Re: [PATCH] i386: Fix softirq accounting with 4K stacks

[Arjan van de Ven]

On Sun, 2006-06-25 at 19:44 +0200, Mike Galbraith wrote:
> On Sun, 2006-06-25 at 16:24 +0200, BjÃrn Steinbrink wrote:
> 
> > Still no idea why your "fix" works, but the following patch also fixes
> > the problem and is at least a little more like the RightThing.
> 
> Yeah.  I don't know about you, but I fully intend to blatantly ignore
> that 'why' ;-)

the why is relatively easy ;)

since the "is a softirq executing" bit is on the stack, and each context
(user, soft and hard irq) has their own stack, it's not automatic that
the hardirq stack gets the softirq-executing flag... which your patch
fixes.

NMI's and apic irqs generally don't go via the normal irq path and thus
don't do a stack switch... so they don't lose the bit (for accounting
purposes)


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