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From: Max Reitz <mreitz@redhat.com>
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Date: Fri, 23 Feb 2018 14:03:15 +0100
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Subject: [Qemu-devel] Intermittent failure of iotest 203
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From: Max Reitz <mreitz@redhat.com>
To: Qemu-block <qemu-block@nongnu.org>
Cc: "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
 Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <60d1e2ab-c3a4-cae2-b810-5e46dc124b0b@redhat.com>
Subject: Intermittent failure of iotest 203
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Hi,

iotest 203 relatively often fails for me, at least when run in parallel.
 When I run the following concurrently on four shells:

$ while TEST_DIR=3D/tmp/t1 ./check -T -qcow2 203; do; done
$ while TEST_DIR=3D/tmp/t2 ./check -T -qcow2 203; do; done
$ while TEST_DIR=3D/tmp/t3 ./check -T -qcow2 203; do; done
$ while TEST_DIR=3D/tmp/t4 ./check -T -qcow2 203; do; done

Very quickly (like under ten iterations), at least one of those starts
to hang and then fails because of a timeout in vm.get_qmp_event().

Before digging deeper into the ppoll() dungeon* myself, I decided to
report this so I wouldn't have to. :-)

*Backtrace:

(gdb) bt
#0  0x00007f354137b4d6 in ppoll () at /lib64/libc.so.6
#1  0x000055b659144299 in ppoll (__ss=3D0x0, __timeout=3D0x7ffe4eaca230,
__nfds=3D<optimized out>, __fds=3D<optimized out>) at
/usr/include/bits/poll2.h:77
#2  0x000055b659144299 in qemu_poll_ns (fds=3D<optimized out>,
nfds=3D<optimized out>, timeout=3Dtimeout@entry=3D39512999619000) at
util/qemu-timer.c:334
#3  0x000055b6591450a3 in os_host_main_loop_wait (timeout=3D<optimized
out>) at util/main-loop.c:255
#4  0x000055b6591450a3 in main_loop_wait (nonblocking=3D<optimized out>)
at util/main-loop.c:515
#5  0x000055b658d4a253 in main_loop () at vl.c:1933
#6  0x000055b658d4a253 in main (argc=3D<optimized out>, argv=3D<optimized=

out>, envp=3D<optimized out>) at vl.c:4757

Max


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