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

[Jiri Denemark]

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.

...
> (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