The following commit has been merged into the core/rcu branch of tip: Commit-ID: 59881bcd85a06565c53fd13ce3b0ad7fa55e560c Gitweb: https://git.kernel.org/tip/59881bcd85a06565c53fd13ce3b0ad7fa55e560c Author: Paul E. McKenney <paulmck@xxxxxxxxxx> AuthorDate: Mon, 20 Jan 2020 15:29:04 -08:00 Committer: Paul E. McKenney <paulmck@xxxxxxxxxx> CommitterDate: Thu, 20 Feb 2020 15:58:23 -08:00 rcu: Add WRITE_ONCE() to rcu_state ->gp_start The rcu_state structure's ->gp_start field is read locklessly, so this commit adds the WRITE_ONCE() to an update in order to provide proper documentation and READ_ONCE()/WRITE_ONCE() pairing. This data race was reported by KCSAN. Not appropriate for backporting due to failure being unlikely. Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx> --- kernel/rcu/tree_stall.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h index bca637b..488b71d 100644 --- a/kernel/rcu/tree_stall.h +++ b/kernel/rcu/tree_stall.h @@ -102,7 +102,7 @@ static void record_gp_stall_check_time(void) unsigned long j = jiffies; unsigned long j1; - rcu_state.gp_start = j; + WRITE_ONCE(rcu_state.gp_start, j); j1 = rcu_jiffies_till_stall_check(); /* Record ->gp_start before ->jiffies_stall. */ smp_store_release(&rcu_state.jiffies_stall, j + j1); /* ^^^ */
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