On 08/07/14 19:08, Paolo Bonzini wrote:
> Il 08/07/2014 17:59, Stefan Hajnoczi ha scritto:
>> I sent Christian an initial patch to fix this but now both threads are
>> stuck in rfifolock_lock() inside cond wait. That's very strange and
>> should never happen.
>
> I had this patch pending for 2.2:
>
> commit 6c81e31615c3cda5ea981a998ba8b1b8ed17de6f
> Author: Paolo Bonzini <pbonz...@redhat.com>
> Date: Mon Jul 7 10:39:49 2014 +0200
>
> iothread: do not rely on aio_poll(ctx, true) result to end a loop
>
> Currently, whenever aio_poll(ctx, true) has completed all pending
> work it returns true *and* the next call to aio_poll(ctx, true)
> will not block.
>
> This invariant has its roots in qemu_aio_flush()'s implementation
> as "while (qemu_aio_wait()) {}". However, qemu_aio_flush() does
> not exist anymore and bdrv_drain_all() is implemented differently;
> and this invariant is complicated to maintain and subtly different
> from the return value of GMainLoop's g_main_context_iteration.
>
> All calls to aio_poll(ctx, true) except one are guarded by a
> while() loop checking for a request to be incomplete, or a
> BlockDriverState to be idle. Modify that one exception in
> iothread.c.
>
> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
The hangs are gone. Looks like 2.1 material now...
Acked-by: Christian Borntraeger <borntrae...@de.ibm.com>
Tested-by: Christian Borntraeger <borntrae...@de.ibm.com>
>
> diff --git a/iothread.c b/iothread.c
> index 1fbf9f1..d9403cf 100644
> --- a/iothread.c
> +++ b/iothread.c
> @@ -30,6 +30,7 @@ typedef ObjectClass IOThreadClass;
> static void *iothread_run(void *opaque)
> {
> IOThread *iothread = opaque;
> + bool blocking;
>
> qemu_mutex_lock(&iothread->init_done_lock);
> iothread->thread_id = qemu_get_thread_id();
> @@ -38,8 +39,10 @@ static void *iothread_run(void *opaque)
>
> while (!iothread->stopping) {
> aio_context_acquire(iothread->ctx);
> - while (!iothread->stopping && aio_poll(iothread->ctx, true)) {
> + blocking = true;
> + while (!iothread->stopping && aio_poll(iothread->ctx, blocking)) {
> /* Progress was made, keep going */
> + blocking = false;
> }
> aio_context_release(iothread->ctx);
> }
>
> Christian, can you test it?
>
> Paolo
>
