[PATCH v1] ufs: core: bypass get rpm when err handling with pm_op_in_progress

[Bart Van Assche]

On 9/19/22 07:47, Peter Wang wrote:
> If the scsi error happened and need do ufshcd_eh_host_reset_handler, the 
> rpm state should in RPM_ACTIVE.
> Because scsi need wakeup suspended LUN, and send command to LUN then get 
> error, right?

The following sequence may activate the SCSI error handler while the RPM 
state is RPM_RESUMING:
* The RPM state is RPM_SUSPENDED.
* The RPM state is changed into RPM_RESUMING and ufshcd_wl_resume() is 
called.
* ufshcd_set_dev_pwr_mode() calls scsi_execute() and the START STOP UNIT 
command times out.
* Because of this timeout the SCSI error handler is activated.

> If remove ufshcd_rpm_get_sync directly, think about this case.
> ufshcd_err_handler is on going and try to abort some task (which may get 
> stuck and timeout too).
> Then rpm count down try to suspend. Finally runtime suspend callback may 
> return IO error and IO hang.

Hmm ... suspending a UFS device involves calling ufshcd_wl_shutdown(), 
ufshcd_set_dev_pwr_mode() and scsi_execute(). scsi_execute() is 
serialized against the UFS error handler because the latter calls 
ufshcd_scsi_block_requests().

Thanks,

Bart.