[tip/core/rcu,11/30] rcu: Add READ_ONCE() to rcu_segcblist ->tails[]
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Message ID 20200214235607.13749-11-paulmck@kernel.org
State In Next
Commit 3d56b0943d87f5d9afc5a14dfdc50d0288d630ac
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Series
  • Miscellaneous fixes for v5.7
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Commit Message

Paul E. McKenney Feb. 14, 2020, 11:55 p.m. UTC 
From: "Paul E. McKenney" <paulmck@kernel.org>

The rcu_segcblist structure's ->tails[] array entries are read
locklessly, so this commit adds the READ_ONCE() to a load in order to
avoid destructive compiler optimizations.

This data race was reported by KCSAN.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/rcu_segcblist.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Patch
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diff --git a/kernel/rcu/rcu_segcblist.c b/kernel/rcu/rcu_segcblist.c
index 5f4fd3b..426a472 100644
--- a/kernel/rcu/rcu_segcblist.c
+++ b/kernel/rcu/rcu_segcblist.c
@@ -182,7 +182,7 @@  void rcu_segcblist_offload(struct rcu_segcblist *rsclp)
 bool rcu_segcblist_ready_cbs(struct rcu_segcblist *rsclp)
 {
 	return rcu_segcblist_is_enabled(rsclp) &&
-	       &rsclp->head != rsclp->tails[RCU_DONE_TAIL];
+	       &rsclp->head != READ_ONCE(rsclp->tails[RCU_DONE_TAIL]);
 }
 
 /*