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Date: Fri, 2 Oct 2015 14:52:44 +0300
From: Riku Voipio <riku.voipio@iki.fi>
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Subject: Re: [Qemu-devel] [PATCH 00/34] linux-user: Fix signal race
 conditions and SA_RESTART
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: Timothy E Baldwin <T.E.Baldwin99@members.leeds.ac.uk>, QEMU Developers <qemu-devel@nongnu.org>

Hi Timothy,

On Thu, Sep 10, 2015 at 07:00:18PM +0100, Peter Maydell wrote:
> On 6 September 2015 at 00:56, Timothy E Baldwin
> <T.E.Baldwin99@members.leeds.ac.uk> wrote:
> > There are many races with signals in linux user:
> >
> >  - Multiple host signals in quick succession, fixed by keeping host signals
> >    blocked, and checking if target signals are blocked before calling
> >    target signal handler.
> >  - Signal shortly before blocking system call, fixed by either:
> >    - Block hosts signals, check and use host system call with
> >      sigset_t parameter.
> >    - Or check if signals are pending immediately before host system call
> >      and if a signal arrives between the check and system call rewind
> >      host instruction pointer to before the check. Also fixes SA_RESTART.
> >  - Signal before or during sensitive system call, fixed in a similar manner.
> >  - Close host and synchronous signals, partly fixed by implementing a separate
> >    queue for synchronous signals which are dispatched first. The asynchronous
> >    signal may still be delayed or lost rather than dispatched to another thread
> >    or handled after exec().
> >
> > Also fixed:
> >  - Errno array bounds.
> >  - Default fatal actions occurring in the middle of target instructions.
> 
> Thanks for sending this patchset. This is really cool and we've needed
> it for a long time...

Indeed, this would be nice to have for Qemu 2.5. Do you have time to
work through Peters comments and send an updated round of patches?

Riku