Commit b0c18c87 authored Jan 03, 2020 by Paul E. McKenney

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@kernel.org>

parent 7672d647

kernel/rcu/tree_exp.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -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"));