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From: Bart Van Assche <bvanassche@acm.org>
To: jejb@linux.ibm.com, daejun7.park@samsung.com,
	ALIM AKHTAR <alim.akhtar@samsung.com>,
	"avri.altman@wdc.com" <avri.altman@wdc.com>,
	"martin.petersen@oracle.com" <martin.petersen@oracle.com>,
	"huobean@gmail.com" <huobean@gmail.com>,
	Keoseong Park <keosung.park@samsung.com>
Cc: "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH] scsi: ufs: Fix proper API to send HPB pre-request
Date: Thu, 28 Oct 2021 08:59:25 -0700	[thread overview]
Message-ID: <0d66b6d0-26c6-573f-e2a0-022e22c47b52@acm.org> (raw)
In-Reply-To: <0f9229c3c4c7859524411a47db96a3b53ac89c90.camel@linux.ibm.com>

On 10/28/21 7:28 AM, James Bottomley wrote:
> If the block people are happy with this, then I'm OK with it, but it
> doesn't look like you've solved the fanout deadlock problem because
> this new mechanism is still going to allocate a new tag.

(+Jens, Christoph and linux-block)

Hi James,

My understanding is that the UFS HPB code makes ufshcd_queuecommand()
return SCSI_MLQUEUE_HOST_BUSY if the pool with pre-allocated requests is
exhausted. This will make the SCSI core reissue a SCSI command until
completion of another command has freed up one of the pre-allocated
requests. This is not the most efficient approach but should not trigger
a deadlock.

Thanks,

Bart.

  parent reply	other threads:[~2021-10-28 15:59 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CGME20211027223619epcms2p60bbc74c9ba9757c58709a99acd0892ff@epcms2p6>
2021-10-27 22:36 ` [PATCH] scsi: ufs: Fix proper API to send HPB pre-request Daejun Park
2021-10-28  4:16   ` Bart Van Assche
2021-10-28 14:28   ` James Bottomley
2021-10-28 15:27     ` Christoph Hellwig
2021-10-28 17:07       ` Bart Van Assche
2021-10-28 17:10         ` Christoph Hellwig
2021-10-28 15:59     ` Bart Van Assche [this message]
2021-10-28 19:12       ` James Bottomley
2021-10-28 20:04         ` Bart Van Assche
2021-10-28 20:12           ` James Bottomley
2021-10-28 21:20         ` Daejun Park
2021-10-28 15:22   ` James Bottomley
2021-10-29  1:32   ` Ming Lei
2021-10-29  1:50     ` Daejun Park
2021-10-29  2:10       ` Ming Lei
2021-10-29  2:50         ` Daejun Park
2021-10-29  3:14           ` Ming Lei
2021-10-29  4:39             ` Daejun Park

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