[libvirt] [PATCH v3 00/24] Add support for migration events

[John Ferlan]

On 06/10/2015 11:06 AM, Jiri Denemark wrote:
> On Wed, Jun 10, 2015 at 10:27:11 -0400, John Ferlan wrote:
>>
>>
>> On 06/10/2015 09:42 AM, Jiri Denemark wrote:
>>> QEMU will soon (patches are available on qemu-devel) get support for
>>> migration events which will finally allow us to get rid of polling
>>> query-migrate every 50ms. However, we first need to be able to wait for
>>> all events related to migration (migration status changes, block job
>>> events, async abort requests) at once. This series prepares the
>>> infrastructure and uses it to switch all polling loops in migration code
>>> to pthread_cond_wait.
>>>
>>> https://bugzilla.redhat.com/show_bug.cgi?id=1212077
>>>
>>> Version 3 (see individual patches for details):
>>> - most of the series has been ACKed in v2
>>> - "qemu: Use domain condition for synchronous block jobs" was split in 3
>>>   patches for easier review
>>> - minor changes requested in v2 review
>>>
>>> Version 2 (see individual patches for details):
>>> - rewritten using per-domain condition variable
>>> - enahnced to fully support the migration events
>>
>> Just ran this through my Coverity checker - only one issue
>>
>> RESOURCE_LEAK in qemuMigrationRun:
>>
>> 4235 	        if (qemuMigrationCheckJobStatus(driver, vm,
>> 4236 	                                        QEMU_ASYNC_JOB_MIGRATION_OUT) < 0)
>>
>> (4) Event if_end: 	End of if statement
>>
>> 4237 	            goto cancel;
>> 4238 	
>>
>> (5) Event open_fn: 	Returning handle opened by "accept".
>> (6) Event var_assign: 	Assigning: "fd" = handle returned from "accept(spec->dest.unix_socket.sock, __SOCKADDR_ARG({ .__sockaddr__ = NULL}), NULL)".
>> (7) Event cond_false: 	Condition "(fd = accept(spec->dest.unix_socket.sock, __SOCKADDR_ARG({ .__sockaddr__ = NULL}), NULL)) < 0", taking false branch
>> Also see events: 	[leaked_handle]
>>
>> 4239 	        while ((fd = accept(spec->dest.unix_socket.sock, NULL, NULL)) < 0) {
>> 4240 	            if (errno == EAGAIN || errno == EINTR)
>> 4241 	                continue;
> 
> Hmm, what an old and unused (except for some ancient QEMU versions) code
> path :-) However, this code is only executed if spec->destType ==
> MIGRATION_DEST_UNIX, which only happens in tunnelled migration path,
> which also sets spec.fwdType = MIGRATION_FWD_STREAM.
> 

Placing "sa_assert(spec->fwdType == MIGRATION_FWD_STREAM);" above the
while loop makes Coverity happy.

John
> ...
>> (28) Event cond_false: 	Condition "spec->fwdType != MIGRATION_FWD_DIRECT", taking false branch
>>
>> 4289 	    if (spec->fwdType != MIGRATION_FWD_DIRECT) {
>> 4290 	        if (iothread && qemuMigrationStopTunnel(iothread, ret < 0) < 0)
>> 4291 	            ret = -1;
>> 4292 	        VIR_FORCE_CLOSE(fd);
> 
> Which means "spec->fwdType != MIGRATION_FWD_DIRECT" will be true and fd
> will be correctly closed.
> 
> Jirka
>