Il 22/08/2013 11:50, Asias He ha scritto:
> On Wed, Aug 21, 2013 at 10:16:02AM +0200, Paolo Bonzini wrote:
>> Il 21/08/2013 04:02, Asias He ha scritto:
>>> In block/gluster.c, we have
>>>
>>> gluster_finish_aiocb
>>> {
>>> if (retval != sizeof(acb)) {
>>> qemu_mutex_lock_iothread(); /* We are in gluster thread context */
>>> ...
>>> qemu_mutex_unlock_iothread();
>>> }
>>> }
>>>
>>> qemu tools, e.g. qemu-img, might race here because
>>> qemu_mutex_{lock,unlock}_iothread are a nop operation and
>>> gluster_finish_aiocb is in the gluster thread context.
>>>
>>> To fix, we introduce our own mutex for qemu tools.
>>>
>>> Signed-off-by: Asias He <as...@redhat.com>
>>> ---
>>> stubs/iothread-lock.c | 11 +++++++++++
>>> 1 file changed, 11 insertions(+)
>>>
>>> diff --git a/stubs/iothread-lock.c b/stubs/iothread-lock.c
>>> index 5d8aca1..d5c6dec 100644
>>> --- a/stubs/iothread-lock.c
>>> +++ b/stubs/iothread-lock.c
>>> @@ -1,10 +1,21 @@
>>> #include "qemu-common.h"
>>> #include "qemu/main-loop.h"
>>>
>>> +static QemuMutex qemu_tools_mutex;
>>> +static pthread_once_t qemu_tools_once = PTHREAD_ONCE_INIT;
>>
>> Doesn't work on Windows, but you can just add
>
> Hmm, Any reasons, why it does not work on Windows?
There are no pthreads on Windows.
There is an emulation library, but we're not using it.
>> __attribute__((__constructor__)) to qemu_tools_mutex_init.
>
> __attribute__((__constructor__)) works on Windows?
Yes, it is part of the runtime library's support for C++. We use it
already, see include/qemu/module.h.
Paolo
>> Paolo
>>
>>> +static void qemu_tools_mutex_init(void)
>>> +{
>>> + qemu_mutex_init(&qemu_tools_mutex);
>>> +}
>>> +
>>> void qemu_mutex_lock_iothread(void)
>>> {
>>> + pthread_once(&qemu_tools_once, qemu_tools_mutex_init);
>>> + qemu_mutex_lock(&qemu_tools_mutex);
>>> }
>>>
>>> void qemu_mutex_unlock_iothread(void)
>>> {
>>> + qemu_mutex_unlock(&qemu_tools_mutex);
>>> }
>>>
>>
>
