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Date: Fri, 14 Oct 2016 22:50:25 +0800
From: Fam Zheng <famz@redhat.com>
Message-ID: <20161014145025.GA17349@lemon>
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Subject: Re: [Qemu-devel] [PATCH 12/18] iothread: detach all block devices
 before stopping them
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org, kwolf@redhat.com, stefanha@redhat.com

On Thu, 10/13 19:34, Paolo Bonzini wrote:
> Soon bdrv_drain will not call aio_poll itself on iothreads.  If block
> devices are left hanging off the iothread's AioContext, there will be no
> one to do I/O for those poor devices.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  iothread.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/iothread.c b/iothread.c
> index 62c8796..8153e21 100644
> --- a/iothread.c
> +++ b/iothread.c
> @@ -16,6 +16,7 @@
>  #include "qom/object_interfaces.h"
>  #include "qemu/module.h"
>  #include "block/aio.h"
> +#include "block/block.h"
>  #include "sysemu/iothread.h"
>  #include "qmp-commands.h"
>  #include "qemu/error-report.h"
> @@ -199,6 +200,15 @@ IOThreadInfoList *qmp_query_iothreads(Error **errp)
>  void iothread_stop_all(void)
>  {
>      Object *container = object_get_objects_root();
> +    BlockDriverState *bs;
> +    BdrvNextIterator it;
> +
> +    for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
> +        AioContext *ctx = bdrv_get_aio_context(bs);

I have a strong feeling that we should 'continue' if ctx ==
qemu_get_aio_context() - otherwise a lot of unnecessary (and somehow
complicated) code will always run, even if user has no iothread.

Fam

> +        aio_context_acquire(ctx);
> +        bdrv_set_aio_context(bs, qemu_get_aio_context());
> +        aio_context_release(ctx);
> +    }
>  
>      object_child_foreach(container, iothread_stop, NULL);
>  }
> -- 
> 2.7.4
> 
>