On Tue, Feb 08, 2011 at 08:11:08PM +0800, Yong Zhang wrote:
> 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()));

Only suppressing the warning is not enough here :(

>  #ifdef CONFIG_TRACE_IRQFLAGS
>  	local_irq_disable();


The semantic "called with irqs_disabled" is showed on several place
of _local_bh_enable_ip().

Need more thinking about it...