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Date: Wed, 3 Mar 2010 07:46:57 -0800
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: linux-kernel@...r.kernel.org
Cc: mingo@...e.hu, laijs@...fujitsu.com, dipankar@...ibm.com,
akpm@...ux-foundation.org, mathieu.desnoyers@...ymtl.ca,
josh@...htriplett.org, dvhltc@...ibm.com, niv@...ibm.com,
tglx@...utronix.de, peterz@...radead.org, rostedt@...dmis.org,
Valdis.Kletnieks@...edu, dhowells@...hat.com,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 2/4] rcu: suppress RCU lockdep warnings during early boot
RCU is used during very early boot, before RCU and lockdep have been
initialized. So make the underlying primitives (rcu_read_lock_held(),
rcu_read_lock_bh_held(), rcu_read_lock_sched_held(), and
rcu_dereference_check()) check for early boot via the rcu_scheduler_active
flag. This will suppress false positives.
Also introduce a debug_lockdep_rcu_enabled() static inline helper
function, which tags the CONTINUE_PROVE_RCU case as likely(), as suggested
by Ingo Molnar.
Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
include/linux/rcupdate.h | 35 ++++++++++++++++++++++++++---------
lib/locking-selftest.c | 5 +++++
2 files changed, 31 insertions(+), 9 deletions(-)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index c843736..fb80ce3 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -97,6 +97,11 @@ extern struct lockdep_map rcu_sched_lock_map;
# define rcu_read_release_sched() \
lock_release(&rcu_sched_lock_map, 1, _THIS_IP_)
+static inline int debug_lockdep_rcu_enabled(void)
+{
+ return likely(rcu_scheduler_active && debug_locks);
+}
+
/**
* rcu_read_lock_held - might we be in RCU read-side critical section?
*
@@ -104,12 +109,14 @@ extern struct lockdep_map rcu_sched_lock_map;
* an RCU read-side critical section. In absence of CONFIG_PROVE_LOCKING,
* this assumes we are in an RCU read-side critical section unless it can
* prove otherwise.
+ *
+ * Check rcu_scheduler_active to prevent false positives during boot.
*/
static inline int rcu_read_lock_held(void)
{
- if (debug_locks)
- return lock_is_held(&rcu_lock_map);
- return 1;
+ if (!debug_lockdep_rcu_enabled())
+ return 1;
+ return lock_is_held(&rcu_lock_map);
}
/**
@@ -119,12 +126,14 @@ static inline int rcu_read_lock_held(void)
* an RCU-bh read-side critical section. In absence of CONFIG_PROVE_LOCKING,
* this assumes we are in an RCU-bh read-side critical section unless it can
* prove otherwise.
+ *
+ * Check rcu_scheduler_active to prevent false positives during boot.
*/
static inline int rcu_read_lock_bh_held(void)
{
- if (debug_locks)
- return lock_is_held(&rcu_bh_lock_map);
- return 1;
+ if (!debug_lockdep_rcu_enabled())
+ return 1;
+ return lock_is_held(&rcu_bh_lock_map);
}
/**
@@ -135,14 +144,18 @@ static inline int rcu_read_lock_bh_held(void)
* this assumes we are in an RCU-sched read-side critical section unless it
* can prove otherwise. Note that disabling of preemption (including
* disabling irqs) counts as an RCU-sched read-side critical section.
+ *
+ * Check rcu_scheduler_active to prevent false positives during boot.
*/
static inline int rcu_read_lock_sched_held(void)
{
int lockdep_opinion = 0;
+ if (!debug_lockdep_rcu_enabled())
+ return 1;
if (debug_locks)
lockdep_opinion = lock_is_held(&rcu_sched_lock_map);
- return lockdep_opinion || preempt_count() != 0 || !rcu_scheduler_active;
+ return lockdep_opinion || preempt_count() != 0;
}
#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
@@ -154,6 +167,10 @@ static inline int rcu_read_lock_sched_held(void)
# define rcu_read_acquire_sched() do { } while (0)
# define rcu_read_release_sched() do { } while (0)
+static inline void debug_lockdep_rcu_update(void)
+{
+}
+
static inline int rcu_read_lock_held(void)
{
return 1;
@@ -166,7 +183,7 @@ static inline int rcu_read_lock_bh_held(void)
static inline int rcu_read_lock_sched_held(void)
{
- return preempt_count() != 0 || !rcu_scheduler_active;
+ return !rcu_scheduler_active || preempt_count() != 0;
}
#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
@@ -184,7 +201,7 @@ static inline int rcu_read_lock_sched_held(void)
*/
#define rcu_dereference_check(p, c) \
({ \
- if (debug_locks && !(c)) \
+ if (debug_lockdep_rcu_enabled() && !(c)) \
lockdep_rcu_dereference(__FILE__, __LINE__); \
rcu_dereference_raw(p); \
})
diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c
index 619313e..5c549b8 100644
--- a/lib/locking-selftest.c
+++ b/lib/locking-selftest.c
@@ -21,6 +21,7 @@
#include <linux/interrupt.h>
#include <linux/debug_locks.h>
#include <linux/irqflags.h>
+#include <linux/rcupdate.h>
/*
* Change this to 1 if you want to see the failure printouts:
@@ -1192,6 +1193,7 @@ void locking_selftest(void)
if (unexpected_testcase_failures) {
printk("-----------------------------------------------------------------\n");
debug_locks = 0;
+ debug_lockdep_rcu_update();
printk("BUG: %3d unexpected failures (out of %3d) - debugging disabled! |\n",
unexpected_testcase_failures, testcase_total);
printk("-----------------------------------------------------------------\n");
@@ -1201,18 +1203,21 @@ void locking_selftest(void)
expected_testcase_failures, testcase_total);
printk("----------------------------------------------------\n");
debug_locks = 1;
+ debug_lockdep_rcu_update();
} else if (expected_testcase_failures && !testcase_successes) {
printk("--------------------------------------------------------\n");
printk("All %3d testcases failed, as expected. |\n",
expected_testcase_failures);
printk("----------------------------------------\n");
debug_locks = 1;
+ debug_lockdep_rcu_update();
} else {
printk("-------------------------------------------------------\n");
printk("Good, all %3d testcases passed! |\n",
testcase_successes);
printk("---------------------------------\n");
debug_locks = 1;
+ debug_lockdep_rcu_update();
}
debug_locks_silent = 0;
}
--
1.6.6
--
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