Re: [PATCH v2 0/4] scsi: eliminate AioContext lock

[Kevin Wolf]

[ Cc: qemu-block ]

Am 04.12.2023 um 17:42 hat Stefan Hajnoczi geschrieben:
> v2:
> - Reschedule BH in new AioContext if change is detected [Kevin]
> - Drop stray "remember" in Patch 2's commit description [Eric]
> 
> The SCSI subsystem uses the AioContext lock to protect internal state. This is
> necessary because the main loop and the IOThread can access SCSI state in
> parallel. This inter-thread access happens during scsi_device_purge_requests()
> and scsi_dma_restart_cb().
> 
> This patch series modifies the code so SCSI state is only accessed from the
> IOThread that is executing requests. Once this has been achieved the 
> AioContext
> lock is no longer necessary.
> 
> Note that a few aio_context_acquire()/aio_context_release() calls still remain
> after this series. They surround API calls that invoke AIO_WAIT_WHILE() and
> therefore still rely on the AioContext lock for now.
> 
> Stefan Hajnoczi (4):
>   scsi: only access SCSIDevice->requests from one thread
>   virtio-scsi: don't lock AioContext around
>     virtio_queue_aio_attach_host_notifier()
>   scsi: don't lock AioContext in I/O code path
>   dma-helpers: don't lock AioContext in dma_blk_cb()

Thanks, applied to the block branch.

Kevin