rcu: Fix idle-task checks > > > rcu: Permit RCU_FAST_NO_HZ to be used by TREE_PREEMPT_RCU > > > rcu: Add rcutorture system-shutdown capability > > > rcu: Control rcutorture startup from kernel boot parameters > > > sched: Add is_idle_task() to handle invalidated uses of idle_cpu() > > > rcu: Make RCU use the new is_idle_task() API > > > sparc: Make SPARC use the new is_idle_task() API > > > kdb: Make KDB use the new is_idle_task() API > > > events: Make events use the new is_idle_task() API > > > tile: Make tile use the new is_idle_task() API > > > rcu: Add rcutorture CPU-hotplug capability > > > doc: Add load/store guarantees to Documentation/atomic-ops.txt > > > rcu: Update trace_rcu_dyntick() header comment > > > rcu: Add tracing for RCU_FAST_NO_HZ > > > rcu: Go dyntick-idle more quickly if CPU has serviced current grace period > > > rcu: Avoid needlessly IPIing CPUs at GP end > > > rcu: Eliminate RCU_FAST_NO_HZ grace-period hang > > > rcu: Reduce latency of rcu_prepare_for_idle() > > > rcu: Remove dynticks false positives and RCU failures > > > rcu: Identify dyntick-idle CPUs on first force_quiescent_state() pass > > > rcu: Document same-context read-side constraints > > > rcu: Permit dyntick-idle with callbacks pending > > > rcu: Keep invoking callbacks if CPU otherwise idle > > > rcu: Adaptive dyntick-idle preparation > > > rcu: Remove redundant rcu_cpu_stall_suppress declaration > > > rcu: Make rcutorture test for hotpluggability before offlining CPUs > > > rcu: Add rcutorture tests for srcu_read_lock_raw() > > > rcu: Augment rcu_batch_end tracing for idle and callback state > > > Revert "rcu: Permit rt_mutex_unlock() with irqs disabled" > > > rcu: Apply ACCESS_ONCE() to rcu_boost() return value > > > cpu: Export cpu_up() > > > > > > Thomas Gleixner (2): > > > rcu: Omit self-awaken when setting up expedited grace period > > > rcu: Remove redundant return from rcu_report_exp_rnp() > > > > > > Documentation/RCU/checklist.txt | 6 + > > > Documentation/RCU/rcu.txt | 10 +- > > > Documentation/RCU/stallwarn.txt | 16 +- > > > Documentation/RCU/torture.txt | 13 ++ > > > Documentation/RCU/trace.txt | 4 - > > > Documentation/RCU/whatisRCU.txt | 19 ++- > > > Documentation/atomic_ops.txt | 87 +++++++++ > > > Documentation/lockdep-design.txt | 63 +++++++ > > > arch/arm/kernel/process.c | 6 +- > > > arch/avr32/kernel/process.c | 6 +- > > > arch/blackfin/kernel/process.c | 6 +- > > > arch/microblaze/kernel/process.c | 6 +- > > > arch/mips/kernel/process.c | 6 +- > > > arch/openrisc/kernel/idle.c | 6 +- > > > arch/powerpc/kernel/idle.c | 15 ++- > > > arch/powerpc/platforms/iseries/setup.c | 12 +- > > > arch/powerpc/platforms/pseries/lpar.c | 4 + > > > arch/s390/kernel/process.c | 6 +- > > > arch/sh/kernel/idle.c | 6 +- > > > arch/sparc/kernel/process_64.c | 6 +- > > > arch/sparc/kernel/setup_32.c | 2 +- > > > arch/tile/kernel/process.c | 6 +- > > > arch/tile/mm/fault.c | 4 +- > > > arch/um/kernel/process.c | 6 +- > > > arch/unicore32/kernel/process.c | 6 +- > > > arch/x86/kernel/apic/apic.c | 6 +- > > > arch/x86/kernel/apic/io_apic.c | 2 +- > > > arch/x86/kernel/cpu/mcheck/therm_throt.c | 2 +- > > > arch/x86/kernel/cpu/mcheck/threshold.c | 2 +- > > > arch/x86/kernel/irq.c | 6 +- > > > arch/x86/kernel/process_32.c | 6 +- > > > arch/x86/kernel/process_64.c | 10 +- > > > drivers/base/cpu.c | 7 + > > > include/linux/cpu.h | 1 + > > > include/linux/hardirq.h | 21 --- > > > include/linux/rcupdate.h | 115 ++++++++----- > > > include/linux/sched.h | 8 + > > > include/linux/srcu.h | 87 ++++++++-- > > > include/linux/tick.h | 11 +- > > > include/trace/events/rcu.h | 122 +++++++++++-- > > > init/Kconfig | 10 +- > > > kernel/cpu.c | 1 + > > > kernel/debug/kdb/kdb_support.c | 2 +- > > > kernel/events/core.c | 2 +- > > > kernel/lockdep.c | 22 +++ > > > kernel/rcu.h | 7 + > > > kernel/rcupdate.c | 12 ++ > > > kernel/rcutiny.c | 149 +++++++++++++-- > > > kernel/rcutiny_plugin.h | 29 +++- > > > kernel/rcutorture.c | 225 ++++++++++++++++++++++- > > > kernel/rcutree.c | 290 +++++++++++++++++++++--------- > > > kernel/rcutree.h | 26 ++-- > > > kernel/rcutree_plugin.h | 289 ++++++++++++++++++++++++------ > > > kernel/rcutree_trace.c | 12 +- > > > kernel/rtmutex.c | 8 - > > > kernel/softirq.c | 4 +- > > > kernel/time/tick-sched.c | 97 ++++++---- > > > kernel/trace/trace.c | 1 + > > > 58 files changed, 1512 insertions(+), 407 deletions(-) > > > > Pulled into tip:core/rcu, thanks a lot Paul! > > > > Note that this commit from Frederic: > > > > 69e1e811dcc4: sched, nohz: Track nr_busy_cpus in the sched_group_power > > > > conflicted with this commit from Suresh in sched/core: > > > > 69e1e811dcc4: sched, nohz: Track nr_busy_cpus in the sched_group_power > > > > I resolved it by making the set_cpu_sd_state_idle() call > > unconditional within the newly decoupled > > tick_nohz_stop_sched_tick() function - please double check that > > it's the right resolution. > > After a quick look, I believe this should rather be under tick_nohz_idle_enter(), > (This is the equivalent of the old tick_nohz_stop_sched_tick(1)) > This wants to be set only once we enter idle, not everytime we have an idle > interrupt. I don't know how you plan to fix the conflict, by redoing the merge or by applying a patch on tip/master. In any case, here is a patch you can use. Feel free to apply it as is or to just refer to its diff to redo the merge: (Outrageously only compile tested) --- From: Frederic Weisbecker <fweisbec@...il.com> Date: Wed, 14 Dec 2011 18:36:00 +0100 Subject: [PATCH] sched: Only update the CPU idleness in the domain hierarchy from idle loop entry We don't need to inform the sched domain hierarchy about the CPU idleness everytime we call tick_nohz_stop_sched_tick() as this includes both idle loop entry and idle interrupt exit. Doing it once from the idle loop entry is enough, call set_cpu_sd_state_idle() only from tick_nohz_idle_enter() instead to fix this. Signed-off-by: Frederic Weisbecker <fweisbec@...il.com> Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com> Cc: Suresh Siddha <suresh.b.siddha@...el.com> Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl> --- kernel/time/tick-sched.c | 16 ++++++++-------- 1 files changed, 8 insertions(+), 8 deletions(-) diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 1f6dc515..696c997 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -289,14 +289,6 @@ static void tick_nohz_stop_sched_tick(struct tick_sched *ts) now = tick_nohz_start_idle(cpu, ts); /* - * Update the idle state in the scheduler domain hierarchy - * when tick_nohz_stop_sched_tick() is called from the idle loop. - * State will be updated to busy during the first busy tick after - * exiting idle. - */ - set_cpu_sd_state_idle(); - - /* * If this cpu is offline and it is the one which updates * jiffies, then give up the assignment and let it be taken by * the cpu which runs the tick timer next. If we don't drop @@ -483,6 +475,14 @@ void tick_nohz_idle_enter(void) * update of the idle time accounting in tick_nohz_start_idle(). */ ts->inidle = 1; + + /* + * Update the idle state in the scheduler domain hierarchy + * when tick_nohz_idle_enter() is called from the idle loop. + * State will be updated to busy during the first busy tick after + * exiting idle. + */ + set_cpu_sd_state_idle(); tick_nohz_stop_sched_tick(ts); local_irq_enable(); -- 1.7.5.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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