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Re: [Qemu-block] [Qemu-devel] qemu-nbd vs 'simple' trace backend vs iote
From: |
Cornelia Huck |
Subject: |
Re: [Qemu-block] [Qemu-devel] qemu-nbd vs 'simple' trace backend vs iotest 147 |
Date: |
Wed, 11 Jul 2018 15:15:45 +0200 |
On Wed, 11 Jul 2018 14:06:17 +0100
Stefan Hajnoczi <address@hidden> wrote:
> On Mon, Jul 09, 2018 at 03:45:49PM +0200, Cornelia Huck wrote:
> > Hi,
> >
> > I recently noticed that iotest 147 was hanging on my laptop, but worked
> > fine on my s390x LPAR. Turned out that the architecture was a red
> > herring; on both platforms, things fail with the 'simple' trace backend
> > and work with e.g. the 'log' trace backend. Some details on the
> > failures with the 'simple' backend:
> >
> > - The first run of 147 passes. However, there are two processes hanging
> > around, one using a unix socket and one using an inet socket:
> >
> > cohuck 22912 0.0 0.0 156580 3836 ? Ss 14:32 0:00
> > /home/cohuck/git/qemu/build/tests/qemu-iotests/../../qemu-nbd --fork -f
> > qcow2 /home/cohuck/git/qemu/build/tests/qemu-iotests/scratch/test.img -p
> > 10811
> > cohuck 22925 0.0 0.0 156580 3840 ? Ss 14:32 0:00
> > /home/cohuck/git/qemu/build/tests/qemu-iotests/../../qemu-nbd --fork -f
> > qcow2 /home/cohuck/git/qemu/build/tests/qemu-iotests/scratch/test.img -k
> > /home/cohuck/git/qemu/build/tests/qemu-iotests/scratch/nbd.socket
> >
> > Attaching a gdb shows that we seem to be waiting on flushing:
> >
> > (gdb) bt
> > #0 0x00007f461c078b99 in syscall () from /lib64/libc.so.6
> > #1 0x00007f461d13650f in g_cond_wait () from /lib64/libglib-2.0.so.0
> > #2 0x0000560cf3a1caf2 in flush_trace_file (wait=255)
> > at /home/cohuck/git/qemu/trace/simple.c:139
> > #3 st_flush_trace_buffer () at /home/cohuck/git/qemu/trace/simple.c:374
> > #4 0x00007f461bfc01d8 in __run_exit_handlers () from /lib64/libc.so.6
> > #5 0x00007f461bfc022a in exit () from /lib64/libc.so.6
> > #6 0x0000560cf392eb7e in main (argc=<optimized out>, argv=<optimized out>)
> > at /home/cohuck/git/qemu/qemu-nbd.c:1076
> >
> > (for both processes)
>
> Please also print backtraces for the other threads:
>
> (gdb) thread apply all bt
>
> There should be another thread in writeout_thread() so I'm surprised
> that flush_trace_file() is getting stuck in g_cond_wait().
I'll re-run to check, but there was only one thread in the process in
question.