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authorPaul E. McKenney <paul.mckenney@linaro.org>2012-07-02 14:42:01 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2012-09-23 07:42:49 -0700
commite3ebfb96f396731ca2d0b108785d5da31b53ab00 (patch)
tree7bac429c3cad5f00894746270322d5a4119cea47 /lib
parenta10d206ef1a83121ab7430cb196e0376a7145b22 (diff)
downloadop-kernel-dev-e3ebfb96f396731ca2d0b108785d5da31b53ab00.zip
op-kernel-dev-e3ebfb96f396731ca2d0b108785d5da31b53ab00.tar.gz
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 'lib')
-rw-r--r--lib/Kconfig.debug14
1 files changed, 14 insertions, 0 deletions
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 2403a63..dacbbe4 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -629,6 +629,20 @@ config PROVE_RCU_REPEATEDLY
Say N if you are unsure.
+config PROVE_RCU_DELAY
+ bool "RCU debugging: preemptible RCU race provocation"
+ depends on DEBUG_KERNEL && PREEMPT_RCU
+ default n
+ help
+ There is a class of races that involve an unlikely preemption
+ of __rcu_read_unlock() just after ->rcu_read_lock_nesting has
+ been set to INT_MIN. This feature inserts a delay at that
+ point to increase the probability of these races.
+
+ Say Y to increase probability of preemption of __rcu_read_unlock().
+
+ Say N if you are unsure.
+
config SPARSE_RCU_POINTER
bool "RCU debugging: sparse-based checks for pointer usage"
default n
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