[libvirt] [PATCH] qemu: Double mutex unlock in qemuDomainModifyDeviceFlags

[Eric Blake]

On 01/17/2013 10:25 AM, Viktor Mihajlovski wrote:
> The driver mutex was unlocked in qemuDomainModifyDeviceFlags before
> entering qemuDomainObjBeginJobWithDriver where it will be unlocked once
> more leaving it in an undefined state. The result was that two
> threads were simultaneously looking up the domain hash table during
> multiple parallel device attach/detach operations.
> Luckily this triggered a virHashIterationError.
> 
> Signed-off-by: Viktor Mihajlovski <mihajlov at linux.vnet.ibm.com>
> ---
>  src/qemu/qemu_driver.c |    1 -
>  1 file changed, 1 deletion(-)

I tracked this down to commit 8c5d2ba; it looks like Michal encountered
a case of git botching a rebase when forward-porting a patch.  If you'll
look at that commit, we removed a qemuDriverUnlock() from one function
(qemuDomainSendKey), added it to another (qemuDomainModifyDeviceFlags),
neither in a pair; and neither matches the commit message mention of
DomainHasManagedSaveImage.  You only repaired one piece of the damage,
but missed the other damage, and we still haven't fixed the intended
function.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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