From c4fa43e875b5f4ba9a6d0ff8bec5c0d2efe3c706 Mon Sep 17 00:00:00 2001 From: Nicholas Mc Guire Date: Fri, 6 Dec 2013 00:42:22 +0100 Subject: softirq: make migrate disable/enable conditioned on softirq_nestcnt transition This patch removes the recursive calls to migrate_disable/enable in local_bh_disable/enable the softirq-local-lock.patch introduces local_bh_disable/enable wich decrements/increments the current->softirq_nestcnt and disable/enables migration as well. as softirq_nestcnt (include/linux/sched.h conditioned on CONFIG_PREEMPT_RT_BASE) already is tracking the nesting level of the recursive calls to local_bh_disable/enable (all in kernel/softirq.c) - no need to do it twice. migrate_disable/enable thus can be conditionsed on softirq_nestcnt making a transition from 0-1 to disable migration and 1-0 to re-enable it. No change of functional behavior, this does noticably reduce the observed nesting level of migrate_disable/enable Signed-off-by: Nicholas Mc Guire Reviewed-by: Steven Rostedt Signed-off-by: Sebastian Andrzej Siewior diff --git a/kernel/softirq.c b/kernel/softirq.c index 4d69177..15ad603 100644 --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -569,8 +569,8 @@ static void do_current_softirqs(int need_rcu_bh_qs) void local_bh_disable(void) { - migrate_disable(); - current->softirq_nestcnt++; + if (++current->softirq_nestcnt == 1) + migrate_disable(); } EXPORT_SYMBOL(local_bh_disable); @@ -584,8 +584,8 @@ void local_bh_enable(void) do_current_softirqs(1); local_irq_enable(); - current->softirq_nestcnt--; - migrate_enable(); + if (--current->softirq_nestcnt == 0) + migrate_enable(); } EXPORT_SYMBOL(local_bh_enable); @@ -597,8 +597,10 @@ EXPORT_SYMBOL(local_bh_enable_ip); void _local_bh_enable(void) { - current->softirq_nestcnt--; - migrate_enable(); + if (WARN_ON(current->softirq_nestcnt == 0)) + return; + if (--current->softirq_nestcnt == 0) + migrate_enable(); } EXPORT_SYMBOL(_local_bh_enable); -- cgit v0.10.2