linux-kernel - Re: [REGRESSION] CPUIDLE_FLAG_RCU_IDLE, blk_mq_freeze_queue

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Date:   Fri, 17 Mar 2023 01:38:27 +0000
From:   Alexey Klimov <alexey.klimov@...aro.org>
To:     Bart Van Assche <bvanassche@....org>
Cc:     peterz@...radead.org, draszik@...gle.com, peter.griffin@...aro.org,
        willmcvicker@...gle.com, mingo@...nel.org, ulf.hansson@...aro.org,
        tony@...mide.com, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, axboe@...nel.dk,
        alim.akhtar@...sung.com, regressions@...ts.linux.dev,
        avri.altman@....com, klimova@...gle.com
Subject: Re: [REGRESSION] CPUIDLE_FLAG_RCU_IDLE, blk_mq_freeze_queue_wait()
 and slow-stuck reboots

On Tue, 14 Mar 2023 at 23:21, Bart Van Assche <bvanassche@....org> wrote:
>
> On 3/14/23 16:00, Alexey Klimov wrote:
> > The delay is found to be in device's ->shutdown() methods called from kernel_restart():
> > void kernel_restart_prepare(char *cmd)
> > {
> >       blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd);
> >       system_state = SYSTEM_RESTART;
> >       usermodehelper_disable();
> >       device_shutdown();      <---- here

[..]

>
> Please let me know if you want me to resubmit patch "scsi: ufs: Remove
> the LUN quiescing code from ufshcd_wl_shutdown()"
> (https://lore.kernel.org/linux-scsi/20220331223424.1054715-14-bvanassche@acm.org/).

This indeed works and helps to reduce reboot time. Thanks!
If you decide to resubmit, feel free to ping me to test it.
However I have no knowledge how comments from Adrian can be addressed.

With that patch the reboot time decreases from 60-100 seconds to
~10-20 seconds. The next
"slow" thing is wlan driver which callback is called from
blocking_notifier_call_chain(&reboot_notifier_list, ...) but obviously
it is not a part of ufs code.

Best regards,
Alexey