Re: [PATCH] scsi: ufs: core: Quiesce SCSI devices instead of host tagset during error handling

[Bart Van Assche <bvanassche@acm.org>]

On 9/2/26 1:23 AM, Stanley Jhu wrote:
> Commit 08b12cda6c44 ("scsi: ufs: core: Switch to scsi_get_internal_cmd()")
> switched UFS internal commands to allocate requests on
> hba->host->pseudo_sdev->request_queue, which shares the host tagset with
> regular LUNs.
> 
> During error recovery, ufshcd_err_handling_prepare() calls
> blk_mq_quiesce_tagset(&hba->host->tag_set), marking all queues in the
> tagset as quiesced, including pseudo_sdev->request_queue. When
> ufshcd_verify_dev_init() subsequently issues internal commands (e.g. NOP
> OUT UPIU) via blk_execute_rq(), blk_mq_run_hw_queue() skips running the
> quiesced queue, resulting in an unrecoverable circular wait deadlock.
> 
> Resolve this by quiescing only logical units attached to the host via
> shost_for_each_device() during error handling. Because
> shost_for_each_device() explicitly skips pseudo SCSI devices (via
> scsi_device_is_pseudo_dev() in __scsi_iterate_devices()), regular LUNs
> are quiesced to prevent retry storms, while pseudo_sdev remains
> unquiesced so internal commands can be dispatched and completed during
> error recovery.
> 
> Clock scaling and command pause (ufshcd_pause_command_processing) paths
> continue to use blk_mq_quiesce_tagset() as they require freezing all
> queues including internal commands.
Reviewed-by: Bart Van Assche <bvanassche@acm.org>