Re: intermittent failure, s390 host, x86-64 guest, vhost-user-blk test

[Raphael Norwitz]

On Wed, Aug 04, 2021 at 09:43:25AM -0400, Michael S. Tsirkin wrote:
> On Wed, Aug 04, 2021 at 01:40:37PM +0100, Peter Maydell wrote:
> > Saw this intermittent as part of my ad-hoc CI test setup.
> > The backtrace says that the QEMU process has somehow hung
> > during 'realize' of the vhost-user device...
> 
> Hmm seems to have to do with the daemon not responding ...
> Cc a bunch more people ...

On a recent master with the meson dependency fix (commit ID:
cc1838c25d55e7f478cd493431679337e24e1b72) I’ve been able to reproduce
this quite easily with the following command from the make check-qtest
V=1 output.

#!/bin/sh

 I="0"
 while [ true ] 
 do 
 echo "=== iteration $I ===" 

 ALLOC_PERTURB_=${MALLOC_PERTURB_:-$(( ${RANDOM:-0} % 255 + 1))} \
     QTEST_QEMU_IMG=./qemu-img \
     
G_TEST_DBUS_DAEMON=/home/raphael/pub_src/qemu_checkouts/qemu/tests/dbus-vmstate-daemon.sh
 \
     QTEST_QEMU_BINARY=./qemu-system-x86_64 \
     QTEST_QEMU_STORAGE_DAEMON_BINARY=./storage-daemon/qemu-storage-daemon \
     tests/qtest/qos-test --tap -k 

I=$((I+1)) 
done 

I typically hit it within 10 iterations.

Looking at the trace provided, we see that QEMU has sent a
VHOST_USER_GET_PROTOCOL_FEATURES message and is stuck waiting for a
reply. Meanwhile the storage-daemon is stuck waiting for a message. In
the vhost-user-blk-test, as of now there is nothing stoping
vhost-user-blk in QEMU writing to the socket right after forking off the
storage daemon before it has a chance to come up properly, leaving the
test hanging forever. I’ve seen this happen before with other
backends/device types. I added a one second sleep to the test case
after the test forks off the storage daemon, and it resolved the hang
completely for me. I ran the test for 1000+ iterations and couldn’t
reproduce the failure with the sleep.

I just mailed some patches which pipe the stdout of the storage-daemon
back to he vhost-user-blk-test. The storage-daemon prints a log when
it is fully initialized which wakes up vhost-user-blk-test. This
should reliably resolve the hang.

I’m thinking we could also change the vhost-user code to timeout (or
possibly retry?) if the first VHOST_USER_GET_PROTOCOL_FEATURES
message doesn’t receive a response, as it’s better to fail power-on then
hang forever. If others agree I can pull together an RFC.

