Re: [Qemu-devel] [PATCH 09/11] migration: add missed aio_context_acquire for state writing/reading

[Stefan Hajnoczi]

On Wed, Nov 04, 2015 at 08:19:40PM +0300, Denis V. Lunev wrote:
> aio_context should be locked in the similar way as was done in QMP
> snapshot creation in the other case there are a lot of possible
> troubles if native AIO mode is enabled for disk.
> 
> qemu_fopen_bdrv and bdrv_fclose are used in real snapshot operations only
> along with block drivers. This change should influence only HMP snapshot
> operations.
> 
> AioContext lock is reqursive. Thus nested locking should not be a problem.

hmp_savevm() and load_vmstate() look up the BlockDriverState and perform
other operations on it.  So the natural place to call acquire/release is
in hmp_savevm() and load_vmstate().  They need that anyway since they
also perform other operations.

qemu_fopen_bdrv() and bdrv_fclose() don't need to worry about
AioContext.

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