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From: Bart Van Assche <bvanassche@acm.org>
To: Can Guo <cang@codeaurora.org>
Cc: "Martin K . Petersen" <martin.petersen@oracle.com>,
	"James E . J . Bottomley" <jejb@linux.vnet.ibm.com>,
	linux-scsi@vger.kernel.org, Bean Huo <beanhuo@micron.com>,
	Avri Altman <avri.altman@wdc.com>,
	Stanley Chu <stanley.chu@mediatek.com>,
	Tomas Winkler <tomas.winkler@intel.com>
Subject: Re: [PATCH 6/6] ufs: Remove the SCSI timeout handler
Date: Thu, 28 May 2020 20:56:24 -0700	[thread overview]
Message-ID: <efed2865-030a-c98f-5b8f-e9cb008022a4@acm.org> (raw)
In-Reply-To: <8bd12e9fe32b0f996209ac2d4e8aa484@codeaurora.org>

On 2020-05-28 18:39, Can Guo wrote:
> On 2020-05-29 00:12, Bart Van Assche wrote:
>> ufshcd_queuecommand() must have
>> finished before the block layer timeout handler is activated.
>
> This is the ideal/expected situation, but we are seeing the corner case.
> 
> Fixing the root cause of that is one thing, but having the timeout handler
> back can prevent UFS driver from messing up the subsequent requests further
> in such case, causing possible data corruption. Is there any drawbacks if
> we have it back?

Hi Can,

My conclusion from your emails is that ufshcd_queuecommand() can spend
more time than the SCSI timeout (30 seconds) in dma_map_sg(). A
dma_map_sg() call that keeps the CPU busy during more than 30 seconds is
not only weird but it is also a disaster from the point of view of
energy consumption. Please fix the root cause.

Thanks,

Bart.

  reply	other threads:[~2020-05-29  3:56 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-24 22:02 [PATCH 0/6] Six UFS patches Bart Van Assche
2019-12-24 22:02 ` [PATCH 1/6] ufs: Fix indentation in ufshcd_query_attr_retry() Bart Van Assche
2019-12-25  7:16   ` Stanley Chu
2019-12-25  8:17   ` Can Guo
2019-12-27  1:13   ` Alim Akhtar
2019-12-24 22:02 ` [PATCH 2/6] ufs: Make ufshcd_add_command_trace() easier to read Bart Van Assche
2019-12-25  7:16   ` Stanley Chu
2019-12-25  8:17   ` Can Guo
2019-12-27  1:17   ` Alim Akhtar
2019-12-24 22:02 ` [PATCH 3/6] ufs: Make ufshcd_prepare_utp_scsi_cmd_upiu() " Bart Van Assche
2019-12-25  7:17   ` Stanley Chu
2019-12-25  8:18   ` Can Guo
2019-12-24 22:02 ` [PATCH 4/6] ufs: Fix a race condition in the tracing code Bart Van Assche
2019-12-25 10:59   ` Can Guo
2019-12-26 17:35     ` Bart Van Assche
2019-12-27  5:50       ` Can Guo
2019-12-27  1:21   ` Alim Akhtar
2019-12-24 22:02 ` [PATCH 5/6] ufs: Remove superfluous memory barriers Bart Van Assche
2019-12-25 10:31   ` Can Guo
2019-12-26 17:36     ` Bart Van Assche
2019-12-24 22:02 ` [PATCH 6/6] ufs: Remove the SCSI timeout handler Bart Van Assche
2019-12-25 11:02   ` Can Guo
2019-12-27  1:24   ` Alim Akhtar
2020-05-28  9:47   ` Can Guo
2020-05-28 16:12     ` Bart Van Assche
2020-05-29  1:39       ` Can Guo
2020-05-29  3:56         ` Bart Van Assche [this message]
2020-01-03  2:58 ` [PATCH 0/6] Six UFS patches Martin K. Petersen

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