> 
> > Process tree:
> > 
> > ubuntu   59552  0.0  0.0   5460  3120 ?        S    06:51   0:00
> >            \_ bash -o pipefail -c echo
> > 'MALLOC_PERTURB_=${MALLOC_PERTURB_:-$(( ${RANDOM:-0} % 255 + 1))}
> > QTEST_QEMU_IMG=./qemu-img
> > G_TEST_DBUS_DAEMON=/home/ubuntu/qemu/tests/dbus-vmstate-daemon.sh
> > QTEST_QEMU_BINARY=./qemu-system-x86_64
> > QTEST_QEMU_STORAGE_DAEMON_BINARY=./storage-daemon/qemu-storage-daemon
> > tests/qtest/qos-test --tap -k' &&
> > MALLOC_PERTURB_=${MALLOC_PERTURB_:-$(( ${RANDOM:-0} % 255 + 1))}
> > QTEST_QEMU_IMG=./qemu-img
> > G_TEST_DBUS_DAEMON=/home/ubuntu/qemu/tests/dbus-vmstate-daemon.sh
> > QTEST_QEMU_BINARY=./qemu-system-x86_64
> > QTEST_QEMU_STORAGE_DAEMON_BINARY=./storage-daemon/qemu-storage-daemon
> > tests/qtest/qos-test --tap -k -m quick < /dev/null |
> > ./scripts/tap-driver.pl --test-name="qtest-x86_64/qos-test"
> > ubuntu   59553  0.0  0.2  88008  8332 ?        Sl   06:51   0:00
> >                \_ tests/qtest/qos-test --tap -k -m quick
> > ubuntu   60122  0.0  0.5 254432 21516 ?        Sl   06:51   0:00
> >                |   \_ ./storage-daemon/qemu-storage-daemon --blockdev
> > driver=file,node-name=disk0,filename=qtest.trJnuR --export
> > type=vhost-user-blk,id=disk0,addr.type=unix,addr.path=/tmp/qtest-59553-sock.iRt6WL,node-name=disk0,writable=on,num-queues=1
> > ubuntu   60123  0.0  1.6 747952 62732 ?        Sl   06:51   0:00
> >                |   \_ ./qemu-system-x86_64 -qtest
> > unix:/tmp/qtest-59553.sock -qtest-log /dev/null -chardev
> > socket,path=/tmp/qtest-59553.qmp,id=char0 -mon
> > chardev=char0,mode=control -display none -M pc -device
> > vhost-user-blk-pci,id=drv0,chardev=char1,addr=4.0 -object
> > memory-backend-memfd,id=mem,size=256M,share=on -M memory-backend=mem
> > -m 256M -chardev socket,id=char1,path=/tmp/qtest-59553-sock.iRt6WL
> > -accel qtest
> > ubuntu   59554  0.0  0.2  14116 11204 ?        S    06:51   0:00
> >                \_ perl ./scripts/tap-driver.pl
> > --test-name=qtest-x86_64/qos-test
> > 
> > Backtrace, qemu process:
> > 
> > Thread 4 (Thread 0x3ff5be1d910 (LWP 60131)):
> > #0  0x000003ff7e2bed6a in __GI___sigtimedwait (set=<optimized out>,
> >     set@entry=0x3ff5be1a098, info=info@entry=0x3ff5be19f68,
> > timeout=timeout@entry=0x0)
> >     at ../sysdeps/unix/sysv/linux/sigtimedwait.c:42
> > #1  0x000003ff7e492ca8 in __sigwait (set=set@entry=0x3ff5be1a098,
> > sig=sig@entry=0x3ff5be1a094)
> >     at ../sysdeps/unix/sysv/linux/sigwait.c:28
> > #2  0x000002aa16891ab2 in dummy_cpu_thread_fn
> > (arg=arg@entry=0x2aa182103e0) at ../../accel/dummy-cpus.c:46
> > #3  0x000002aa16b22f5a in qemu_thread_start (args=<optimized out>) at
> > ../../util/qemu-thread-posix.c:541
> > #4  0x000003ff7e487aa8 in start_thread (arg=0x3ff5be1d910) at
> > pthread_create.c:463
> > #5  0x000003ff7e37a11e in thread_start () at
> > ../sysdeps/unix/sysv/linux/s390/s390-64/clone.S:65
> > 
> > Thread 3 (Thread 0x3ff608b4910 (LWP 60130)):
> > #0  0x000003ff7e36f1b0 in __GI___poll (fds=0x3ff540031f0, nfds=3,
> > timeout=<optimized out>) at ../sysdeps/unix/sysv/linux/poll.c:29
> > #1  0x000003ff7f9d2624 in  () at /usr/lib/s390x-linux-gnu/libglib-2.0.so.0
