Re: [Qemu-devel] [PATCH v4 6/7] qom: replace object property list with GHashTable

[Christian Borntraeger]

On 11/13/2015 07:14 PM, Andreas Färber wrote:
> Am 13.10.2015 um 14:37 schrieb Daniel P. Berrange:
>> From: Pavel Fedin <address@hidden>
>>
>> ARM GICv3 systems with large number of CPUs create lots of IRQ pins. Since
>> every pin is represented as a property, number of these properties becomes
>> very large. Every property add first makes sure there's no duplicates.
>> Traversing the list becomes very slow, therefore qemu initialization takes
>> significant time (several seconds for e. g. 16 CPUs).
>>
>> This patch replaces list with GHashTable, making lookup very fast. The only
>> drawback is that object_child_foreach() and object_child_foreach_recursive()
>> cannot modify their objects during traversal, since GHashTableIter does not
>> have modify-safe version. However, the code seems not to modify objects via
>> these functions.
>>
>> Signed-off-by: Daniel P. Berrange <address@hidden>
>> Signed-off-by: Pavel Fedin <address@hidden>
> 
> (note these seemed misordered)
> 
> I have queued things up to 6/7 on qom-next:
> https://github.com/afaerber/qemu-cpu/commits/qom-next
> 
> This patch didn't apply and I had to hand-apply one hunk (which I
> double-checked, but you never know).
> 
> Unfortunately I run into this test failure:
> 
> TEST: tests/device-introspect-test... (pid=4094)
>   /s390x/device/introspect/list:                                       OK
>   /s390x/device/introspect/none:                                       OK
>   /s390x/device/introspect/abstract:                                   OK
>   /s390x/device/introspect/concrete:
> (process:4102): GLib-CRITICAL **: g_hash_table_iter_next: assertion
> 'ri->version == ri->hash_table->version' failed
> 
> (process:4102): GLib-CRITICAL **: g_hash_table_iter_next: assertion
> 'ri->version == ri->hash_table->version' failed
> 
> (process:4102): GLib-CRITICAL **: iter_remove_or_steal: assertion
> 'ri->version == ri->hash_table->version' failed
> **
> ERROR:/home/andreas/QEMU/qemu/qom/object.c:867:object_unref: assertion
> failed: (obj->ref > 0)
> Broken pipe
> FAIL
> GTester: last random seed: R02S4fa2068506971129a7ebe2323dbe03b7
> (pid=4104)
> FAIL: tests/device-introspect-test
> TEST: tests/qom-test... (pid=4105)
>   /s390x/qom/s390-ccw-virtio-2.5:                                      OK
>   /s390x/qom/s390-ccw-virtio-2.4:                                      OK
>   /s390x/qom/none:                                                     OK
>   /s390x/qom/s390-virtio:
> WARNING
> The s390-virtio machine (non-ccw) is deprecated.
> It will be removed in 2.6. Please use s390-ccw-virtio
> OK
> PASS: tests/qom-test
> 
> Are you sure you tested all targets?
> Any hunch where this might stem from?
> 
> The below patch reveals that the ref count is 0. Might be just a symptom
> of the actual problem though.

A simpler reproducer is
s390x-softmmu/qemu-system-s390x  -device sclp,help
which fails with this patch and succeeds without.