[Qemu-devel] Re: [PATCH] Revert "posix-aio-compat: avoid signal race when spawning a thread"

[Michael S. Tsirkin]

On Thu, Oct 08, 2009 at 12:54:00AM +0400, malc wrote:
> On Wed, 7 Oct 2009, Michael S. Tsirkin wrote:
> 
> > On Wed, Oct 07, 2009 at 11:28:21AM -0500, Anthony Liguori wrote:
> > >
> > >> There's nothing to review in this particular case, the thing was plain
> > >> broken, besides same thing was already discussed between me and
> > >> Andrzej, see for instance:
> > >> http://www.mail-archive.com/address@hidden/msg09542.html
> > >>
> > >> Needless to say the revert is broken also.
> > >>   
> > >
> > > Yeah, I understand the race the original commit fixes but I don't  
> > > understand how the original commit broke WinXP.
> > >
> > > Do you have further insight Michael?
> > 
> > My guess is that SIGALARM gets lost, this somehow leads to
> > disk request to timeout. Possible?
> 
> Being delayed - possible, being lost - violation of the spec.

I see this:

        The  use of sigprocmask() is unspecified in a
        multithreaded process; see pthread_sigmask(3).

Does it matter?

> > 
> > > Blindly reverting something that  appears right because of a
> > > regression is likely just papering over a  bigger problem.
> > >
> > > Regards,
> > >
> > > Anthony Liguori
> > >
> > 
> 
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