Date: Fri, 6 Sep 2013 00:56:50 +0200
From: Frederic Weisbecker <fweisbec@gmail.com>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@au1.ibm.com>, Ingo Molnar <mingo@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        James Hogan <james.hogan@imgtec.com>,
        "James E.J. Bottomley" <jejb@parisc-linux.org>,
        Helge Deller <deller@gmx.de>,
        Martin Schwidefsky <schwidefsky@de.ibm.com>,
        Heiko Carstens <heiko.carstens@de.ibm.com>,
        "David S. Miller" <davem@davemloft.net>,
        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 3/3] irq: Comment on the use of inline stack for ksoftirq
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On Thu, Sep 05, 2013 at 05:33:24PM +0200, Frederic Weisbecker wrote:
> Ksoftirqd shouldn't need softirq stack since it's executing
> in a kernel thread with a callstack that is only beginning at
> this stage.
> 
> Lets comment about that for clarity.
> 
> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Paul Mackerras <paulus@au1.ibm.com>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: H. Peter Anvin <hpa@zytor.com>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: Paul Mackerras <paulus@au1.ibm.com>
> Cc: James Hogan <james.hogan@imgtec.com>
> Cc: James E.J. Bottomley <jejb@parisc-linux.org>
> Cc: Helge Deller <deller@gmx.de>
> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
> Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
> Cc: David S. Miller <davem@davemloft.net>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> ---
>  kernel/softirq.c |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
> 
> diff --git a/kernel/softirq.c b/kernel/softirq.c
> index 657e047..1de0322 100644
> --- a/kernel/softirq.c
> +++ b/kernel/softirq.c
> @@ -759,6 +759,7 @@ static void run_ksoftirqd(unsigned int cpu)
>  {
>  	local_irq_disable();
>  	if (local_softirq_pending()) {
> +		/* No need to use softirq stack here */

Looking at that comment now, it probably deserve more details :)

>  		__do_softirq();
>  		rcu_note_context_switch(cpu);
>  		local_irq_enable();
> -- 
> 1.7.5.4
> 
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