Re: [PATCH] ufs: core: Fix a deadlock in the frequency scaling code

["Alexey Klimov" <alexey.klimov@linaro.org>]

On Thu Dec 4, 2025 at 6:15 PM GMT, Bart Van Assche wrote:
> Commit 08b12cda6c44 ("scsi: ufs: core: Switch to scsi_get_internal_cmd()")
> accidentally introduced a deadlock in the frequency scaling code.
> ufshcd_clock_scaling_unprepare() may submit a device management command
> while SCSI command processing is blocked. The deadlock was introduced by
> using the SCSI core for submitting device management commands
> (scsi_get_internal_cmd() + blk_execute_rq()). Fix this deadlock by calling
> blk_mq_unquiesce_tagset() before any device management commands are
> submitted by ufshcd_clock_scaling_unprepare().
>
> Fixes: 08b12cda6c44 ("scsi: ufs: core: Switch to scsi_get_internal_cmd()")
> Reported-by: Manivannan Sadhasivam <mani@kernel.org>
> Reported-by: Roger Shimizu <rosh@debian.org>
> Closes: https://lore.kernel.org/linux-scsi/ehorjaflathzab5oekx2nae2zss5vi2r36yqkqsfjb2fgsifz2@yk3us5g3igow/
> Tested-by: Roger Shimizu <rosh@debian.org>
> Cc: Nitin Rawat <nitin.rawat@oss.qualcomm.com>
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>

This fixes the regression of freezing/hanging boot in initramfs
on Qcom RB5 board with recent linux-nexts. Thank you!

Tested-by: Alexey Klimov <alexey.klimov@linaro.org> # RB5 board

Best regards,
Alexey