Re: [Qemu-devel] [PULL 00/18] Chardev patches

[Daniel P . Berrangé]

On Fri, Feb 08, 2019 at 11:44:42AM +0000, Peter Maydell wrote:
> On Thu, 7 Feb 2019 at 16:06, Marc-André Lureau
> <address@hidden> wrote:
> >
> > The following changes since commit 632351e0e1a861f2eaf709b053c53f96a1225825:
> >
> >   Merge remote-tracking branch 'remotes/elmarco/tags/dump-pull-request' 
> > into staging (2019-02-07 14:20:46 +0000)
> >
> > are available in the Git repository at:
> >
> >   https://github.com/elmarco/qemu.git tags/chardev-pull-request
> >
> > for you to fetch changes up to df3afdedd23ade0c9de55cadeb1d85055689023f:
> >
> >   tests/test-char: add muxed chardev testing for open/close (2019-02-07 
> > 16:18:25 +0100)
> >
> > ----------------------------------------------------------------
> > Various chardev fixes
> >
> > ----------------------------------------------------------------
> 
> This seems to result in 'make check' failures on some platforms.
> I saw this on s390 and aarch32, I think.
> 
> MALLOC_PERTURB_=${MALLOC_PERTURB_:-$(( ${RANDOM:-0} % 255 + 1))}
> tests/test-char -m=quick -k --tap < /dev/null |
> ./scripts/tap-driver.pl --test-name="test-char
> "
> PASS 1 test-char /char/null
> PASS 2 test-char /char/invalid
> PASS 3 test-char /char/ringbuf
> PASS 4 test-char /char/mux
> PASS 5 test-char /char/stdio
> PASS 6 test-char /char/pipe
> PASS 7 test-char /char/file
> PASS 8 test-char /char/file-fifo
> PASS 9 test-char /char/udp
> PASS 10 test-char /char/serial
> PASS 11 test-char /char/hotswap
> PASS 12 test-char /char/websocket
> PASS 13 test-char /char/socket/server/mainloop/tcp
> PASS 14 test-char /char/socket/server/mainloop/unix
> PASS 15 test-char /char/socket/server/wait-conn/tcp
> PASS 16 test-char /char/socket/server/wait-conn/unix
> PASS 17 test-char /char/socket/server/mainloop-fdpass/tcp
> PASS 18 test-char /char/socket/server/mainloop-fdpass/unix
> PASS 19 test-char /char/socket/server/wait-conn-fdpass/tcp
> PASS 20 test-char /char/socket/server/wait-conn-fdpass/unix
> PASS 21 test-char /char/socket/client/mainloop/tcp
> PASS 22 test-char /char/socket/client/mainloop/unix
> qemu: qemu_mutex_destroy: Device or resource busy
> PASS 23 test-char /char/socket/client/wait-conn/tcp
> PASS 24 test-char /char/socket/client/wait-conn/unix
> Aborted (core dumped)
> ERROR - too few tests run (expected 32, got 24)
> 
> Here's a backtrace from running tests/test-char under gdb.
> Looks like a race condition between a thread trying to
> destroy a mutex and a different thread that is still
> using it.

Thanks, that is very useful. I can see the race condition here
now between qio_task_thread_worker and qio_task_thread_result.
I need to acquire the mutex in qio_task_thread_result in order
to sycnhronize with completion of qio_task_thread_worker.

> 
> On some other hosts I saw a similar
> "qemu: qemu_mutex_destroy: Device or resource busy" and core dump in the
> migration tests, I think, which is probably the same underlying bug.

Yes, I expect it is the same problem


Regards,
Daniel
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