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Date: Fri, 14 Jun 2013 10:12:00 -0400
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Subject: Re: [Qemu-devel] [RFC 08/13] block: drop bdrv_get_aio_context()
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To: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Anthony Liguori <aliguori@us.ibm.com>, Ping Fan Liu <pingfank@linux.vnet.ibm.com>, qemu-devel@nongnu.org

Il 14/06/2013 05:48, Stefan Hajnoczi ha scritto:
> Associating a BlockDriverState with a single AioContext is not flexible
> enough.  Once we make BlockDriverState thread-safe, it will be possible
> to call bdrv_*() functions from multiple event loops.

I'm afraid that this is trading some pain now (converting
qemu_bh_new/qemu_set_fd_handler to aio_bh_new/aio_set_fd_handler) for
more pain later (having to make BDS thread-safe).  There aren't that
many (~40) in block layer code.

Making BlockDriverState thread-safe is hard, it is much simpler to run
all the BlockDriverState code in the AioContext thread itself.

There are some things that cannot (basically monitor commands and other
places that are currently using bdrv_drain_all) but they can simply take
a "big AioContext lock".

Paolo