From efcd2d543685f377efda09e1ee84dacbda545523 Mon Sep 17 00:00:00 2001 From: Byungchul Park Date: Wed, 28 Feb 2018 14:49:02 +0900 Subject: [PATCH] rcu: Call wake_nocb_leader_defer() with 'FORCE' when nocb_q_count is high If an excessive number of callbacks have been queued, but the NOCB leader kthread's wakeup must be deferred, then we should wake up the leader unconditionally once it is safe to do so. This was handled correctly in commit fbce7497ee ("rcu: Parallelize and economize NOCB kthread wakeups"), but then commit 8be6e1b15c ("rcu: Use timer as backstop for NOCB deferred wakeups") passed RCU_NOCB_WAKE instead of the correct RCU_NOCB_WAKE_FORCE to wake_nocb_leader_defer(). As an interesting aside, RCU_NOCB_WAKE_FORCE is never passed to anything, which should have been taken as a hint. ;-) This commit therefore passes RCU_NOCB_WAKE_FORCE instead of RCU_NOCB_WAKE to wake_nocb_leader_defer() when a callback is queued onto a NOCB CPU that already has an excessive number of callbacks pending. Signed-off-by: Byungchul Park Signed-off-by: Paul E. McKenney Tested-by: Nicholas Piggin --- kernel/rcu/tree_plugin.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 3566e4f6dfcc..12774c4fb546 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -1957,7 +1957,7 @@ static void __call_rcu_nocb_enqueue(struct rcu_data *rdp, trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("WakeOvf")); } else { - wake_nocb_leader_defer(rdp, RCU_NOCB_WAKE, + wake_nocb_leader_defer(rdp, RCU_NOCB_WAKE_FORCE, TPS("WakeOvfIsDeferred")); } rdp->qlen_last_fqs_check = LONG_MAX / 2; -- GitLab