[libvirt] 回复: [PATCH] qemu: snapshot: Fix libvirtd crash in snapshot-revert

-----邮件原件----- 发件人: Michal Privoznik <mprivozn(a)redhat.com&gt; 发送时间: 2019年12月13日 17:30 收件人: Peter Krempa <pkrempa(a)redhat.com>; Lin Ma <LMa(a)suse.com&gt; 抄送: libvir-list(a)redhat.com 主题: Re: [libvirt] [PATCH] qemu: snapshot: Fix libvirtd crash in snapshot-revert On 12/13/19 8:55 AM, Peter Krempa wrote: > On Fri, Dec 13, 2019 at 15:47:36 +0800, Lin Ma wrote: >> When reverting a running domain to a snapshot(active state), We need >> to use the FORCE flag for snapshot-revert if current domain >> configuration is different from the target domain configuration, and >> this will start a new qemu instance for the target domain. >> >> In this situation, if there is existing connection to the domain, say >> Spice or VNC through virt-manager, Then the libvirtd would crash >> during snapshot revert because: Both of snapshot revert worker and >> new worker job 'remoteDispatchDomainOpenGraphicsFd' are waiting for >> mon->msg->finished in qemuMonitorSend(), We know if IO process >> resulted in an error with a message, Libvirtd main thread calls qemuMonitorIO() to wakeup the waiter. >> Then mon->msg will be set to NULL in qemuMonitorSend() once the >> worker GraphicsFD is woken up, which causes snapshot revert worker >> dereferences this null pointer. > > [....] > >> Signed-off-by: Lin Ma <lma(a)suse.com&gt; >> --- >> src/qemu/qemu_monitor.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/src/qemu/qemu_monitor.c b/src/qemu/qemu_monitor.c index >> ea3e62dc8e..a8344e698b 100644 >> --- a/src/qemu/qemu_monitor.c >> +++ b/src/qemu/qemu_monitor.c >> @@ -994,7 +994,7 @@ qemuMonitorSend(qemuMonitorPtr mon, >> "mon=%p msg=%s fd=%d", >> mon, mon->msg->txBuffer, mon->msg->txFD); >> >> - while (!mon->msg->finished) { >> + while (mon->msg && !mon->msg->finished) { > > This fixes only the symptom. The actual problem is in handling of our > job state when restarting the qemu process: > > Please see the following patches which aim to fix the same problem: > > https://www.redhat.com/archives/libvir-list/2019-December/msg00663.htm > l In fact, I've pushed the patch yesterday: d75f865fb9 qemu: fix concurrency crash bug in snapshot revert Does it fix the problem you're seeing?