Re: [libvirt] [PATCH] Fix thread safety in LXC callback handling

From: "Daniel P. Berrange" <berrange(a)redhat.com&gt; Some of the LXC callbacks did not lock the virDomainObjPtr instance. This caused transient errors like error: Failed to start domain busy-mount error: cannot rename file '/var/run/libvirt/lxc/busy-mount.xml.new' as '/var/run/libvirt/lxc/busy-mount.xml': No such file or directory as 2 threads tried to update the status file concurrently Signed-off-by: Daniel P. Berrange <berrange(a)redhat.com&gt; --- src/lxc/lxc_process.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/src/lxc/lxc_process.c b/src/lxc/lxc_process.c index 670a032..39a6ea2 100644 --- a/src/lxc/lxc_process.c +++ b/src/lxc/lxc_process.c @@ -610,8 +610,13 @@ static void virLXCProcessMonitorExitNotify(virLXCMonitorPtr mon ATTRIBUTE_UNUSED virLXCMonitorExitStatus status, virDomainObjPtr vm) { + virLXCDriverPtr driver = lxc_driver; virLXCDomainObjPrivatePtr priv = vm->privateData; + lxcDriverLock(driver); + virObjectLock(vm); + lxcDriverUnlock(driver); + switch (status) { case VIR_LXC_MONITOR_EXIT_STATUS_SHUTDOWN: priv->stopReason = VIR_DOMAIN_EVENT_STOPPED_SHUTDOWN; @@ -629,6 +634,8 @@ static void virLXCProcessMonitorExitNotify(virLXCMonitorPtr mon ATTRIBUTE_UNUSED } VIR_DEBUG("Domain shutoff reason %d (from status %d)", priv->stopReason, status); + + virObjectUnlock(vm); } static int @@ -667,9 +674,15 @@ static void virLXCProcessMonitorInitNotify(virLXCMonitorPtr mon ATTRIBUTE_UNUSED pid_t initpid, virDomainObjPtr vm) { - virLXCDomainObjPrivatePtr priv = vm->privateData; + virLXCDriverPtr driver = lxc_driver; + virLXCDomainObjPrivatePtr priv; ino_t inode; + lxcDriverLock(driver); + virObjectLock(vm); + lxcDriverUnlock(driver); + + priv = vm->privateData; priv->initpid = initpid; if (virLXCProcessGetNsInode(initpid, "pid", &inode) < 0) { @@ -684,6 +697,8 @@ static void virLXCProcessMonitorInitNotify(virLXCMonitorPtr mon ATTRIBUTE_UNUSED if (virDomainSaveStatus(lxc_driver->xmlconf, lxc_driver->stateDir, vm) < 0) VIR_WARN("Cannot update XML with PID for LXC %s", vm->def->name); + + virObjectUnlock(vm); } static virLXCMonitorCallbacks monitorCallbacks = {