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Re: [Qemu-devel] qemu-nbd vs 'simple' trace backend vs iotest 147
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] qemu-nbd vs 'simple' trace backend vs iotest 147 |
Date: |
Wed, 11 Jul 2018 14:06:17 +0100 |
User-agent: |
Mutt/1.10.0 (2018-05-17) |
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().
Stefan
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