Re: [PATCH] qemu: Remove double unlock for domains

[Martin Kletzander <mkletzan@xxxxxxxxxx>]

On Mon, Aug 03, 2015 at 04:00:32PM +0200, Martin Kletzander wrote:
> On Mon, Aug 03, 2015 at 09:21:51AM -0400, John Ferlan wrote:
> > On 07/15/2015 03:17 AM, Martin Kletzander wrote:
> > > The virDomainObjListRemove() function unlocks a domain that it's given
> > > due to legacy code.  And because of that code, which should be
> > > refactored, that last virObjectUnlock() cannot be just removed.  So
> > > instead, lock it right back for qemu for now.  All calls to
> > > qemuDomainRemoveInactive() are followed by code that unlocks the domain
> > > again, plus the domain should be locked during qemuDomainObjEndJob(), so
> > > the right place to lock it is right after virDomainObjListRemove().
> >
> > Looked through callers - seems qemuProcessHandleMonitorEOF may need a
> > tweak too as it skips around the virObjectUnlock(vm)
> >
> > My only other comment would be perhaps the entry comment into
> > qemuDomainRemoveInactive could use a tweak on the wording and some
> > additional text to indicate on exit it should still hold the lock (or
> > just move the blob you added... Perhaps an XXX to force a revisit in the
> > future based on your note above "which should be refactored"
> >
> > Not that anyone reads those anyway ;-)
> >
> > ACK with the double check on the *EOF function...
>
> Would it be enough if I squashed this in?

Sorry, incomplete diff, here's the proper one, it's cleaner and looks
better (and compiles):

diff --git i/src/qemu/qemu_domain.c w/src/qemu/qemu_domain.c
index d6d723112638..6ba8087c108b 100644
--- i/src/qemu/qemu_domain.c
+++ w/src/qemu/qemu_domain.c
@@ -2597,7 +2597,13 @@ qemuDomainRemoveInactive(virQEMUDriverPtr driver,
     * virDomainObjListRemove() leaves the domain unlocked so it can
     * be unref'd for other drivers that depend on that, but we still
     * need to reset a job and we have a reference from the API that
-     * called this function.  So we need to lock it back.
+     * called this function.  So we need to lock it back.  This is
+     * just a workaround for the qemu driver.
+     *
+     * XXX: Ideally, the global handling of domain objects and object
+     *      lists would be refactored so we don't need hacks like
+     *      this, but since that requires refactor of all drivers,
+     *      it's a work for another day.
     */
    virObjectLock(vm);
    virObjectUnref(cfg);
diff --git i/src/qemu/qemu_process.c w/src/qemu/qemu_process.c
index 5a9f97bc8921..505778ec2f05 100644
--- i/src/qemu/qemu_process.c
+++ w/src/qemu/qemu_process.c
@@ -295,12 +295,12 @@ qemuProcessHandleMonitorEOF(qemuMonitorPtr mon ATTRIBUTE_UNUSED,

    if (priv->beingDestroyed) {
        VIR_DEBUG("Domain is being destroyed, EOF is expected");
-        goto unlock;
+        goto cleanup;
    }

    if (!virDomainObjIsActive(vm)) {
        VIR_DEBUG("Domain %p is not active, ignoring EOF", vm);
-        goto unlock;
+        goto cleanup;
    }

    if (priv->monJSON && !priv->gotShutdown) {
@@ -323,15 +323,11 @@ qemuProcessHandleMonitorEOF(qemuMonitorPtr mon ATTRIBUTE_UNUSED,
    qemuProcessStop(driver, vm, stopReason, stopFlags);
    virDomainAuditStop(vm, auditReason);

-    if (!vm->persistent) {
+    if (!vm->persistent)
        qemuDomainRemoveInactive(driver, vm);
-        goto cleanup;
-    }
-
- unlock:
-    virObjectUnlock(vm);

 cleanup:
+    virObjectUnlock(vm);
    if (event)
        qemuDomainEventQueue(driver, event);
}
--

Martin

Attachment: signature.asc
Description: PGP signature

--
libvir-list mailing list
libvir-list@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/libvir-list