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Subject[PATCH rcu 6/9] rcu: Mark writes to the rcu_segcblist structure's ->flags field
Date
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>
---
kernel/rcu/rcu_segcblist.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/rcu/rcu_segcblist.h b/kernel/rcu/rcu_segcblist.h
index e373fbe44da5e..431cee212467d 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,
--
2.31.1.189.g2e36527f23
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