Re: [Qemu-devel] Aborts in iotest 169

[Vladimir Sementsov-Ogievskiy]

24.01.2019 13:10, Dr. David Alan Gilbert wrote:
> * Vladimir Sementsov-Ogievskiy (address@hidden) wrote:
>> 24.01.2019 12:29, Vladimir Sementsov-Ogievskiy wrote:
>>> 23.01.2019 18:48, Max Reitz wrote:
>>>> Hi,
>>>>
>>>> When running 169 in parallel (e.g. like so:
>>>>
>>>> $ while TEST_DIR=/tmp/t0 ./check -T -qcow2 169; do; done
>>>> $ while TEST_DIR=/tmp/t1 ./check -T -qcow2 169; do; done
>>>> $ while TEST_DIR=/tmp/t2 ./check -T -qcow2 169; do; done
>>>> $ while TEST_DIR=/tmp/t3 ./check -T -qcow2 169; do; done
>>>>
>>>> in four different shells), I get aborts:
>>>>
>>>> (Often I get segfaults, but that's because of
>>>> http://lists.nongnu.org/archive/html/qemu-devel/2018-12/msg05579.html --
>>>> feel free to apply the attached patch to make them go away)
>>>>
>>>>
>>>> WARNING:qemu:qemu received signal 6:
>>>> build/tests/qemu-iotests/../../x86_64-softmmu/qemu-system-x86_64
>>>> -chardev socket,id=mon,path=/tmp/t0/tmpbX30XU/qemua-25745-monitor.sock
>>>> -mon chardev=mon,mode=control -display none -vga none -qtest
>>>> unix:path=/tmp/t0/qemua-25745-qtest.sock -machine accel=qtest
>>>> -nodefaults -machine accel=qtest -drive
>>>> if=virtio,id=drive0,file=/tmp/t0/disk_a,format=qcow2,cache=writeback
>>>> .................E..
>>>> ======================================================================
>>>> ERROR:
>>>> test_do_test_migration_resume_source_not_persistent__not_migbitmap
>>>> (__main__.TestDirtyBitmapMigration)
>>>> ----------------------------------------------------------------------
>>>> Traceback (most recent call last):
>>>>     File "169", line 206, in <lambda>
>>>>       setattr(klass, 'test_' + method + name, lambda self: mc(self))
>>>>     File "169", line 113, in do_test_migration_resume_source
>>>>       self.check_bitmap(self.vm_a, sha256)
>>>>     File "169", line 72, in check_bitmap
>>>>       node='drive0', name='bitmap0')
>>>>     File "tests/qemu-iotests/../../scripts/qemu.py", line 369, in qmp
>>>>       return self._qmp.cmd(cmd, args=qmp_args)
>>>>     File "tests/qemu-iotests/../../scripts/qmp/qmp.py", line 191, in cmd
>>>>       return self.cmd_obj(qmp_cmd)
>>>>     File "tests/qemu-iotests/../../scripts/qmp/qmp.py", line 174, in 
>>>> cmd_obj
>>>>       resp = self.__json_read()
>>>>     File "tests/qemu-iotests/../../scripts/qmp/qmp.py", line 82, in
>>>> __json_read
>>>>       data = self.__sockfile.readline()
>>>>     File "/usr/lib64/python2.7/socket.py", line 451, in readline
>>>>       data = self._sock.recv(self._rbufsize)
>>>> error: [Errno 104] Connection reset by peer
>>>>
>>>> ----------------------------------------------------------------------
>>>> Ran 20 tests
>>>>
>>>> FAILED (errors=1)
>>>>
>>>>
>>>> Or:
>>>>
>>>> WARNING:qemu:qemu received signal 6:
>>>> build/tests/qemu-iotests/../../x86_64-softmmu/qemu-system-x86_64
>>>> -chardev socket,id=mon,path=/tmp/t3/tmp0pllWD/qemua-3445-monitor.sock
>>>> -mon chardev=mon,mode=control -display none -vga none -qtest
>>>> unix:path=/tmp/t3/qemua-3445-qtest.sock -machine accel=qtest -nodefaults
>>>> -machine accel=qtest -drive
>>>> if=virtio,id=drive0,file=/tmp/t3/disk_a,format=qcow2,cache=writeback
>>>> WARNING:qemu:qemu received signal 6:
>>>> build/tests/qemu-iotests/../../x86_64-softmmu/qemu-system-x86_64
>>>> -chardev socket,id=mon,path=/tmp/t3/tmp0pllWD/qemua-3445-monitor.sock
>>>> -mon chardev=mon,mode=control -display none -vga none -qtest
>>>> unix:path=/tmp/t3/qemua-3445-qtest.sock -machine accel=qtest -nodefaults
>>>> -machine accel=qtest -drive
>>>> if=virtio,id=drive0,file=/tmp/t3/disk_a,format=qcow2,cache=writeback
>>>>
>>>> ...................F
>>>> ======================================================================
>>>> FAIL: test_do_test_migration_resume_source_persistent__not_migbitmap
>>>> (__main__.TestDirtyBitmapMigration)
>>>> ----------------------------------------------------------------------
>>>> Traceback (most recent call last):
>>>>     File "169", line 206, in <lambda>
