This is a note to let you know that I've just added the patch titled
rcu: Mark writes to the rcu_segcblist structure's ->flags field
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
rcu-mark-writes-to-the-rcu_segcblist-structure-s-fla.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 46a2ab8e4fd3f7b5d705e0bb0a35eafd297f6e81
Author: Paul E. McKenney <paulmck@xxxxxxxxxx>
Date: Tue Jan 4 10:34:34 2022 -0800
rcu: Mark writes to the rcu_segcblist structure's ->flags field
[ 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@xxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Cc: Frederic Weisbecker <frederic@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/kernel/rcu/rcu_segcblist.h b/kernel/rcu/rcu_segcblist.h
index 9a19328ff251..5d405943823e 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,
