linux-kernel - Re: [PATCH v3 8/9] scsi: ufs: Update the fast abort path in ufshcd

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Message-ID: <926d8c4a-0fbf-a973-188a-b10c9acaa444@acm.org>
Date:   Sat, 12 Jun 2021 09:50:51 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Can Guo <cang@...eaurora.org>
Cc:     asutoshd@...eaurora.org, nguyenb@...eaurora.org,
        hongwus@...eaurora.org, ziqichen@...eaurora.org,
        linux-scsi@...r.kernel.org, kernel-team@...roid.com,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Stanley Chu <stanley.chu@...iatek.com>,
        Bean Huo <beanhuo@...ron.com>,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 8/9] scsi: ufs: Update the fast abort path in
 ufshcd_abort() for PM requests

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.