Re: [PATCH 3/3] irq: Comment on the use of inline stack for ksoftirq

[Frederic Weisbecker]

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@xxxxxxxxx>
> Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
> Cc: Paul Mackerras <paulus@xxxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: H. Peter Anvin <hpa@xxxxxxxxx>
> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Cc: Paul Mackerras <paulus@xxxxxxxxxxx>
> Cc: James Hogan <james.hogan@xxxxxxxxxx>
> Cc: James E.J. Bottomley <jejb@xxxxxxxxxxxxxxxx>
> Cc: Helge Deller <deller@xxxxxx>
> Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
> Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
> Cc: David S. Miller <davem@xxxxxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> ---
>  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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