>>>>       setattr(klass, 'test_' + method + name, lambda self: mc(self))
>>>>     File "169", line 125, in do_test_migration_resume_source
>>>>       self.assertEqual(log, '')
>>>> AssertionError: "qemu-system-x86_64: invalid runstate transition:
>>>> 'running' -> 'postmigrate'\n" != ''
>>>>
>>>> ----------------------------------------------------------------------
>>>> Ran 20 tests
>>>>
>>>> FAILED (failures=1)
>>>>
>>>>
>>>> The backtrace always goes like this:
>>>>
>>>> (gdb) bt
>>>> #0  0x00007f0acf5cc53f in raise () at /lib64/libc.so.6
>>>> #1  0x00007f0acf5b6895 in abort () at /lib64/libc.so.6
>>>> #2  0x000055a46ebbb1a6 in runstate_set (new_state=RUN_STATE_POSTMIGRATE)
>>>> at vl.c:742
>>>> #3  0x000055a46ebbb1a6 in runstate_set
>>>> (address@hidden) at vl.c:730
>>>> #4  0x000055a46ed39129 in migration_iteration_finish (s=0x55a4708be000)
>>>> at migration/migration.c:2972
>>>> #5  0x000055a46ed39129 in migration_thread
>>>> (address@hidden) at migration/migration.c:3130
>>>> #6  0x000055a46eea665a in qemu_thread_start (args=<optimized out>) at
>>>> util/qemu-thread-posix.c:502
>>>>
>>>>
>>>> #7  0x00007f0acf76258e in start_thread () at /lib64/libpthread.so.0
>>>> #8  0x00007f0acf6916a3 in clone () at /lib64/libc.so.6
>>>> (gdb) frame 2
>>>> #2  0x000055a46ebbb1a6 in runstate_set (new_state=RUN_STATE_POSTMIGRATE)
>>>> at vl.c:742
>>>> 742             abort();
>>>> (gdb) print current_run_state
>>>> $1 = RUN_STATE_RUNNING
>>>>
>>>>
>>>> Neither of migration or runstates are my strong suite, so I thought I'd
>>>> report it before diving into it.
>>>>
>>>> Max
>>>>
>>>
>>> [...]
>>> address@hidden:migrate_set_state new state active
>>> address@hidden:migration_thread_setup_complete
>>> address@hidden:migrate_transferred transferred 985298 time_spent 100 
>>> bandwidth 9852 max_size 2955894
>>> address@hidden:migration_bitmap_sync_start
>>> address@hidden:migration_bitmap_sync_end dirty_pages 32898
>>> address@hidden:migration_thread_low_pending 2048
>>> migration_completion
>>> address@hidden:runstate_set current_state 9 new_state 7
>>> address@hidden:migration_bitmap_sync_start
>>> address@hidden:migration_bitmap_sync_end dirty_pages 32898
>>> address@hidden:migrate_global_state_pre_save saved state: running
>>> [1] address@hidden:migrate_set_state new state completed
>>> address@hidden:handle_qmp_command mon 0x55aebef99830 req: {"execute": 
>>> "x-debug-block-dirty-bitmap-sha256", "arguments": {"name": "bitmap0", 
>>> "node": "drive0"}}
>>> address@hidden:migration_thread_after_loop
>>> [2] address@hidden:handle_qmp_command mon 0x55aebef99830 req: {"execute": 
>>> "cont"}
>>> address@hidden:runstate_set current_state 7 new_state 9
>>> qemu-system-x86_64: invalid runstate transition: 'running' -> 'postmigrate'
>>>
>>>
>>> Aha, so, in test we wait for MIGRATION COMPLETED [1] and run qmp_cont [2] 
>>> and go to RUNNING.
>>> then in migration thread we go to migration_iteration_finish() and fail to 
>>> go to POSTMIGRATE.
>>> (note, that this testcase is about resuming source after migration)
>>>
>>> So, fix for test may be additionally wait for POSTMIGRATE, not only for 
>>> MIGRATION COMPLETION.
>>>
>>> But how to fix Qemu not to crash? May be, forbid some transitions 
>>> (FINISH_MIGRATE -> RUNNING),
>>>    or at least error-out qmp_cont if runstate is  FINISH_MIGRATE?
>>>
>>>
>>>
>>
>>
>> Ok, this seems to fix test for me:
>>
>> diff --git a/tests/qemu-iotests/169 b/tests/qemu-iotests/169
>> index 527aebd0cb..dd98168c8d 100755
>> --- a/tests/qemu-iotests/169
>> +++ b/tests/qemu-iotests/169
>> @@ -102,6 +102,10 @@ class TestDirtyBitmapMigration(iotests.QMPTestCase):
>>                event = self.vm_a.event_wait('MIGRATION')
>>                if event['data']['status'] == 'completed':
>>                    break
>> +        while True:
>> +            result = self.vm_a.qmp('query-status')
>> +            if (result['return']['status'] == 'postmigrate'):
>> +                break
> 
> Hmm; I can see that it might help; although I still can't quite see
> how the bad transition that was reported can have happened.
> 

