Re: intermittent hang in qos-test for qemu-system-i386 on 32-bit arm host

[Kevin Wolf <kwolf@redhat.com>]

Am 11.07.2021 um 17:53 hat Peter Maydell geschrieben:
> On Sat, 10 Jul 2021 at 14:30, Peter Maydell <peter.maydell@linaro.org> wrote:
> >
> > I've noticed recently that intermittently 'make check' will hang on
> > my aarch32 test system (really an aarch64 box with an aarch32 chroot).
> >
> > I think from grep that this must be the vhost-user-blk test.
> 
> I've also now seen this on qemu-system-i386 guest x86-64 Linux host:

Your two stack traces look very different to me, the common thing is
just that one process requests something and the other seems to have
ignored it and is just idle.

In the first stack trace, it was the qtest sending the very first
command ('endianness') over the qtest socket and QEMU seemed to ignore
it. In the second stack trace, it is the vhost-user-blk realize() code
in QEMU sending a request to the export in qemu-storage-daemon and never
getting an answer.

If this is the same bug, it looks to me as if it's something with the
event notification in the main loop? Can we check if there would
actually be an event pending in the apparently idle process if ppoll()
returned?

Kevin