From: Kevin Wolf <kwolf@redhat.com>
To: Stefan Hajnoczi <stefanha@redhat.com>
Cc: qemu-devel@nongnu.org, "Michael S. Tsirkin" <mst@redhat.com>,
"David Hildenbrand" <david@redhat.com>,
"Philippe Mathieu-Daudé" <philmd@linaro.org>,
"Peter Xu" <peterx@redhat.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Fam Zheng" <fam@euphon.net>
Subject: Re: [PATCH 4/4] dma-helpers: don't lock AioContext in dma_blk_cb()
Date: Fri, 1 Dec 2023 17:48:36 +0100 [thread overview]
Message-ID: <ZWoOZEZdxbJy5W9x@redhat.com> (raw)
In-Reply-To: <20231123194931.171598-5-stefanha@redhat.com>
Am 23.11.2023 um 20:49 hat Stefan Hajnoczi geschrieben:
> Commit abfcd2760b3e ("dma-helpers: prevent dma_blk_cb() vs
> dma_aio_cancel() race") acquired the AioContext lock inside dma_blk_cb()
> to avoid a race with scsi_device_purge_requests() running in the main
> loop thread.
>
> The SCSI code no longer calls dma_aio_cancel() from the main loop thread
> while I/O is running in the IOThread AioContext. Therefore it is no
> longer necessary to take this lock to protect DMAAIOCB fields. The
> ->cb() function also does not require the lock because blk_aio_*() and
> friends do not need the AioContext lock.
>
> Both hw/ide/core.c and hw/ide/macio.c also call dma_blk_io() but don't
> rely on it taking the AioContext lock, so this change is safe.
>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
The commit message neglects to talk about dbs->io_func, which is what
took the AioContext lock even before commit abfcd2760b3e. I think the
reason is the same as for the previous patch.
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
next prev parent reply other threads:[~2023-12-01 16:49 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-23 19:49 [PATCH 0/4] scsi: eliminate AioContext lock Stefan Hajnoczi
2023-11-23 19:49 ` [PATCH 1/4] scsi: only access SCSIDevice->requests from one thread Stefan Hajnoczi
2023-11-27 15:14 ` Eric Blake
2023-12-01 16:03 ` Kevin Wolf
2023-12-04 16:30 ` Stefan Hajnoczi
2023-12-05 10:00 ` Kevin Wolf
2023-12-06 16:25 ` Stefan Hajnoczi
2023-11-23 19:49 ` [PATCH 2/4] virtio-scsi: don't lock AioContext around virtio_queue_aio_attach_host_notifier() Stefan Hajnoczi
2023-11-27 15:21 ` Eric Blake
2023-12-04 15:37 ` Stefan Hajnoczi
2023-12-01 16:11 ` Kevin Wolf
2023-11-23 19:49 ` [PATCH 3/4] scsi: don't lock AioContext in I/O code path Stefan Hajnoczi
2023-11-27 15:58 ` Eric Blake
2023-12-01 16:38 ` Kevin Wolf
2023-11-23 19:49 ` [PATCH 4/4] dma-helpers: don't lock AioContext in dma_blk_cb() Stefan Hajnoczi
2023-11-27 18:46 ` Eric Blake
2023-12-01 16:48 ` Kevin Wolf [this message]
2023-11-23 19:57 ` [PATCH 0/4] scsi: eliminate AioContext lock Stefan Hajnoczi
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