[PATCH 1/2] softirq: introduce loacal_bh_enable_force_wake()

[Yong Zhang <yong.zhang0@gmail.com>]

On Thu, Feb 03, 2011 at 06:17:39PM +0800, Yong Zhang wrote:
> Maybe we can introduce another type of local_bh_enable() in which
> waking up ksoftirqd is forced if needed.

---
From: Yong Zhang <yong.zhang0@gmail.com>
Subject: [PATCH 1/2] softirq: introduce loacal_bh_enable_force_wake()

If there is pending softirq, don't handle it in the caller's
context, invoke ksoftirqd directly instead.

del_timer_sync() will be the first caller.

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Andrew Morton <akpm@linux-foundation.org>
---
 include/linux/bottom_half.h |    1 +
 kernel/softirq.c            |   19 ++++++++++++++-----
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/include/linux/bottom_half.h b/include/linux/bottom_half.h
index 27b1bcf..665d697 100644
--- a/include/linux/bottom_half.h
+++ b/include/linux/bottom_half.h
@@ -5,5 +5,6 @@ extern void local_bh_disable(void);
 extern void _local_bh_enable(void);
 extern void local_bh_enable(void);
 extern void local_bh_enable_ip(unsigned long ip);
+extern void local_bh_enable_force_wake(void);
 
 #endif /* _LINUX_BH_H */
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 68eb5ef..5f224d4 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -154,7 +154,7 @@ void _local_bh_enable(void)
 
 EXPORT_SYMBOL(_local_bh_enable);
 
-static inline void _local_bh_enable_ip(unsigned long ip)
+static inline void _local_bh_enable_ip(unsigned long ip, bool force_wake)
 {
 	WARN_ON_ONCE(in_irq() || irqs_disabled());
 #ifdef CONFIG_TRACE_IRQFLAGS
@@ -171,8 +171,12 @@ static inline void _local_bh_enable_ip(unsigned long ip)
  	 */
 	sub_preempt_count(SOFTIRQ_DISABLE_OFFSET - 1);
 
-	if (unlikely(!in_interrupt() && local_softirq_pending()))
-		do_softirq();
+	if (unlikely(!in_interrupt() && local_softirq_pending())) {
+		if (!force_wake)
+			do_softirq();
+		else
+			wakeup_softirqd();
+	}
 
 	dec_preempt_count();
 #ifdef CONFIG_TRACE_IRQFLAGS
@@ -183,16 +187,21 @@ static inline void _local_bh_enable_ip(unsigned long ip)
 
 void local_bh_enable(void)
 {
-	_local_bh_enable_ip((unsigned long)__builtin_return_address(0));
+	_local_bh_enable_ip((unsigned long)__builtin_return_address(0), false);
 }
 EXPORT_SYMBOL(local_bh_enable);
 
 void local_bh_enable_ip(unsigned long ip)
 {
-	_local_bh_enable_ip(ip);
+	_local_bh_enable_ip(ip, false);
 }
 EXPORT_SYMBOL(local_bh_enable_ip);
 
+void local_bh_enable_force_wake(void)
+{
+	_local_bh_enable_ip((unsigned long)__builtin_return_address(0), true);
+}
+EXPORT_SYMBOL(local_bh_enable_force_wake);
 /*
  * We restart softirq processing MAX_SOFTIRQ_RESTART times,
  * and we fall back to softirqd after that.
-- 
1.7.1