On 2020-01-26 11:29, Bart Van Assche wrote:
On 2020-01-22 23:25, Can Guo wrote:
diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 1201578..c2de29f 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -4760,8 +4760,15 @@ static void ufshcd_slave_destroy(struct
scsi_device *sdev)
* UFS device needs urgent BKOPs.
*/
if (!hba->pm_op_in_progress &&
- ufshcd_is_exception_event(lrbp->ucd_rsp_ptr))
- schedule_work(&hba->eeh_work);
+ ufshcd_is_exception_event(lrbp->ucd_rsp_ptr)) {
+ /*
+ * Prevent suspend once eeh_work is scheduled
+ * to avoid deadlock between ufshcd_suspend
+ * and exception event handler.
+ */
+ if (schedule_work(&hba->eeh_work))
+ pm_runtime_get_noresume(hba->dev);
+ }
Please combine the two logical tests with "&&" instead of nesting two
if-statements inside each other.
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?
Thanks,
Bart.
Hi Bart,
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.
Thanks,
Can Guo.
