The following commit has been merged into the core/rcu branch of tip: Commit-ID: b0c18c87730a4de6da0303fa99aea43e814233f9 Gitweb: https://git.kernel.org/tip/b0c18c87730a4de6da0303fa99aea43e814233f9 Author: Paul E. McKenney <paulmck@xxxxxxxxxx> AuthorDate: Fri, 03 Jan 2020 12:12:06 -08:00 Committer: Paul E. McKenney <paulmck@xxxxxxxxxx> CommitterDate: Thu, 20 Feb 2020 15:58:22 -08:00 rcu: Add WRITE_ONCE to rcu_node ->exp_seq_rq store The rcu_node structure's ->exp_seq_rq field is read locklessly, so this commit adds the WRITE_ONCE() to a load 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_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 d7e0484..85b009e 100644 --- a/kernel/rcu/tree_exp.h +++ b/kernel/rcu/tree_exp.h @@ -314,7 +314,7 @@ static bool exp_funnel_lock(unsigned long s) sync_exp_work_done(s)); return true; } - rnp->exp_seq_rq = s; /* Followers can wait on us. */ + WRITE_ONCE(rnp->exp_seq_rq, s); /* Followers can wait on us. */ spin_unlock(&rnp->exp_lock); trace_rcu_exp_funnel_lock(rcu_state.name, rnp->level, rnp->grplo, rnp->grphi, TPS("nxtlvl"));
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