Re: [PATCH 1/2] PM: runtime: Fix I/O hang due to race between resume and runtime disable

[Bart Van Assche]

On 11/26/25 12:17 PM, Rafael J. Wysocki wrote:
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -309,6 +309,8 @@ int blk_queue_enter(struct request_queue
>   		if (flags & BLK_MQ_REQ_NOWAIT)
>   			return -EAGAIN;
>   
> +		/* if necessary, resume .dev (assume success). */
> +		blk_pm_resume_queue(pm, q);
>   		/*
>   		 * read pair of barrier in blk_freeze_queue_start(), we need to
>   		 * order reading __PERCPU_REF_DEAD flag of .q_usage_counter and

blk_queue_enter() may be called from the suspend path so I don't think
that the above change will work. As an example, the UFS driver submits a
SCSI START STOP UNIT command from its runtime suspend callback. The call
chain is as follows:

  ufshcd_wl_runtime_suspend()
    __ufshcd_wl_suspend()
      ufshcd_set_dev_pwr_mode()
        ufshcd_execute_start_stop()
          scsi_execute_cmd()
            scsi_alloc_request()
              blk_queue_enter()
            blk_execute_rq()
            blk_mq_free_request()
              blk_queue_exit()

Thanks,

Bart.