From 383e13328373ae1e17119ff89c86ff5f9413f31c Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 23 May 2019 13:49:26 -0700 Subject: 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 --- kernel/rcu/tree_plugin.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'kernel/rcu') diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 7077ef7bea96..b9e00660af60 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -1600,7 +1600,8 @@ 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); - WRITE_ONCE(rdp->nocb_defer_wakeup, waketype); + if (rdp->nocb_defer_wakeup < waketype) + WRITE_ONCE(rdp->nocb_defer_wakeup, waketype); trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, reason); } -- cgit v1.2.3