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[Qemu-devel] Re: [PATCH] qemu: work around for "posix-aio-compat"
From: |
Michael S. Tsirkin |
Subject: |
[Qemu-devel] Re: [PATCH] qemu: work around for "posix-aio-compat" |
Date: |
Wed, 21 Oct 2009 19:35:16 +0200 |
User-agent: |
Mutt/1.5.19 (2009-01-05) |
On Wed, Oct 21, 2009 at 07:28:54PM +0200, Paolo Bonzini wrote:
>> I've uploaded them here:
>> http://www.kernel.org/pub/linux/kernel/people/mst/
>> you can't see them in mirrors yet but will be able to soon when
>> kernel.org mirroring system catches them.
>
> There is no difference in optimizations except that here:
>
> for (i = 0; i < aiocb->aio_niov && count; ++i) {
>
> one of the two versions actually does "count && i < aiocb->aio_niov" due
> to hashing vagaries. This is irrelevant anyway. Same inlining, same
> loop optimization decisions, same everything else. So a GCC bug can be
> ruled out, IMHO.
>
> The only difference, as someone already suspected, is the padding---the
> sigset is placed between the top of the frame and the other variables,
> which may hide an overrun. This is quite amazing for a function that
> has no arrays, but still is the only evidence.
>
> I suggest trying to make the sigset_t static, since that generates
> exactly the same code as the "nohang" case, and exactly the same stack
> layout as the "hang" case. The next obvious step would be placing a
> watchpoint somewhere.
Yes, but where?
> Cheers,
>
> Paolo
[Qemu-devel] Re: [PATCH] qemu: work around for "posix-aio-compat", Michael S. Tsirkin, 2009/10/08
Re: [Qemu-devel] [PATCH] qemu: work around for "posix-aio-compat", Mark McLoughlin, 2009/10/20
- [Qemu-devel] Re: [PATCH] qemu: work around for "posix-aio-compat", Paolo Bonzini, 2009/10/20
- [Qemu-devel] Re: [PATCH] qemu: work around for "posix-aio-compat", Michael S. Tsirkin, 2009/10/21
- [Qemu-devel] Re: [PATCH] qemu: work around for "posix-aio-compat", Michael S. Tsirkin, 2009/10/21
- [Qemu-devel] Re: [PATCH] qemu: work around for "posix-aio-compat", Paolo Bonzini, 2009/10/21
- [Qemu-devel] Re: [PATCH] qemu: work around for "posix-aio-compat",
Michael S. Tsirkin <=
- [Qemu-devel] Re: [PATCH] qemu: work around for "posix-aio-compat", Paolo Bonzini, 2009/10/21
- [Qemu-devel] Re: [PATCH] qemu: work around for "posix-aio-compat", Michael S. Tsirkin, 2009/10/21
- [Qemu-devel] Re: [PATCH] qemu: work around for "posix-aio-compat", Paolo Bonzini, 2009/10/21