Re: [libvirt] [PATCH 3/6] use virObject to manage reference-count of virDomainObj
On Tue, Apr 12, 2011 at 06:22:12PM +0800, Wen Congyang wrote:
At 04/12/2011 01:51 PM, Hu Tao Write:
> Sorry, I unexpectedly deleted text body.
>
> I changed the code like this:
>
> diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
> index c2a1f9a..8aad0b3 100644
> --- a/src/qemu/qemu_domain.c
> +++ b/src/qemu/qemu_domain.c
> @@ -514,7 +514,10 @@ int qemuDomainObjBeginJobWithDriver(struct qemud_driver
*driver,
> else
> virReportSystemError(errno,
> "%s", _("cannot acquire job
mutex"));
> + virDomainObjUnlock(obj);
> qemuDriverLock(driver);
> + virDomainObjLock(obj);
We lock qemu_driver and vm as the folling steps:
1. lock qemu_driver
2. lock vm
We try to lock qemu_driver while holding the vm's lock.
OOps, it will cause the libvirtd deadlock.(I can reproduce this bug by your script)
> + virDomainObjUnref(obj);
We have unref it, so do not unref it again.
Didn't see there is already a call to virDomainObjUnref. the patch
should be:
From 712883d0151222a276f777f473d96aa23ad5d9d6 Mon Sep 17 00:00:00 2001
From: Hu Tao <hutao(a)cn.fujitsu.com>
Date: Tue, 12 Apr 2011 18:29:27 +0800
Subject: [PATCH] qemu: fix a dead-lock problem
In qemuDomainObjBeginJobWithDriver, when virCondWaitUntil timeouts,
the function tries to call qemuDriverLock with virDomainObj locked,
this causes the dead-lock problem. This patch fixes this.
---
src/qemu/qemu_domain.c | 6 ++++--
1 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index c2a1f9a..a947b4e 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -506,15 +506,17 @@ int qemuDomainObjBeginJobWithDriver(struct qemud_driver *driver,
while (priv->jobActive) {
if (virCondWaitUntil(&priv->jobCond, &obj->lock, then) < 0) {
- /* Safe to ignore value since ref count was incremented above */
- ignore_value(virDomainObjUnref(obj));
if (errno == ETIMEDOUT)
qemuReportError(VIR_ERR_OPERATION_TIMEOUT,
"%s", _("cannot acquire state change
lock"));
else
virReportSystemError(errno,
"%s", _("cannot acquire job
mutex"));
+ virDomainObjUnlock(obj);
qemuDriverLock(driver);
+ virDomainObjLock(obj);
+ /* Safe to ignore value since ref count was incremented above */
+ ignore_value(virDomainObjUnref(obj));
return -1;
}
}
--
1.7.3.1