On 2020-02-04 11:12, Bart Van Assche wrote:
On 2020-02-02 22:23, Can Guo wrote:
On 2020-01-26 11:29, Bart Van Assche wrote:
On 2020-01-22 23:25, Can Guo wrote:
break;
case UPIU_TRANSACTION_REJECT_UPIU:
/* TODO: handle Reject UPIU Response */
@@ -5215,7 +5222,14 @@ static void
ufshcd_exception_event_handler(struct work_struct *work)
out:
scsi_unblock_requests(hba->host);
- pm_runtime_put_sync(hba->dev);
+ /*
+ * pm_runtime_get_noresume is called while scheduling
+ * eeh_work to avoid suspend racing with exception work.
+ * Hence decrement usage counter using pm_runtime_put_noidle
+ * to allow suspend on completion of exception event handler.
+ */
+ pm_runtime_put_noidle(hba->dev);
+ pm_runtime_put(hba->dev);
return;
}
@@ -7901,6 +7915,7 @@ static int ufshcd_suspend(struct ufs_hba *hba,
enum ufs_pm_op pm_op)
goto enable_gating;
}
+ flush_work(&hba->eeh_work);
ret = ufshcd_link_state_transition(hba, req_link_state, 1);
if (ret)
goto set_dev_active;
I think this patch introduces a new race condition, namely the
following:
- ufshcd_slave_destroy() tests pm_op_in_progress and reads the value
zero from that variable.
- ufshcd_suspend() sets hba->pm_op_in_progress to one.
- ufshcd_slave_destroy() calls schedule_work().
How about fixing this race condition by calling
pm_runtime_get_noresume() before checking pm_op_in_progress and by
reallowing resume if no work is scheduled?
If you apply this patch, you will find the change is not in
ufshcd_slave_destroy(), but in ufshcd_transfer_rsp_status().
So the racing you mentioned above does not exist.
Hi Can,
Apparently I got a function name wrong. Can the following race
condition
happen:
- ufshcd_transfer_rsp_status() tests pm_op_in_progress and reads the
value zero from that variable.
- ufshcd_suspend() sets hba->pm_op_in_progress to one.
- ufshcd_suspend() calls flush_work(&hba->eeh_work).
- ufshcd_transfer_rsp_status() calls schedule_work(&hba->eeh_work).
Thanks,
Bart.
Hi Bart,
The sequence you mentioned is not possible.
In normal cases, before ufshcd_transfer_rsp_status() returns,
ufshcd_suspend() would not be called (unless you intentionally call
ufshcd_suspend() to screw it). Because ufshcd_transfer_rsp_status() is
called from __ufshcd_transfer_req_compl(), which is being used by either
UFS IRQ handler or err handler. Meanwhile, in
__ufshcd_transfer_req_compl(),
scsi_done() is called only after ufshcd_transfer_rsp_status() returns.
When
we are here, it means UFS driver is still handling requests/tasks, so
suspend
would not kick start at this moment, either runtime suspend or system
suspend.
And this is why below lines work, calling pm_runtime_get_noresume()
within
ufshcd_transfer_rsp_status() can prevent runtime suspend from happening
after we leave ufshcd_transfer_rsp_status().
+ if (schedule_work(&hba->eeh_work))
+ pm_runtime_get_noresume(hba->dev);
Thanks,
Can Guo.
