Re: [libvirt] [PATCH 3/3] hold an extra reference while handling watchdog event

On Wed, Mar 30, 2011 at 12:34:49PM +0800, Wen Congyang wrote: > If the domain is not persistent, and qemu quited unexpectedly before > calling processWatchdogEvent(), vm will be freed and the function > processWatchdogEvent() will be dangerous. > > --- > src/qemu/qemu_driver.c | 10 ++++++---- > src/qemu/qemu_process.c | 4 ++++ > 2 files changed, 10 insertions(+), 4 deletions(-) > > diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c > index d79d61b..c9c681f 100644 > --- a/src/qemu/qemu_driver.c > +++ b/src/qemu/qemu_driver.c > @@ -2443,15 +2443,17 @@ static void processWatchdogEvent(void *data, void *opaque) > } > > endjob: > - if (qemuDomainObjEndJob(wdEvent->vm) == 0) > - wdEvent->vm = NULL; > + /* Safe to ignore value since ref count was incremented in > + * qemuProcessHandleWatchdog(). > + */ > + ignore_value(qemuDomainObjEndJob(wdEvent->vm)); > > unlock: > - if (wdEvent->vm) > - virDomainObjUnlock(wdEvent->vm); > qemuDriverUnlock(driver); > > cleanup: > + if (virDomainObjUnref(wdEvent->vm) > 0) > + virDomainObjUnlock(wdEvent->vm); These two lines should be protected by qemu driver lock.

> VIR_FREE(wdEvent); > } > > diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c > index e31e1b4..cd8c726 100644 > --- a/src/qemu/qemu_process.c > +++ b/src/qemu/qemu_process.c > @@ -426,6 +426,10 @@ qemuProcessHandleWatchdog(qemuMonitorPtr mon ATTRIBUTE_UNUSED, > if (VIR_ALLOC(wdEvent) == 0) { > wdEvent->action = VIR_DOMAIN_WATCHDOG_ACTION_DUMP; > wdEvent->vm = vm; > + /* Hold an extra reference because we can't allow 'vm' to be > + * deleted before handling watchdog event is finished. > + */ > + virDomainObjRef(vm); > ignore_value(virThreadPoolSendJob(driver->workerPool, wdEvent)); > } else > virReportOOMError(); > -- > 1.7.1