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Subject: Re: [PATCH v3 8/9] scsi: ufs: Update the fast abort path in
 ufshcd_abort() for PM requests
To:     Can Guo <cang@codeaurora.org>
Cc:     asutoshd@codeaurora.org, nguyenb@codeaurora.org,
        hongwus@codeaurora.org, ziqichen@codeaurora.org,
        linux-scsi@vger.kernel.org, kernel-team@android.com,
        Alim Akhtar <alim.akhtar@samsung.com>,
        Avri Altman <avri.altman@wdc.com>,
        "James E.J. Bottomley" <jejb@linux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        Stanley Chu <stanley.chu@mediatek.com>,
        Bean Huo <beanhuo@micron.com>,
        Jaegeuk Kim <jaegeuk@kernel.org>,
        open list <linux-kernel@vger.kernel.org>
References: <1623300218-9454-1-git-send-email-cang@codeaurora.org>
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 <fa37645b-3c1e-2272-d492-0c2b563131b1@acm.org>
 <16f5bd448c7ae1a45fcb23133391aa3f@codeaurora.org>
From:   Bart Van Assche <bvanassche@acm.org>
Message-ID: <926d8c4a-0fbf-a973-188a-b10c9acaa444@acm.org>
Date:   Sat, 12 Jun 2021 09:50:51 -0700
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On 6/12/21 12:07 AM, Can Guo wrote:
> Sigh... I also want my life and work to be easier...

How about reducing the number of states and state transitions in the UFS
driver?

One source of complexity is that ufshcd_err_handler() is scheduled
independently of the SCSI error handler and hence may run concurrently
with the SCSI error handler. Has the following already been considered?
- Call ufshcd_err_handler() synchronously from ufshcd_abort() and
ufshcd_eh_host_reset_handler() instead of asynchronously.
- Call scsi_schedule_eh() from ufshcd_uic_pwr_ctrl() and
ufshcd_check_errors() instead of ufshcd_schedule_eh_work().

These changes will guarantee that all commands have completed or timed
out before ufshcd_err_handler() is called. I think that would allow to
remove e.g. the following code from the error handler:

	ufshcd_scsi_block_requests(hba);
	/* Drain ufshcd_queuecommand() */
	down_write(&hba->clk_scaling_lock);
	up_write(&hba->clk_scaling_lock);

Thanks,

Bart.