Re: [Xen-devel] Re: [Qemu-devel] [PATCH 01/13] Handle terminating signals.

[Ian Jackson]

Jamie Lokier writes ("Re: [Xen-devel] Re: [Qemu-devel] [PATCH 01/13] Handle 
terminating signals."):
> Ian Jackson wrote:
> > If you use aio, glibc has a tendency to emulate it with thread(s).
> > The helper thread I was referring to in my commit message is the
> > glibc-created helper thread.  glibc appears (in strace) to do IO in
> > this thread and then raises the signal you asked for (SIGUSR2 in
> > qemu's case).
> 
> That observation implies Anthony's helper thread will not always
> receive the SIGUSR2 signals - Glibc's thread may receive them instead.

Yes.  Err, I'm not sure what effect that will have in Anthony's patch
but it probably wouldn't be good.

As I say I haven't managed to reproduce this other than in a full
qemu-dm tree (from qemu-xen).

So it may be that it is because of something I did or something the
qemu-xen code does - although it seems hard to imagine how it could
break the signal mask in the helper thread given that that thread runs
entirely glibc code, except when a signal is being delivered (and of
course the signal mask is saved and restored for signal delivery).

Ian.