> > #2  0x000003ff7f9d2aa8 in g_main_loop_run () at
> > /usr/lib/s390x-linux-gnu/libglib-2.0.so.0
> > #3  0x000002aa1695ad26 in iothread_run
> > (opaque=opaque@entry=0x2aa17ea2b80) at ../../iothread.c:73
> > #4  0x000002aa16b22f5a in qemu_thread_start (args=<optimized out>) at
> > ../../util/qemu-thread-posix.c:541
> > #5  0x000003ff7e487aa8 in start_thread (arg=0x3ff608b4910) at
> > pthread_create.c:463
> > #6  0x000003ff7e37a11e in thread_start () at
> > ../sysdeps/unix/sysv/linux/s390/s390-64/clone.S:65
> > 
> > Thread 2 (Thread 0x3ff711b7910 (LWP 60129)):
> > #0  0x000003ff7e4911f6 in __lll_lock_wait
> > (futex=futex@entry=0x2aa17466bb8 <qemu_global_mutex>,
> > private=<optimized out>)
> >     at lowlevellock.c:46
> > #1  0x000003ff7e48a204 in __GI___pthread_mutex_lock
> > (mutex=mutex@entry=0x2aa17466bb8 <qemu_global_mutex>)
> >     at ../nptl/pthread_mutex_lock.c:80
> > #2  0x000002aa16b23116 in qemu_mutex_lock_impl (mutex=0x2aa17466bb8
> > <qemu_global_mutex>, file=0x2aa170a07d8 "../../util/rcu.c",
> > line=<optimized out>) at ../../util/qemu-thread-posix.c:79
> > #3  0x000002aa168221c0 in qemu_mutex_lock_iothread_impl
> > (file=file@entry=0x2aa170a07d8 "../../util/rcu.c",
> > line=line@entry=266)
> >     at ../../softmmu/cpus.c:493
> > #4  0x000002aa16b4c8aa in call_rcu_thread (opaque=opaque@entry=0x0) at
> > ../../util/rcu.c:266
> > #5  0x000002aa16b22f5a in qemu_thread_start (args=<optimized out>) at
> > ../../util/qemu-thread-posix.c:541
> > #6  0x000003ff7e487aa8 in start_thread (arg=0x3ff711b7910) at
> > pthread_create.c:463
> > #7  0x000003ff7e37a11e in thread_start () at
> > ../sysdeps/unix/sysv/linux/s390/s390-64/clone.S:65
> > 
> > Thread 1 (Thread 0x3ff81035470 (LWP 60123)):
> > #0  0x000003ff7e36f1b0 in __GI___poll (fds=0x2aa18147da0, nfds=2,
> > timeout=<optimized out>) at ../sysdeps/unix/sysv/linux/poll.c:29
> > #1  0x000003ff7f9d2624 in  () at /usr/lib/s390x-linux-gnu/libglib-2.0.so.0
> > #2  0x000003ff7f9d2aa8 in g_main_loop_run () at
> > /usr/lib/s390x-linux-gnu/libglib-2.0.so.0
> > #3  0x000002aa169104de in vhost_user_read
> > (dev=dev@entry=0x2aa18f7afc8, msg=msg@entry=0x3ffc167ddfc)
> >     at ../../hw/virtio/vhost-user.c:402
> > #4  0x000002aa1691186e in vhost_user_get_u64
> > (dev=dev@entry=0x2aa18f7afc8, request=request@entry=1,
> > u64=u64@entry=0x3ffc167e138)
> >     at ../../hw/virtio/vhost-user.c:1334
> > #5  0x000002aa16913388 in vhost_user_get_features
> > (features=0x3ffc167e138, dev=0x2aa18f7afc8) at
> > ../../hw/virtio/vhost-user.c:1356
> > #6  0x000002aa16913388 in vhost_user_backend_init (dev=0x2aa18f7afc8,
> > opaque=0x2aa18f7b240, errp=0x3ffc167e470)
> >     at ../../hw/virtio/vhost-user.c:1877
> > #7  0x000002aa1684030c in vhost_dev_init
> > (hdev=hdev@entry=0x2aa18f7afc8, opaque=opaque@entry=0x2aa18f7b240,
> > backend_type=backend_type@entry=VHOST_BACKEND_TYPE_USER,
> > busyloop_timeout=busyloop_timeout@entry=0,
> > errp=errp@entry=0x3ffc167e470)
> >     at ../../hw/virtio/vhost.c:1302
> > #8  0x000002aa168be742 in vhost_user_blk_connect
> > (dev=dev@entry=0x2aa18f7ad78, errp=errp@entry=0x3ffc167e470)
> >     at ../../hw/block/vhost-user-blk.c:339
