rcu/nocb: Only cancel nocb timer if not polling

This commit refrains deleting the ->nocb_timer if rcu_nocb is polling
because it should not ever have been queued in the polling case.

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 4253a0ecc14fd6a380cb6b530f1ecd6ec2bc4c3d..db28e3123f32bb8cab4a12423e4fe258fd9015ef 100644 (file)
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -2176,18 +2176,18 @@ static void nocb_gp_wait(struct rcu_data *my_rdp)
        my_rdp->nocb_gp_gp = needwait_gp;
        my_rdp->nocb_gp_seq = needwait_gp ? wait_gp_seq : 0;
        if (bypass) {
-               raw_spin_lock_irqsave(&my_rdp->nocb_gp_lock, flags);
-               // Avoid race with first bypass CB.
-               if (my_rdp->nocb_defer_wakeup > RCU_NOCB_WAKE_NOT) {
-                       WRITE_ONCE(my_rdp->nocb_defer_wakeup, RCU_NOCB_WAKE_NOT);
-                       del_timer(&my_rdp->nocb_timer);
-               }
                if (!rcu_nocb_poll) {
+                       raw_spin_lock_irqsave(&my_rdp->nocb_gp_lock, flags);
+                       // Avoid race with first bypass CB.
+                       if (my_rdp->nocb_defer_wakeup > RCU_NOCB_WAKE_NOT) {
+                               WRITE_ONCE(my_rdp->nocb_defer_wakeup, RCU_NOCB_WAKE_NOT);
+                               del_timer(&my_rdp->nocb_timer);
+                       }
                        // At least one child with non-empty ->nocb_bypass, so set
                        // timer in order to avoid stranding its callbacks.
                        mod_timer(&my_rdp->nocb_bypass_timer, j + 2);
+                       raw_spin_unlock_irqrestore(&my_rdp->nocb_gp_lock, flags);
                }
-               raw_spin_unlock_irqrestore(&my_rdp->nocb_gp_lock, flags);
        }
        if (rcu_nocb_poll) {
                /* Polling, so trace if first poll in the series. */