Re: [libvirt PATCH 3/3] qemu: Make qemuMigrationSrcCancel optionally synchronous

On Thu, Sep 01, 2022 at 14:47:41 +0200, Jiri Denemark wrote: > We have always considered "migrate_cancel" QMP command to return after > successfully cancelling the migration. But this is no longer true (to be > honest I'm not sure it ever was) as it just changes the migration state > to "cancelling". In most cases the migration is canceled pretty quickly > and we don't really notice anything, but sometimes it takes so long we > even get to clearing migration capabilities before the migration is > actually canceled, which fails as capabilities can only be changed when > no migration is running. So to avoid this issue, we can wait for the > migration to be really canceled after sending migrate_cancel. The only > place where we don't need synchronous behavior is when we're cancelling > migration on user's request while it is actively watched by another > thread. > > https://bugzilla.redhat.com/show_bug.cgi?id=2114866 > > Signed-off-by: Jiri Denemark <jdenemar(a)redhat.com&gt; > --- > src/qemu/qemu_driver.c | 2 +- > src/qemu/qemu_migration.c | 45 +++++++++++++++++++++++++++++++++++---- > src/qemu/qemu_migration.h | 3 ++- > src/qemu/qemu_process.c | 2 +- > 4 files changed, 45 insertions(+), 7 deletions(-) [...] > int > qemuMigrationSrcCancel(virDomainObj *vm, > - virDomainAsyncJob asyncJob) > + virDomainAsyncJob asyncJob, > + bool wait) > { > qemuDomainObjPrivate *priv = vm->privateData; > > @@ -4625,6 +4653,15 @@ qemuMigrationSrcCancel(virDomainObj *vm, > qemuMonitorMigrateCancel(priv->mon); > qemuDomainObjExitMonitor(vm); > > + if (virDomainObjIsActive(vm) && wait) { Is the call to virDomainObjIsActive() necessary here? IIUC the domain shutdown code is always executed in a way to make sure that waiting threads are always woken. > + VIR_DEBUG("Waiting for migration to be canceled"); > + > + while (!qemuMigrationSrcIsCanceled(vm)) { > + if (qemuDomainObjWait(vm) < 0) So here if the VM would crash before we wait we'd report success and if it crashed during our wait we'll report failure, which seems weird too.