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SubjectRe: [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@micron.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@linaro.org>
> Reported-by: Amit Pundir <amit.pundir@linaro.org>
> Tested-by: John Stultz <john.stultz@linaro.org>
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> Signed-off-by: Bean Huo <beanhuo@micron.com>

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

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