Re: [PATCH 2/2] scsi: ufs: Fix a deadlock in the error handler

From: Bart Van Assche <bvanassche@acm.org>
To: Christoph Hellwig <hch@infradead.org>,
	Adrian Hunter <adrian.hunter@intel.com>
Cc: "Martin K . Petersen" <martin.petersen@oracle.com>,
	Jaegeuk Kim <jaegeuk@kernel.org>,
	linux-scsi@vger.kernel.org,
	"James E.J. Bottomley" <jejb@linux.ibm.com>,
	Can Guo <cang@codeaurora.org>, Bean Huo <beanhuo@micron.com>,
	Stanley Chu <stanley.chu@mediatek.com>,
	Asutosh Das <asutoshd@codeaurora.org>,
	Hannes Reinecke <hare@suse.com>,
	John Garry <john.garry@huawei.com>
Subject: Re: [PATCH 2/2] scsi: ufs: Fix a deadlock in the error handler
Date: Wed, 3 Nov 2021 09:48:20 -0700	[thread overview]
Message-ID: <ac927e92-f69f-a21a-5b3f-7672853fd2d6@acm.org> (raw)
In-Reply-To: <YYK59D+M5w4FSoo0@infradead.org>

On 11/3/21 9:33 AM, Christoph Hellwig wrote:
> On Wed, Nov 03, 2021 at 10:37:30AM +0200, Adrian Hunter wrote:
>> The UFS driver does not issue device commands to the block layer.
>> blk_get_request() is used only to get a free slot.
> 
> That is indeed the case for the code touched here, but not in general:
> 
> ch@brick:~/work/linux$ git-grep blk_execute_rq drivers/scsi/ufs/
> drivers/scsi/ufs/ufshcd.c:      blk_execute_rq_nowait(/*bd_disk=*/NULL, req, /*at_head=*/true,
> drivers/scsi/ufs/ufshpb.c:      blk_execute_rq_nowait(NULL, req, 1, ufshpb_umap_req_compl_fn);
> drivers/scsi/ufs/ufshpb.c:      blk_execute_rq_nowait(NULL, req, 1, ufshpb_map_req_compl_fn);

Hi Christoph,

The blk_execute_rq_nowait() call in drivers/scsi/ufs/ufshcd.c will disappear
from Linus' master branch once Linus merges the v5.16 scsi core pull request.
See also the following patch authored by myself: "[PATCH 2/2] scsi: ufs: Stop
clearing unit attentions"
(https://lore.kernel.org/linux-scsi/20211001182015.1347587-3-jaegeuk@kernel.org/).

Thanks,

Bart.