rcu: Add PROVE_RCU_DELAY to provoke difficult races
authorPaul E. McKenney <paul.mckenney@linaro.org>
Mon, 2 Jul 2012 21:42:01 +0000 (14:42 -0700)
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Sun, 23 Sep 2012 14:42:49 +0000 (07:42 -0700)
commite3ebfb96f396731ca2d0b108785d5da31b53ab00
tree7bac429c3cad5f00894746270322d5a4119cea47
parenta10d206ef1a83121ab7430cb196e0376a7145b22
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>
kernel/rcupdate.c
lib/Kconfig.debug