From e3ebfb96f396731ca2d0b108785d5da31b53ab00 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Mon, 2 Jul 2012 14:42:01 -0700 Subject: 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 Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett --- lib/Kconfig.debug | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'lib') diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 2403a63b5da5..dacbbe4d7a80 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 -- cgit v1.2.3