From: Frederic Weisbecker <frederic@kernel.org>
Date: Tue, 23 Feb 2021 00:10:05 +0000 (+0100)
Subject: rcu/nocb: Directly call __wake_nocb_gp() from bypass timer
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=c7ef7500a891432a3bb2b036f535bfdf58aa3605;p=linux.git

rcu/nocb: Directly call __wake_nocb_gp() from bypass timer

The bypass timer calls __call_rcu_nocb_wake() instead of directly
calling __wake_nocb_gp().  The only difference here is that
rdp->qlen_last_fqs_check gets overridden.  But resetting the deferred
force quiescent state base shouldn't be relevant for that timer.  In fact
the bypass queue in question can be for any rdp from the group and not
necessarily the rdp leader on which the bypass timer is attached.

This commit therefore calls __wake_nocb_gp() directly.  This way we
don't even need to lock the ->nocb_lock.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Neeraj Upadhyay <neeraju@codeaurora.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 5a2aa9c4e5695..82e9ffb923475 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -2015,9 +2015,10 @@ static void do_nocb_bypass_wakeup_timer(struct timer_list *t)
 	struct rcu_data *rdp = from_timer(rdp, t, nocb_bypass_timer);
 
 	trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("Timer"));
-	rcu_nocb_lock_irqsave(rdp, flags);
+
+	raw_spin_lock_irqsave(&rdp->nocb_gp_lock, flags);
 	smp_mb__after_spinlock(); /* Timer expire before wakeup. */
-	__call_rcu_nocb_wake(rdp, true, flags);
+	__wake_nocb_gp(rdp, rdp, false, flags);
 }
 
 /*