linux-kernel - Re: [PATCH v2] scsi: ufs: Fix deadlock issue in ufshcd_wait_for_doorbell

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Date:   Wed, 15 Dec 2021 10:49:02 -0800
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Bean Huo <huobean@...il.com>
Cc:     alim.akhtar@...sung.com, avri.altman@....com,
        asutoshd@...eaurora.org, jejb@...ux.ibm.com,
        martin.petersen@...cle.com, stanley.chu@...iatek.com,
        beanhuo@...ron.com, bvanassche@....org, tomas.winkler@...el.com,
        cang@...eaurora.org, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org, YongQin Liu <yongqin.liu@...aro.org>,
        Amit Pundir <amit.pundir@...aro.org>,
        John Stultz <john.stultz@...aro.org>
Subject: Re: [PATCH v2] scsi: ufs: Fix deadlock issue in
 ufshcd_wait_for_doorbell_clr()

On Tue 14 Dec 04:05 PST 2021, Bean Huo wrote:

> From: Bean Huo <beanhuo@...ron.com>
> 
> Call shost_for_each_device() with holding host->host_lock will cause
> a deadlock situation, which will cause the system to stall (the log
> as follow). Fix this issue by using __shost_for_each_device() in
> ufshcd_pending_cmds().
> 
> stalls on CPUs/tasks:
> all trace:
> __switch_to+0x120/0x170
> 0xffff800011643998
> ask dump for CPU 5:
> ask:kworker/u16:2   state:R  running task     stack:    0 pid:   80 ppid:     2 flags:0x0000000a
> orkqueue: events_unbound async_run_entry_fn
> all trace:
> __switch_to+0x120/0x170
> 0x0
> ask dump for CPU 6:
> ask:kworker/u16:6   state:R  running task     stack:    0 pid:  164 ppid:     2 flags:0x0000000a
> orkqueue: events_unbound async_run_entry_fn
> all trace:
> __switch_to+0x120/0x170
> 0xffff54e7c4429f80
> ask dump for CPU 7:
> ask:kworker/u16:4   state:R  running task     stack:    0 pid:  153 ppid:     2 flags:0x0000000a
> orkqueue: events_unbound async_run_entry_fn
> all trace:
> __switch_to+0x120/0x170
> blk_mq_run_hw_queue+0x34/0x110
> blk_mq_sched_insert_request+0xb0/0x120
> blk_execute_rq_nowait+0x68/0x88
> blk_execute_rq+0x4c/0xd8
> __scsi_execute+0xec/0x1d0
> scsi_vpd_inquiry+0x84/0xf0
> scsi_get_vpd_buf+0x34/0xb8
> scsi_attach_vpd+0x34/0x140
> scsi_probe_and_add_lun+0xa6c/0xab8
> __scsi_scan_target+0x438/0x4f8
> scsi_scan_channel+0x6c/0xa8
> scsi_scan_host_selected+0xf0/0x150
> do_scsi_scan_host+0x88/0x90
> scsi_scan_host+0x1b4/0x1d0
> ufshcd_async_scan+0x248/0x310
> async_run_entry_fn+0x30/0x178
> process_one_work+0x1e8/0x368
> worker_thread+0x40/0x478
> kthread+0x174/0x180
> ret_from_fork+0x10/0x20
> 
> Fixes: 8d077ede48c1 ("scsi: ufs: Optimize the command queueing code")
> Reported-by: YongQin Liu <yongqin.liu@...aro.org>
> Reported-by: Amit Pundir <amit.pundir@...aro.org>
> Tested-by: John Stultz <john.stultz@...aro.org>
> Signed-off-by: Bart Van Assche <bvanassche@....org>
> Signed-off-by: Bean Huo <beanhuo@...ron.com>

Reviewed-by: Bjorn Andersson <bjorn.andersson@...aro.org>
Tested-by: Bjorn Andersson <bjorn.andersson@...aro.org>

Regards,
Bjorn

> ---
>  drivers/scsi/ufs/ufshcd.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index 6dd517267f1b..fbebb8309ef7 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -1082,7 +1082,8 @@ static u32 ufshcd_pending_cmds(struct ufs_hba *hba)
>  	struct scsi_device *sdev;
>  	u32 pending = 0;
>  
> -	shost_for_each_device(sdev, hba->host)
> +	lockdep_assert_held(hba->host->host_lock);
> +	__shost_for_each_device(sdev, hba->host)
>  		pending += sbitmap_weight(&sdev->budget_map);
>  
>  	return pending;
> -- 
> 2.25.1
> 
>