Error recovery can be invoked from multiple code paths, including hibern8
enter/exit (from ufshcd_link_recovery), ufshcd_eh_host_reset_handler() and
eh_work scheduled from IRQ context. Ultimately, these paths are all trying
to invoke ufshcd_reset_and_restore() in either a synchronous or
asynchronous manner. This causes problems:
- If link recovery happens during ungate work, ufshcd_hold() would be
called recursively. Although commit 53c12d0ef6 ("scsi: ufs: fix error
recovery after the hibern8 exit failure") fixed a deadlock due to
recursive calls of ufshcd_hold() by adding a check of eh_in_progress
into ufshcd_hold, this check allows eh_work to run in parallel while
link recovery is running.
- Similar concurrency can also happen when error recovery is invoked from
ufshcd_eh_host_reset_handler and ufshcd_link_recovery.
- Concurrency can even happen between eh_works. eh_work, currently queued
on system_wq, is allowed to have multiple instances running in parallel,
but we don't have proper protection for that.
If any of above concurrency scenarios happen, error recovery would fail and
lead ufs device and host into bad states. To fix the concurrency problem,
this change queues eh_work on a single threaded workqueue and removes link
recovery calls from the hibern8 enter/exit path. In addition, make use of
eh_work in eh_host_reset_handler instead of calling
ufshcd_reset_and_restore. This unifies the UFS error recovery mechanism.
According to the UFSHCI JEDEC spec, hibern8 enter/exit error occurs when
the link is broken. This essentially applies to any power mode change
operations (since they all use PACP_PWR cmds in UniPro layer). So, if a
power mode change operation (including AH8 enter/exit) fails, mark link
state as UIC_LINK_BROKEN_STATE and schedule the eh_work. In this case,
error handler needs to do a full reset and restore to recover the link back
to active. Before the link state is recovered to active,
ufshcd_uic_pwr_ctrl simply returns -ENOLINK to avoid more errors.
Link: https://lore.kernel.org/r/1596975355-39813-6-git-send-email-cang@codeaurora.org
Reviewed-by: Bean Huo <beanhuo@micron.com>
Reviewed-by: Asutosh Das <asutoshd@codeaurora.org>
Signed-off-by: Can Guo <cang@codeaurora.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
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