> > #9  0x000002aa168bec44 in vhost_user_blk_realize_connect
> > (errp=0x3ffc167e470, s=0x2aa18f7ad78) at
> > ../../hw/block/vhost-user-blk.c:440
> > #10 0x000002aa168bec44 in vhost_user_blk_device_realize
> > (dev=0x2aa18f7ad78, errp=0x3ffc167e470)
> >     at ../../hw/block/vhost-user-blk.c:513
> > #11 0x000002aa16819e78 in virtio_device_realize (dev=0x2aa18f7ad78,
> > errp=0x3ffc167e530) at ../../hw/virtio/virtio.c:3659
> > #12 0x000002aa169fcc50 in device_set_realized (obj=<optimized out>,
> > value=<optimized out>, errp=0x3ffc167e690)
> >     at ../../hw/core/qdev.c:761
> > #13 0x000002aa169229ba in property_set_bool
> > (obj=obj@entry=0x2aa18f7ad78, v=v@entry=
> >     0x2aa18fc41e0, name=name@entry=0x2aa16ccfd74 "realized",
> > opaque=0x2aa17f2a7a0, errp=errp@entry=0x3ffc167e690)
> >     at ../../qom/object.c:2258
> > #14 0x000002aa16925534 in object_property_set
> > (obj=obj@entry=0x2aa18f7ad78, name=name@entry=0x2aa16ccfd74
> > "realized", v=v@entry=
> >     0x2aa18fc41e0, errp=errp@entry=0x3ffc167e980) at ../../qom/object.c:1403
> > #15 0x000002aa1692229c in object_property_set_qobject
> > (obj=obj@entry=0x2aa18f7ad78, name=name@entry=0x2aa16ccfd74
> > "realized", value=value@entry=0x2aa18fc4120,
> > errp=errp@entry=0x3ffc167e980) at ../../qom/qom-qobject.c:28
> > #16 0x000002aa169257e2 in object_property_set_bool (obj=0x2aa18f7ad78,
> > name=0x2aa16ccfd74 "realized", value=<optimized out>,
> > errp=0x3ffc167e980) at ../../qom/object.c:1473
> > #17 0x000002aa1677e9c2 in virtio_pci_realize (pci_dev=0x2aa18f72b80,
> > errp=0x3ffc167e980) at ../../hw/virtio/virtio-pci.c:1907
> > #18 0x000002aa165dfc48 in pci_qdev_realize (qdev=0x2aa18f72b80,
> > errp=<optimized out>) at ../../hw/pci/pci.c:2148
> > #19 0x000002aa169fcc50 in device_set_realized (obj=<optimized out>,
> > value=<optimized out>, errp=0x3ffc167ebe8)
> >     at ../../hw/core/qdev.c:761
> > #20 0x000002aa169229ba in property_set_bool
> > (obj=obj@entry=0x2aa18f72b80, v=v@entry=
> >     0x2aa18fbe450, name=name@entry=0x2aa16ccfd74 "realized",
> > opaque=0x2aa17f2a7a0, errp=errp@entry=0x3ffc167ebe8)
> >     at ../../qom/object.c:2258
> > #21 0x000002aa16925534 in object_property_set
> > (obj=obj@entry=0x2aa18f72b80, name=name@entry=0x2aa16ccfd74
> > "realized", v=v@entry=
> >     0x2aa18fbe450, errp=errp@entry=0x2aa17484fe0 <error_fatal>) at
> > ../../qom/object.c:1403
> > #22 0x000002aa1692229c in object_property_set_qobject
> > (obj=obj@entry=0x2aa18f72b80, name=name@entry=0x2aa16ccfd74
> > "realized", value=value@entry=0x2aa18fbe580,
> > errp=errp@entry=0x2aa17484fe0 <error_fatal>) at
> > ../../qom/qom-qobject.c:28
> > #23 0x000002aa169257e2 in object_property_set_bool (obj=0x2aa18f72b80,
> > name=name@entry=0x2aa16ccfd74 "realized", value=value@entry=true,
> > errp=0x2aa17484fe0 <error_fatal>, errp@entry=<error reading variable:
> > value has been optimized out>) at ../../qom/object.c:1473
> > #24 0x000002aa169fb87e in qdev_realize (dev=<optimized out>,
> > bus=bus@entry=0x2aa18384200, errp=<error reading variable: value has
> > been optimized out>) at ../../hw/core/qdev.c:389
> > #25 0x000002aa165f1c6c in qdev_device_add (opts=<optimized out>,
> > errp=<optimized out>, errp@entry=0x2aa17484fe0 <error_fatal>)
