From: Paul E. McKenney Date: Wed, 28 Nov 2018 18:37:42 +0000 (-0800) Subject: rcu: Make expedited IPI handler return after handling critical section X-Git-Tag: v5.1-rc1~166^2^2~14 X-Git-Url: http://git.osdn.net/view?a=commitdiff_plain;h=1de462ed85062df2ab6939eeee1625e767052907;p=uclinux-h8%2Flinux.git rcu: Make expedited IPI handler return after handling critical section During expedited RCU grace-period initialization, IPIs are sent to all non-idle online CPUs. The IPI handler checks to see if the CPU is in quiescent state, reporting one if so. This handler looks at three different cases: (1) The CPU is not in an rcu_read_lock()-based critical section, (2) The CPU is in the process of exiting an rcu_read_lock()-based critical section, and (3) The CPU is in an rcu_read_lock()-based critical section. In case (2), execution falls through into case (3). This is harmless from a functionality viewpoint, but can result in needless overhead during an improbable corner case. This commit therefore adds the "return" statement needed to prevent fall-through. Signed-off-by: Paul E. McKenney --- diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h index 928fe5893a57..6d4eb4694b6f 100644 --- a/kernel/rcu/tree_exp.h +++ b/kernel/rcu/tree_exp.h @@ -697,6 +697,7 @@ static void sync_rcu_exp_handler(void *unused) WRITE_ONCE(t->rcu_read_unlock_special.b.exp_hint, true); } raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + return; } /*