Re: lockdep: possible reason: unannotated irqs-off. (was: Re: Linux 2.6.38-rc4)

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

On Tue, Feb 08, 2011 at 11:41:52AM +0100, Peter Zijlstra wrote:
> Argh! Its an annotation nightmare that.. it didn't trigger for me when
> running that because I didn't have DEBUG_LOCKDEP=y.

Me too...

> 
> OK, let me try and come up with another way to annotate this
> del_timer_sync() muck,

Is my previous patch acceptable?

I inlined it as below(and updated based on linux-2.6.38-rc4)

---
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            |   21 +++++++++++++++------
 2 files changed, 16 insertions(+), 6 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..3c05dfa 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -154,9 +154,9 @@ 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());
+	WARN_ON_ONCE(in_irq() || (!force_wake && irqs_disabled()));
 #ifdef CONFIG_TRACE_IRQFLAGS
 	local_irq_disable();
 #endif
@@ -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