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Re: [Qemu-devel] qemu vl.c
From: |
andrzej zaborowski |
Subject: |
Re: [Qemu-devel] qemu vl.c |
Date: |
Tue, 18 Dec 2007 01:40:17 +0100 |
On 18/12/2007, Anders <address@hidden> wrote:
>
> >>>>> Redundant timer rearm optimisation by Anders Melchiorsen.
>
> > I'm merging qemu-cvs into the kvm repository now, and with this commit
> > in, kvm will hang after about a minute. Attaching to it with gdb or
> > strace will cause it to resume, so this is very likely a missing signal
> > problem.
>
> That is clearly not good.
>
> I still cannot see anything wrong with my patch. As fewer signals are
> delivered now, it is possible that this change highlights some old race.
Yes, I don't see anything wrong in this change either but I see how
the scenario given by Paul was already buggy before. Paul confirmed on
IRC that this is also what he meant.
I suspect it was buggy since "unix" and "rtc" stopped being the only
available clock sources.
> It is certainly also possible that my patch is all wrong, even if I am not
> able to see it.
>
>
> The next few days I will be travelling, but when I get back, I was
> planning to address Pauls concern by adding
>
> qemu_rearm_alarm_timer(alarm_timer);
That would be also my first guess at fixing this, but I have no good
test-case (obviously I wouldn't have committed the change if I had
such a test-case).
>
> to the bottom of qemu_mod_timer().
>
> If you feel like it, you can try that out. I am predicting that I will
> have a hard time reproducing your hang, as I have only been testing with
> kvm, and obviously not seen this problem yet.
>
> (What I really plan to add is a rearm only if the new timer is added at
> the head of the list, but the above should do for a test)
Attached is a small patch to do exactly this. The rearming in
main_loop_wait() can also be made conditional but I don't think there
would be a real gain.
Testing with KVM will be appreciated.
Regards
qemu-timers.patch
Description: Text Data
- [Qemu-devel] qemu vl.c, Andrzej Zaborowski, 2007/12/02
- [Qemu-devel] qemu vl.c, Andrzej Zaborowski, 2007/12/06
- [Qemu-devel] qemu vl.c, Andrzej Zaborowski, 2007/12/16
- [Qemu-devel] qemu vl.c, Andrzej Zaborowski, 2007/12/16
- Re: [Qemu-devel] qemu vl.c, Paul Brook, 2007/12/16
- Re: [Qemu-devel] qemu vl.c, Anders, 2007/12/16
- Re: [Qemu-devel] qemu vl.c, Paul Brook, 2007/12/16
- Re: [Qemu-devel] qemu vl.c, Avi Kivity, 2007/12/17
- Re: [Qemu-devel] qemu vl.c, Anders, 2007/12/17
- Re: [Qemu-devel] qemu vl.c,
andrzej zaborowski <=
- Re: [Qemu-devel] qemu vl.c, Avi Kivity, 2007/12/18
- Re: [Qemu-devel] qemu vl.c, Anders, 2007/12/18
[Qemu-devel] qemu vl.c, Andrzej Zaborowski, 2007/12/24