It can be assumed from my trace above:

1. migration thread do migratioN_completion and goes to 
RUN_STATE_FINISH_MIGRATE through vm_stop_force_state(RUN_STATE_FINISH_MIGRATE)
2. migration_completion do
         migrate_set_state(&s->state, current_active_state,
                             MIGRATION_STATUS_COMPLETED);
    and MIGRATION COMPLETED event is reported, so
3. 169 iotest gets event, and think that all is done about migration. And it 
call qmp_cont
4. qmp_cont do transition from RUN_STATE_FINISH_MIGRATE to RUN_STATE_RUNNING
5. migration thread goes to migration_iteration_finish and do invalid transition


> 
>>            # test that bitmap is still here
>>            removed = (not migrate_bitmaps) and persistent
>>
>> -
>>
>>
>> And this is the full diff of the test I used, to skip checking log (as I 
>> enabled traces) and to skip all other test-cases:
>>
>> (hmm, we definitely need simple way to run one test case from test, without 
>> editing it)
>>
>> diff --git a/tests/qemu-iotests/169 b/tests/qemu-iotests/169
>> index 527aebd0cb..dd98168c8d 100755
>> --- a/tests/qemu-iotests/169
>> +++ b/tests/qemu-iotests/169
>> @@ -102,6 +102,10 @@ class TestDirtyBitmapMigration(iotests.QMPTestCase):
>>                event = self.vm_a.event_wait('MIGRATION')
>>                if event['data']['status'] == 'completed':
>>                    break
>> +        while True:
>> +            result = self.vm_a.qmp('query-status')
>> +            if (result['return']['status'] == 'postmigrate'):
>> +                break
>>
>>            # test that bitmap is still here
>>            removed = (not migrate_bitmaps) and persistent
>> @@ -117,12 +121,12 @@ class TestDirtyBitmapMigration(iotests.QMPTestCase):
>>
>>            # catch 'Could not reopen qcow2 layer: Bitmap already exists'
>>            # possible error
>> -        log = self.vm_a.get_log()
>> -        log = re.sub(r'^\[I \d+\.\d+\] OPENED\n', '', log)
>> -        log = re.sub(r'^(wrote .* bytes at offset 
>> .*\n.*KiB.*ops.*sec.*\n){3}',
>> -                     '', log)
>> -        log = re.sub(r'\[I \+\d+\.\d+\] CLOSED\n?$', '', log)
>> -        self.assertEqual(log, '')
>> +        #log = self.vm_a.get_log()
>> +        #log = re.sub(r'^\[I \d+\.\d+\] OPENED\n', '', log)
>> +        #log = re.sub(r'^(wrote .* bytes at offset 
>> .*\n.*KiB.*ops.*sec.*\n){3}',
>> +                     #'', log)
>> +        #log = re.sub(r'\[I \+\d+\.\d+\] CLOSED\n?$', '', log)
>> +        #self.assertEqual(log, '')
>>
>>            # test that bitmap is still persistent
>>            self.vm_a.launch()
>> @@ -211,14 +215,16 @@ for cmb in list(itertools.product((True, False), 
>> repeat=4)):
>>        name += '_online' if cmb[2] else '_offline'
>>        name += '_shared' if cmb[3] else '_nonshared'
>>
>> -    inject_test_case(TestDirtyBitmapMigration, name, 'do_test_migration',
>> +    if False:
>> +        inject_test_case(TestDirtyBitmapMigration, name, 
>> 'do_test_migration',
>>                         *list(cmb))
>>
>>    for cmb in list(itertools.product((True, False), repeat=2)):
>>        name = ('_' if cmb[0] else '_not_') + 'persistent_'
>>        name += ('_' if cmb[1] else '_not_') + 'migbitmap'
>>
>> -    inject_test_case(TestDirtyBitmapMigration, name,
>> +    if name == '_persistent__migbitmap':
>> +        inject_test_case(TestDirtyBitmapMigration, name,
>>                         'do_test_migration_resume_source', *list(cmb))
>>
>>    if __name__ == '__main__':
>> diff --git a/tests/qemu-iotests/169.out b/tests/qemu-iotests/169.out
>> index 3a89159833..ae1213e6f8 100644
>> --- a/tests/qemu-iotests/169.out
>> +++ b/tests/qemu-iotests/169.out
>> @@ -1,5 +1,5 @@
>> -....................
>> +.
>>    ----------------------------------------------------------------------
>> -Ran 20 tests
>> +Ran 1 tests
>>
>>    OK
>>
>>
>>
>> -- 
>> Best regards,
>> Vladimir
> --
> Dr. David Alan Gilbert / address@hidden / Manchester, UK
> 


-- 
Best regards,
Vladimir