From: Nicholas Mc Guire Date: Thu, 5 Dec 2013 23:42:22 +0000 (+0100) Subject: softirq: make migrate disable/enable conditioned on softirq_nestcnt transition X-Git-Url: https://rtime.felk.cvut.cz/gitweb/zynq/linux.git/commitdiff_plain/400f006a3bce2af648f7b1647f87a4f5718ade82 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 916ffed7bba3..588bae073f1e 100644 --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -557,8 +557,8 @@ static void do_current_softirqs(int need_rcu_bh_qs) static void __local_bh_disable(void) { - migrate_disable(); - current->softirq_nestcnt++; + if (++current->softirq_nestcnt == 1) + migrate_disable(); } void local_bh_disable(void) @@ -584,8 +584,8 @@ static void __local_bh_enable(void) do_current_softirqs(1); local_irq_enable(); - current->softirq_nestcnt--; - migrate_enable(); + if (--current->softirq_nestcnt == 0) + migrate_enable(); } void local_bh_enable(void) @@ -609,8 +609,10 @@ 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);