Commit 383e1332 authored May 23, 2019 by Paul E. McKenney

rcu/nocb: Never downgrade ->nocb_defer_wakeup in wake_nocb_gp_defer()



Currently, wake_nocb_gp_defer() simply stores whatever waketype was
passed in, which can result in a RCU_NOCB_WAKE_FORCE being downgraded
to RCU_NOCB_WAKE, which could in turn delay callback processing.
This commit therefore adds a check so that wake_nocb_gp_defer() only
updates ->nocb_defer_wakeup when the update increases the forcefulness,
thus avoiding downgrades.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>

parent aeeacd9d

kernel/rcu/tree_plugin.h

+2 −1

Original line number	Diff line number	Diff line
		@@ -1600,6 +1600,7 @@ static void wake_nocb_gp_defer(struct rcu_data *rdp, int waketype,
		{
		if (rdp->nocb_defer_wakeup == RCU_NOCB_WAKE_NOT)
		mod_timer(&rdp->nocb_timer, jiffies + 1);
		if (rdp->nocb_defer_wakeup < waketype)
		WRITE_ONCE(rdp->nocb_defer_wakeup, waketype);
		trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, reason);
		}

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