The following commit has been merged into the core/rcu branch of tip: Commit-ID: 24bb9eccf7ff335c16c2970ac7cd5c32a92821a6 Gitweb: https://git.kernel.org/tip/24bb9eccf7ff335c16c2970ac7cd5c32a92821a6 Author: Paul E. McKenney <paulmck@xxxxxxxxxx> AuthorDate: Sun, 22 Dec 2019 19:55:50 -08:00 Committer: Paul E. McKenney <paulmck@xxxxxxxxxx> CommitterDate: Thu, 20 Feb 2020 15:58:21 -08:00 rcu: Fix exp_funnel_lock()/rcu_exp_wait_wake() datarace The rcu_node structure's ->exp_seq_rq field is accessed locklessly, so updates must use WRITE_ONCE(). This commit therefore adds the needed WRITE_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@xxxxxxxxxx> --- kernel/rcu/tree_exp.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h index dcbd757..d7e0484 100644 --- a/kernel/rcu/tree_exp.h +++ b/kernel/rcu/tree_exp.h @@ -589,7 +589,7 @@ static void rcu_exp_wait_wake(unsigned long s) spin_lock(&rnp->exp_lock); /* Recheck, avoid hang in case someone just arrived. */ if (ULONG_CMP_LT(rnp->exp_seq_rq, s)) - rnp->exp_seq_rq = s; + WRITE_ONCE(rnp->exp_seq_rq, s); spin_unlock(&rnp->exp_lock); } smp_mb(); /* All above changes before wakeup. */
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