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Subject[PATCH tip/core/rcu 3/4] srcu: Fix process_srcu()/srcu_batches_completed() datarace
Date
From: "Paul E. McKenney" <paulmck@kernel.org>

The srcu_struct structure's ->srcu_idx field is accessed locklessly,
so reads must use READ_ONCE(). This commit therefore adds the needed
READ_ONCE() invocation where it was missed.

This data race was reported by KCSAN. Not appropriate for backporting
due to failure being unlikely.

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

diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 79848f7d..119a373 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -1079,7 +1079,7 @@ EXPORT_SYMBOL_GPL(srcu_barrier);
*/
unsigned long srcu_batches_completed(struct srcu_struct *ssp)
{
- return ssp->srcu_idx;
+ return READ_ONCE(ssp->srcu_idx);
}
EXPORT_SYMBOL_GPL(srcu_batches_completed);

--
2.9.5
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