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.
patch on top of 3.12.1-rt4
No change of functional behavior, this does noticably reduce the observed
nesting level of migrate_disable/enable
Signed-off-by: Nicholas Mc Guire <der.herr@xxxxxxx>
---
kernel/softirq.c | 14 ++++++++------
1 files changed, 8 insertions(+), 6 deletions(-)
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 9a7268f..16ebbd9 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);
--
1.7.2.5
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