[PATCH tip/core/rcu 17/23] rcu: Add random PROVE_RCU_DELAY to grace-period initialization

[Paul E. McKenney]

From: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>

Preemption greatly raised the probability of certain types of race
conditions, so this commit adds an anti-heisenbug to greatly increase
the collision cross section, also known as the probability of occurrence.

Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
---
 kernel/rcutree.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 25a671c..5cb003d 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -52,6 +52,7 @@
 #include <linux/prefetch.h>
 #include <linux/delay.h>
 #include <linux/stop_machine.h>
+#include <linux/random.h>
 
 #include "rcutree.h"
 #include <trace/events/rcu.h>
@@ -1085,6 +1086,10 @@ static int rcu_gp_init(struct rcu_state *rsp)
 					    rnp->level, rnp->grplo,
 					    rnp->grphi, rnp->qsmask);
 		raw_spin_unlock_irq(&rnp->lock);
+#ifdef CONFIG_PROVE_RCU_DELAY
+		if ((random32() % (rcu_num_nodes * 8)) == 0)
+			schedule_timeout_uninterruptible(2);
+#endif /* #ifdef CONFIG_PROVE_RCU_DELAY */
 		cond_resched();
 	}
 
-- 
1.7.8

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