Commit 59881bcd authored Jan 20, 2020 by Paul E. McKenney

rcu: Add WRITE_ONCE() to rcu_state ->gp_start



The rcu_state structure's ->gp_start 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 57721fd1

kernel/rcu/tree_stall.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -102,7 +102,7 @@ static void record_gp_stall_check_time(void)
		unsigned long j = jiffies;
		unsigned long j1;

		rcu_state.gp_start = j;
		WRITE_ONCE(rcu_state.gp_start, j);
		j1 = rcu_jiffies_till_stall_check();
		/* Record ->gp_start before ->jiffies_stall. */
		smp_store_release(&rcu_state.jiffies_stall, j + j1); /* ^^^ */

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