Commit 52de3d30 authored Dec 08, 2017 by Sayali Lokhande

scsi: ufs: Avoid deadlock in suspend and eeh_work



In case of an exception, there could be a deadlock:

eeh_work:
-002|schedule()
-003|spin_lock_irq()
-003|rpm_resume << pm_runtime_get_sync(hba->dev);
-004|__pm_runtime_resume()
-005|ufshcd_scsi_block_requests()
-005|ufshcd_exception_event_handler()

ufshcd_suspend:
-002|schedule()
-003|schedule_timeout()
-004|do_wait_for_common()
-004|__wait_for_common()
-004|wait_for_common()
-005|wait_for_completion()
-006|destroy_work_on_stack()
-006|flush_work(?) << eeh_work
-007|ufshcd_suspend()
-008|ufshcd_runtime_suspend()
-009|ufshcd_pltfrm_runtime_suspend()
-010|pm_generic_runtime_suspend()
-011|__rpm_callback()

Scenario looks like :
1.Hba->eeh_work starts to work and at the almost same
time ufshcd_runtime_suspend start to work by rpm core.
2.pm_runtime_get_sync in eeh_work remains pending as
rpm_status is RPM_SUSPENDING due to ufshcd_runtime_suspend.

To fix this, call pm_runtime_get_noresume() once eeh_work
is scheduled so that suspend cannot be invoked during
exception work.

Change-Id: Ib212f71e22f063dad9c6ccca4aa8f7261e568b51
Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
Signed-off-by: Sayali Lokhande <sayalil@codeaurora.org>

parent 21a1b0f4

drivers/scsi/ufs/ufshcd.c

+16 −2

Original line number	Diff line number	Diff line
		@@ -5561,8 +5561,15 @@ ufshcd_transfer_rsp_status(struct ufs_hba hba, struct ufshcd_lrb lrbp)
		* 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);
		}
		break;
		case UPIU_TRANSACTION_REJECT_UPIU:
		/* TODO: handle Reject UPIU Response */
		@@ -6146,6 +6153,13 @@ static void ufshcd_exception_event_handler(struct work_struct *work)

		out:
		ufshcd_scsi_unblock_requests(hba);
		/*
		* 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;
		}