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Re: [Qemu-devel] Re: [5578] Increase default IO timeout from 10ms to 5s
From: |
Jan Kiszka |
Subject: |
Re: [Qemu-devel] Re: [5578] Increase default IO timeout from 10ms to 5s |
Date: |
Tue, 04 Nov 2008 18:10:03 +0100 |
User-agent: |
Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 |
M. Warner Losh wrote:
> In message: <address@hidden>
> Jamie Lokier <address@hidden> writes:
> : andrzej zaborowski wrote:
> : > > My man page even warns that the Linux
> : > > kernel is not implementing it yet, though I don't think this still
> : > > applies to recent 2.6.2x kernels.
> : >
> : > According to the man page it moved to kernel at 2.6.16 but the glibc
> : > wrapper should be ok too.
> :
> : If there's a glibc wrapper, it cannot be reliable...
> :
> : *Looks at glibc source*
> :
> : That's right. The glibc pselect() wrapper has the same race condition
> : which prompted this QEMU bug. If the signal arrives after unmasking
> : and before select() in the wrapper, then blocks.
> :
> : In other words, don't use pselect() if you might run on a kernel older
> : than 2.6.16, or on a host architecture which adds pselect() in a later
> : kernel version. Also, I wouldn't be surprised if older versions of
> : some BSDs have similar dodgy wrappers.
>
> Which ones have a good kernel implementation of it? FreeBSD's is
> currently approximately:
>
> if (!mask)
> _sigprocmask(mask, &oldmask);
> /* here */
> select();
> if (!mask)
> _sigprocmask(oldmask, NULL);
>
> I'm assuming that the problem is due to a signal arriving at /* here */.
I guess those things happen under some kind of preemption lock,
otherwise it would be a really poor implementation.
However, think we buried the idea of using pselect for this anyway.
Jan
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- [Qemu-devel] Re: [5578] Increase default IO timeout from 10ms to 5s, (continued)
- [Qemu-devel] Re: [5578] Increase default IO timeout from 10ms to 5s, Anthony Liguori, 2008/11/03
- [Qemu-devel] Re: [5578] Increase default IO timeout from 10ms to 5s, Jan Kiszka, 2008/11/03
- [Qemu-devel] Re: [5578] Increase default IO timeout from 10ms to 5s, Jan Kiszka, 2008/11/03
- [Qemu-devel] Re: [5578] Increase default IO timeout from 10ms to 5s, Anthony Liguori, 2008/11/03
- [Qemu-devel] Re: [5578] Increase default IO timeout from 10ms to 5s, Jan Kiszka, 2008/11/03
- Re: [Qemu-devel] Re: [5578] Increase default IO timeout from 10ms to 5s, andrzej zaborowski, 2008/11/04
- Re: [Qemu-devel] Re: [5578] Increase default IO timeout from 10ms to 5s, Jan Kiszka, 2008/11/04
- Re: [Qemu-devel] Re: [5578] Increase default IO timeout from 10ms to 5s, andrzej zaborowski, 2008/11/04
- Re: [Qemu-devel] Re: [5578] Increase default IO timeout from 10ms to 5s, Jamie Lokier, 2008/11/04
- Re: [Qemu-devel] Re: [5578] Increase default IO timeout from 10ms to 5s, M. Warner Losh, 2008/11/04
- Re: [Qemu-devel] Re: [5578] Increase default IO timeout from 10ms to 5s,
Jan Kiszka <=
- Re: [Qemu-devel] Re: [5578] Increase default IO timeout from 10ms to 5s, M. Warner Losh, 2008/11/04
- Re: [Qemu-devel] Re: [5578] Increase default IO timeout from 10ms to 5s, Jan Kiszka, 2008/11/04
- Re: [Qemu-devel] Re: [5578] Increase default IO timeout from 10ms to 5s, Jamie Lokier, 2008/11/05
- Re: [Qemu-devel] Re: [5578] Increase default IO timeout from 10ms to 5s, M. Warner Losh, 2008/11/05
- Re: [Qemu-devel] Re: [5578] Increase default IO timeout from 10ms to 5s, Jan Kiszka, 2008/11/05
- Re: [Qemu-devel] Re: [5578] Increase default IO timeout from 10ms to 5s, Daniel P. Berrange, 2008/11/05
- Re: [Qemu-devel] Re: [5578] Increase default IO timeout from 10ms to 5s, andrzej zaborowski, 2008/11/05
- Re: [Qemu-devel] Re: [5578] Increase default IO timeout from 10ms to 5s, Daniel P. Berrange, 2008/11/05
- Re: [Qemu-devel] Re: [5578] Increase default IO timeout from 10ms to 5s, Jamie Lokier, 2008/11/05
- Re: [Qemu-devel] Re: [5578] Increase default IO timeout from 10ms to 5s, Jamie Lokier, 2008/11/05