> >     at ../../softmmu/qdev-monitor.c:673
> > #26 0x000002aa168b2086 in device_init_func (opaque=<optimized out>,
> > opts=<optimized out>, errp=0x2aa17484fe0 <error_fatal>)
> >     at ../../softmmu/vl.c:1187
> > #27 0x000002aa16b2b906 in qemu_opts_foreach (list=<optimized out>,
> > func=func@entry=0x2aa168b2068 <device_init_func>,
> > opaque=opaque@entry=0x0, errp=0x2aa17484fe0 <error_fatal>) at
> > ../../util/qemu-option.c:1135
> > #28 0x000002aa168b5046 in qemu_create_cli_devices () at 
> > ../../softmmu/vl.c:2645
> > #29 0x000002aa168b5046 in qmp_x_exit_preconfig (errp=<optimized out>)
> > at ../../softmmu/vl.c:2693
> > #30 0x000002aa168b83ce in qemu_init (argc=<optimized out>,
> > argv=<optimized out>, envp=<optimized out>) at ../../softmmu/vl.c:3713
> > #31 0x000002aa1654f6da in main (argc=<optimized out>, argv=<optimized
> > out>, envp=<optimized out>) at ../../softmmu/main.c:49
> > 
> > 
> > Backtrace, qos-test:
> > 
> > Thread 2 (Thread 0x3ff9de7f910 (LWP 59555)):
> > #0  syscall () at ../sysdeps/unix/sysv/linux/s390/s390-64/syscall.S:53
> > #1  0x000002aa20c36a54 in qemu_futex_wait (val=<optimized out>,
> > f=<optimized out>) at /home/ubuntu/qemu/include/qemu/futex.h:29
> > #2  qemu_event_wait (ev=ev@entry=0x2aa20cdc3a0 <rcu_call_ready_event>)
> > at ../../util/qemu-thread-posix.c:480
> > #3  0x000002aa20c4efa4 in call_rcu_thread (opaque=opaque@entry=0x0) at
> > ../../util/rcu.c:258
> > #4  0x000002aa20c35a6a in qemu_thread_start (args=<optimized out>) at
> > ../../util/qemu-thread-posix.c:541
> > #5  0x000003ff9e887aa8 in start_thread (arg=0x3ff9de7f910) at
> > pthread_create.c:463
> > #6  0x000003ff9e77a11e in thread_start () at
> > ../sysdeps/unix/sysv/linux/s390/s390-64/clone.S:65
> > 
> > Thread 1 (Thread 0x3ff9eef0940 (LWP 59553)):
> > #0  0x000003ff9e89165a in __libc_read (fd=<optimized out>,
> > buf=buf@entry=0x3ffc10fd3e0, nbytes=nbytes@entry=1024)
> >     at ../sysdeps/unix/sysv/linux/read.c:27
> > #1  0x000002aa20bdee7a in read (__nbytes=1024, __buf=0x3ffc10fd3e0,
> > __fd=<optimized out>)
> >     at /usr/include/s390x-linux-gnu/bits/unistd.h:44
> > #2  qtest_client_socket_recv_line (s=0x2aa22379fc0) at
> > ../../tests/qtest/libqtest.c:494
> > #3  0x000002aa20bdf032 in qtest_rsp_args (s=s@entry=0x2aa22379fc0,
> > expected_args=expected_args@entry=1)
> >     at ../../tests/qtest/libqtest.c:521
> > #4  0x000002aa20bdf6f2 in qtest_query_target_endianness
> > (s=0x2aa22379fc0) at ../../tests/qtest/libqtest.c:570
> > #5  0x000002aa20be0312 in qtest_init_without_qmp_handshake
> > (extra_args=<optimized out>) at ../../tests/qtest/libqtest.c:332
> > #6  0x000002aa20be09e2 in qtest_init (extra_args=<optimized out>) at
> > ../../tests/qtest/libqtest.c:339
> > #7  0x000002aa20bc7b76 in qtest_start (
> >     args=0x2aa22389ef0 "-M pc  -device
> > vhost-user-blk-pci,id=drv0,chardev=char1,addr=4.0 -object
> > memory-backend-memfd,id=mem,size=256M,share=on  -M memory-backend=mem
> > -m 256M -chardev socket,id=char1,path=/tmp/qtest-59553-so"...)
> >     at ../../tests/qtest/libqtest-single.h:29
> > #8  restart_qemu_or_continue (
> >     path=0x2aa22389ef0 "-M pc  -device
