From dd7c4d89730a1be2c1d361a8ae1f0fe9465ccf9c Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Fri, 27 Aug 2010 10:51:17 -0700 Subject: [PATCH] rcu: performance fixes to TINY_PREEMPT_RCU callback checking This commit tightens up checks in rcu_preempt_check_callbacks() to avoid unnecessary special handling at rcu_read_unlock() time. Signed-off-by: Paul E. McKenney --- kernel/rcutiny_plugin.h | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h index c5bea1137dcb..6ceca4f745ff 100644 --- a/kernel/rcutiny_plugin.h +++ b/kernel/rcutiny_plugin.h @@ -72,7 +72,7 @@ static void rcu_report_exp_done(void); /* * Return true if the CPU has not yet responded to the current grace period. */ -static int rcu_cpu_cur_gp(void) +static int rcu_cpu_blocking_cur_gp(void) { return rcu_preempt_ctrlblk.gpcpu != rcu_preempt_ctrlblk.gpnum; } @@ -229,7 +229,7 @@ void rcu_preempt_note_context_switch(void) * cannot end. */ list_add(&t->rcu_node_entry, &rcu_preempt_ctrlblk.blkd_tasks); - if (rcu_cpu_cur_gp()) + if (rcu_cpu_blocking_cur_gp()) rcu_preempt_ctrlblk.gp_tasks = &t->rcu_node_entry; } @@ -368,12 +368,16 @@ static void rcu_preempt_check_callbacks(void) { struct task_struct *t = current; - if (!rcu_preempt_running_reader() && rcu_preempt_gp_in_progress()) + if (rcu_preempt_gp_in_progress() && + (!rcu_preempt_running_reader() || + !rcu_cpu_blocking_cur_gp())) rcu_preempt_cpu_qs(); if (&rcu_preempt_ctrlblk.rcb.rcucblist != rcu_preempt_ctrlblk.rcb.donetail) raise_softirq(RCU_SOFTIRQ); - if (rcu_preempt_gp_in_progress() && rcu_preempt_running_reader()) + if (rcu_preempt_gp_in_progress() && + rcu_cpu_blocking_cur_gp() && + rcu_preempt_running_reader()) t->rcu_read_unlock_special |= RCU_READ_UNLOCK_NEED_QS; } -- 2.30.2