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

[malc <av1474@comtv.ru>]

On Wed, 7 Oct 2009, Michael S. Tsirkin wrote:

> 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/qemu-devel@nongnu.org/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?

One of the patches i've asked you to try today replaced sigprocmask with
pthread_sigmask, you've said it did nothing. In any case, strictly
speaking, the code is wrong, so yes it does matter in theory.

[..snip..]

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