Commit 96050c68 authored Apr 20, 2019 by Paul E. McKenney

rcu: Upgrade sync_exp_work_done() to smp_mb()

The sync_exp_work_done() function uses smp_mb__before_atomic(), but
there is no obvious atomic in the ensuing code. The ordering is
absolutely required for grace periods to work correctly, so this
commit upgrades the smp_mb__before_atomic() to smp_mb().

Fixes: 6fba2b37 ("rcu: Remove deprecated RCU debugfs tracing code")
Reported-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>

parent 714b6904

kernel/rcu/tree_exp.h

+1 −2

Original line number	Diff line number	Diff line
		@@ -259,8 +259,7 @@ static bool sync_exp_work_done(unsigned long s)
		{
		if (rcu_exp_gp_seq_done(s)) {
		trace_rcu_exp_grace_period(rcu_state.name, s, TPS("done"));
		/* Ensure test happens before caller kfree(). */
		smp_mb__before_atomic(); /* ^^^ */
		smp_mb(); /* Ensure test happens before caller kfree(). */
		return true;
		}
		return false;

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