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[5.17,0840/1126] rcu: Mark writes to the rcu_segcblist structures ->flags field

Message ID 20220405070432.210797778@linuxfoundation.org
State New
Headers show
Series None | expand

Commit Message

Greg Kroah-Hartman April 5, 2022, 7:26 a.m. UTC 
From: Paul E. McKenney <paulmck@kernel.org>

[ Upstream commit c09929031018913b5783872a8b8cdddef4a543c7 ]

KCSAN reports data races between the rcu_segcblist_clear_flags() and
rcu_segcblist_set_flags() functions, though misreporting the latter
as a call to rcu_segcblist_is_enabled() from call_rcu().  This commit
converts the updates of this field to WRITE_ONCE(), relying on the
resulting unmarked reads to continue to detect buggy concurrent writes
to this field.

Reported-by: Zhouyi Zhou <zhouzhouyi@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 kernel/rcu/rcu_segcblist.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
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Patch

diff --git a/kernel/rcu/rcu_segcblist.h b/kernel/rcu/rcu_segcblist.h
index e373fbe44da5..431cee212467 100644
--- a/kernel/rcu/rcu_segcblist.h
+++ b/kernel/rcu/rcu_segcblist.h
@@ -56,13 +56,13 @@  static inline long rcu_segcblist_n_cbs(struct rcu_segcblist *rsclp)
 static inline void rcu_segcblist_set_flags(struct rcu_segcblist *rsclp,
 					   int flags)
 {
-	rsclp->flags |= flags;
+	WRITE_ONCE(rsclp->flags, rsclp->flags | flags);
 }
 
 static inline void rcu_segcblist_clear_flags(struct rcu_segcblist *rsclp,
 					     int flags)
 {
-	rsclp->flags &= ~flags;
+	WRITE_ONCE(rsclp->flags, rsclp->flags & ~flags);
 }
 
 static inline bool rcu_segcblist_test_flags(struct rcu_segcblist *rsclp,