At 04/12/2011 06:40 PM, Daniel P. Berrange Write:
> On Tue, Apr 12, 2011 at 06:33:21PM +0800, Hu Tao wrote:
>> 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@xxxxxxxxxxxxxx>
>> 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;
>> }
>> }
>> --
>
> ACK
Thanks. Applied.
>
> Daniel
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