Commit aba9645b authored by Joel Fernandes (Google)'s avatar Joel Fernandes (Google) Committed by Paul E. McKenney
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rcu: Use READ_ONCE() for lockless read of rnp->qsmask 



The rnp->qsmask is locklessly accessed from rcutree_dying_cpu(). This
may help avoid load tearing due to concurrent access, KCSAN
issues, and preserve sanity of people reading the mask in tracing.

Reviewed-by: default avatarFrederic Weisbecker <frederic@kernel.org>
Signed-off-by: default avatarJoel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
parent b5ad0d2e

kernel/rcu/tree.c

+1 −1
Original line number Diff line number Diff line
@@ -2106,7 +2106,7 @@ int rcutree_dying_cpu(unsigned int cpu) 
	if (!IS_ENABLED(CONFIG_HOTPLUG_CPU))

		return 0;



	blkd = !!(rnp->qsmask & rdp->grpmask);

	blkd = !!(READ_ONCE(rnp->qsmask) & rdp->grpmask);

	trace_rcu_grace_period(rcu_state.name, READ_ONCE(rnp->gp_seq),

			       blkd ? TPS("cpuofl-bgp") : TPS("cpuofl"));

	return 0;