On 06/17/2009 04:55 AM, Kyle McMartin wrote:
On Tue, Jun 16, 2009 at 10:51:48PM +0200, Helge Deller wrote:
On 06/15/2009 01:20 AM, John David Anglin wrote:
I am convinced that interrupts need to be disabled on SMP kernels to
prevent deadlock. On UP kernels, I am not convinced that anything bad
happens if we do a tlb purge while handling an interrupt since we don't
have to worry about preventing bus conflicts. The UP code can't
deadlock. I'm thinking that we can stay with disabling preemption.
Dave is right and it took me long to understand his point...
I continued testing and we can simply just disable preemption for UP
kernels and use an irq-safe spinlock for SMP kernels.
Below is the latest and greatest patch which fixes this bug.
Run-tested onUP kernels and compile-tested on SMP kernels.
Ugh, I'd really prefer it if we just took the irq disable and enable hit
on UP by making the codepaths the same... Is that ok with you or?
You mean to use the irq-safe spinlocking path for SMP _and_ UP?
Yes, that would be ok for me too. We just thought why we should try to save
some cycles on UP if possible, as the UP-kernel often is used on
slower machines where it would be beneficial for them...
If yes, do you want me to send an updated patch?
Helge
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