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 <[email protected]> --- kernel/rcu/tree_exp.h | 1 + 1 file changed, 1 insertion(+) 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; } /* -- 2.17.1
