Commit 7672d647 authored Jan 03, 2020 by Paul E. McKenney

rcu: Add WRITE_ONCE() to rcu_node ->qsmask update



The rcu_node structure's ->qsmask 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@kernel.org>

parent 8a7e8f51

kernel/rcu/tree.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -1881,7 +1881,7 @@ static void rcu_report_qs_rnp(unsigned long mask, struct rcu_node *rnp,
		WARN_ON_ONCE(oldmask); /* Any child must be all zeroed! */
		WARN_ON_ONCE(!rcu_is_leaf_node(rnp) &&
		rcu_preempt_blocked_readers_cgp(rnp));
		rnp->qsmask &= ~mask;
		WRITE_ONCE(rnp->qsmask, rnp->qsmask & ~mask);
		trace_rcu_quiescent_state_report(rcu_state.name, rnp->gp_seq,
		mask, rnp->qsmask, rnp->level,
		rnp->grplo, rnp->grphi,

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