Re: [PATCH v9 3/3] scsi: ufs: core: Limit early link recovery in the error handler to runtime PM

[Peter Wang <peter.wang@mediatek.com>]

On Tue, 2026-11-10 at 11:03 +0900, HOYOUNG SEO wrote:
> ufshcd_err_handler() recovers the link without taking hba->host_sem
> whenever hba->pm_op_in_progress is set. That early path was added by
> commit f966e02ae521 ("scsi: ufs: core: Fix runtime suspend error
> deadlock") because the regular error handling would wait for a
> runtime
> PM operation that cannot complete while the error handler is waiting.
> 
> pm_op_in_progress is also set during system suspend, system resume,
> shutdown and poweroff, where the early path is not needed and runs
> concurrently with the PM path itself. For example, if a LINERESET is
> reported and the hibern8 exit fails in __ufshcd_wl_resume() during
> system resume, both ufshcd_err_handler() and __ufshcd_wl_resume()
> call
> ufshcd_link_recovery(), and the host and the device may be reset at
> the
> same time.
> 
> Only take the early path while pm_op_in_progress is set and a runtime
> suspend or resume of the WLUN is in progress. The runtime PM core
> sets
> the runtime status of the WLUN to RPM_SUSPENDING or RPM_RESUMING
> while
> ufshcd_wl_runtime_suspend() or ufshcd_wl_runtime_resume() runs, and
> it
> is RPM_ACTIVE or RPM_SUSPENDED during system PM. The runtime status
> alone is not enough: it also covers the block layer steps before and
> after the driver callbacks, where the early link recovery must not
> run.
> pm_op_in_progress is only set while __ufshcd_wl_suspend() or
> __ufshcd_wl_resume() run, which is inside that window.
> 
> Both checks are done in the new helper
> ufshcd_rpm_transition_in_progress(), next to the other ufshcd_rpm_*()
> helpers. The runtime status is read with READ_ONCE() and without
> power.lock held. It is only available with CONFIG_PM, so the helper
> returns false without it. Both values are read without locking. As
> the
> window of pm_op_in_progress is contained in the runtime PM window, a
> stale value of either one can only make the error handler take the
> regular path, like an error handler that starts just before or after
> the PM operation.
> 
> For the other PM operations the regular error handling is safe:
> 
>   - the system PM callbacks hold host_sem from ufshcd_wl_suspend()
> until
>     ufshcd_wl_resume() returns, and ufshcd_wl_poweroff() holds it as
>     well, so the error handler waits for them;
>   - during shutdown, hba->shutting_down makes the error handler stop.
> 
> This changes the behavior during shutdown: errors that occur while
> the
> final START STOP UNIT command is being processed are no longer
> handled
> by the error handler. Recovery then only happens through
> ufshcd_eh_timed_out().
> 
> Fixes: e23ef4f22db3 ("scsi: ufs: core: Fix error handler host_sem
> issue")
> Signed-off-by: HOYOUNG SEO <hy50.seo@samsung.com>
> ---

Reviewed-by: Peter Wang <peter.wang@mediatek.com>