> > vhost-user-blk-pci,id=drv0,chardev=char1,addr=4.0 -object
> > memory-backend-memfd,id=mem,size=256M,share=on  -M memory-backend=mem
> > -m 256M -chardev socket,id=char1,path=/tmp/qtest-59553-so"...) at
> > ../../tests/qtest/qos-test.c:105
> > #9  run_one_test (arg=<optimized out>) at ../../tests/qtest/qos-test.c:178
> > #10 0x000003ff9eb7c70c in ?? () from 
> > /usr/lib/s390x-linux-gnu/libglib-2.0.so.0
> > #11 0x000003ff9eb7c648 in ?? () from 
> > /usr/lib/s390x-linux-gnu/libglib-2.0.so.0
> > #12 0x000003ff9eb7c648 in ?? () from 
> > /usr/lib/s390x-linux-gnu/libglib-2.0.so.0
> > #13 0x000003ff9eb7c648 in ?? () from 
> > /usr/lib/s390x-linux-gnu/libglib-2.0.so.0
> > #14 0x000003ff9eb7c648 in ?? () from 
> > /usr/lib/s390x-linux-gnu/libglib-2.0.so.0
> > #15 0x000003ff9eb7c648 in ?? () from 
> > /usr/lib/s390x-linux-gnu/libglib-2.0.so.0
> > #16 0x000003ff9eb7c648 in ?? () from 
> > /usr/lib/s390x-linux-gnu/libglib-2.0.so.0
> > #17 0x000003ff9eb7c648 in ?? () from 
> > /usr/lib/s390x-linux-gnu/libglib-2.0.so.0
> > #18 0x000003ff9eb7c648 in ?? () from 
> > /usr/lib/s390x-linux-gnu/libglib-2.0.so.0
> > #19 0x000003ff9eb7c8ee in g_test_run_suite () from
> > /usr/lib/s390x-linux-gnu/libglib-2.0.so.0
> > #20 0x000003ff9eb7c928 in g_test_run () from
> > /usr/lib/s390x-linux-gnu/libglib-2.0.so.0
> > #21 0x000002aa20bc6c9a in main (argc=<optimized out>, argv=<optimized
> > out>, envp=<optimized out>) at ../../tests/qtest/qos-test.c:338
> > 
> > Backtrace, qemu-storage-daemon:
> > 
> > Thread 2 (Thread 0x3ff951b7910 (LWP 60132)):
> > #0  syscall () at ../sysdeps/unix/sysv/linux/s390/s390-64/syscall.S:53
> > #1  0x000002aa0184fa6c in qemu_futex_wait (val=<optimized out>,
> > f=<optimized out>) at /home/ubuntu/qemu/include/qemu/futex.h:29
> > #2  qemu_event_wait (ev=ev@entry=0x2aa01971158 <rcu_call_ready_event>)
> > at ../../util/qemu-thread-posix.c:480
> > #3  0x000002aa0187498c in call_rcu_thread (opaque=opaque@entry=0x0) at
> > ../../util/rcu.c:258
> > #4  0x000002aa0184ea82 in qemu_thread_start (args=<optimized out>) at
> > ../../util/qemu-thread-posix.c:541
> > #5  0x000003ffa0507aa8 in start_thread (arg=0x3ff951b7910) at
> > pthread_create.c:463
> > #6  0x000003ffa03fa11e in thread_start () at
> > ../sysdeps/unix/sysv/linux/s390/s390-64/clone.S:65
> > 
> > Thread 1 (Thread 0x3ffa14590e0 (LWP 60122)):
> > #0  0x000003ffa03ef302 in __GI_ppoll (fds=0x2aa0332b3d0, nfds=5,
> > timeout=<optimized out>, timeout@entry=0x0,
> >     sigmask=sigmask@entry=0x0) at ../sysdeps/unix/sysv/linux/ppoll.c:39
> > #1  0x000002aa0185b054 in ppoll (__ss=0x0, __timeout=0x0,
> > __nfds=<optimized out>, __fds=<optimized out>)
> >     at /usr/include/s390x-linux-gnu/bits/poll2.h:77
> > #2  qemu_poll_ns (fds=<optimized out>, nfds=<optimized out>,
> > timeout=timeout@entry=-1) at ../../util/qemu-timer.c:336
> > #3  0x000002aa01851e48 in os_host_main_loop_wait (timeout=-1) at
> > ../../util/main-loop.c:250
> > #4  main_loop_wait (nonblocking=<optimized out>) at 
> > ../../util/main-loop.c:531
> > #5  0x000002aa01738dda in main (argc=<optimized out>,
> > argv=0x3ffd28feba8) at ../../storage-daemon/qemu-storage-daemon.c:345
> > 
> > 
> > thanks
> > -- PMM
> 
>