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Date: Tue, 16 Jun 2015 17:07:36 +0100
From: Stefan Hajnoczi <stefanha@gmail.com>
Message-ID: <20150616160736.GD4958@stefanha-thinkpad.redhat.com>
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Subject: Re: [Qemu-devel] [Qemu-block] [PATCH v2 02/13] block: Introduce
 bdrv_lock and bdrv_unlock API
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To: Fam Zheng <famz@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>, qemu-block@nongnu.org, qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>


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On Tue, Jun 02, 2015 at 11:21:51AM +0800, Fam Zheng wrote:
> +/**
> + * bdrv_lock:
> + *
> + * Begin a temporary exclusive accessing by locking the BDS.
> + */
> +void bdrv_lock(BlockDriverState *bs);
> +
> +/**
> + * bdrv_unlock:
> + *
> + * End a exclusive accessing.
> + */
> +void bdrv_unlock(BlockDriverState *bs);

This documentation is missing important points:

1. Does AioContext need to be held by the caller?  (Yes)

2. Is this about thread safety?  (No, it's about exclusive access to a
   BDS *within* the AioContext.)

Maybe bdrv_begin_exclusive() and bdrv_end_exclusive() are clearer names?

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