The "nocb_bypass_timer" ends up calling wake_nocb_gp() which deletes the pending "nocb_timer" (note they are not the same timers) for the given rdp without resetting the matching state stored in nocb_defer wakeup. As a result, a future call_rcu() on that rdp may be fooled and think the timer is armed when it's not, missing a deferred nocb_gp wakeup. Fix this with resetting rdp->nocb_defer_wakeup when we disarm the timer. Fixes: d1b222c6be1f (rcu/nocb: Add bypass callback queueing) Cc: Stable <stable@xxxxxxxxxxxxxxx> Cc: Josh Triplett <josh@xxxxxxxxxxxxxxxx> Cc: Lai Jiangshan <jiangshanlai@xxxxxxxxx> Cc: Joel Fernandes <joel@xxxxxxxxxxxxxxxxx> Cc: Neeraj Upadhyay <neeraju@xxxxxxxxxxxxxx> Cc: Boqun Feng <boqun.feng@xxxxxxxxx> Signed-off-by: Frederic Weisbecker <frederic@xxxxxxxxxx> --- kernel/rcu/tree_plugin.h | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 7e33dae0e6ee..a44f80d7661b 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -1705,6 +1705,8 @@ static bool wake_nocb_gp(struct rcu_data *rdp, bool force, rcu_nocb_unlock_irqrestore(rdp, flags); return false; } + + rdp->nocb_defer_wakeup = RCU_NOCB_WAKE_NOT; del_timer(&rdp->nocb_timer); rcu_nocb_unlock_irqrestore(rdp, flags); raw_spin_lock_irqsave(&rdp_gp->nocb_gp_lock, flags); -- 2.25.1
