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| author | Paul E. McKenney <paul.mckenney@linaro.org> | 2012-07-02 14:42:01 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2012-09-23 07:42:49 -0700 |
| commit | e3ebfb96f396731ca2d0b108785d5da31b53ab00 (patch) | |
| tree | 7bac429c3cad5f00894746270322d5a4119cea47 /kernel/rcupdate.c | |
| parent | a10d206ef1a83121ab7430cb196e0376a7145b22 (diff) | |
| download | linux-e3ebfb96f396731ca2d0b108785d5da31b53ab00.tar.bz2 | |
rcu: Add PROVE_RCU_DELAY to provoke difficult races
There have been some recent bugs that were triggered only when
preemptible RCU's __rcu_read_unlock() was preempted just after setting
->rcu_read_lock_nesting to INT_MIN, which is a low-probability event.
Therefore, reproducing those bugs (to say nothing of gaining confidence
in alleged fixes) was quite difficult. This commit therefore creates
a new debug-only RCU kernel config option that forces a short delay
in __rcu_read_unlock() to increase the probability of those sorts of
bugs occurring.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Diffstat (limited to 'kernel/rcupdate.c')
| -rw-r--r-- | kernel/rcupdate.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c index 4e6a61b15e86..29ca1c6da594 100644 --- a/kernel/rcupdate.c +++ b/kernel/rcupdate.c @@ -45,6 +45,7 @@ #include <linux/mutex.h> #include <linux/export.h> #include <linux/hardirq.h> +#include <linux/delay.h> #define CREATE_TRACE_POINTS #include <trace/events/rcu.h> @@ -81,6 +82,9 @@ void __rcu_read_unlock(void) } else { barrier(); /* critical section before exit code. */ t->rcu_read_lock_nesting = INT_MIN; +#ifdef CONFIG_PROVE_RCU_DELAY + udelay(10); /* Make preemption more probable. */ +#endif /* #ifdef CONFIG_PROVE_RCU_DELAY */ barrier(); /* assign before ->rcu_read_unlock_special load */ if (unlikely(ACCESS_ONCE(t->rcu_read_unlock_special))) rcu_read_unlock_special(t); |