[PATCH v3 1/1] scsi: ufs: core: fix device management cmd timeout flow

[Mason Zhang]

From: Mason Zhang <Mason.Zhang at mediatek.com>

In ufs error handler flow, host will send device management cmd(NOP OUT)
to device for recovery link. If cmd response timeout, and clear doorbell
fail, ufshcd_wait_for_dev_cmd will do nothing and return,
hba->dev_cmd.complete struct not set to null.

In this time, if cmd has been responsed by device, then it will
call complete() in __ufshcd_transfer_req_compl, because of complete
struct is alloced in stack, then the KE will occur.

Fix the following crash:
  ipanic_die+0x24/0x38 [mrdump]
  die+0x344/0x748
  arm64_notify_die+0x44/0x104
  do_debug_exception+0x104/0x1e0
  el1_dbg+0x38/0x54
  el1_sync_handler+0x40/0x88
  el1_sync+0x8c/0x140
  queued_spin_lock_slowpath+0x2e4/0x3c0
  __ufshcd_transfer_req_compl+0x3b0/0x1164
  ufshcd_trc_handler+0x15c/0x308
  ufshcd_host_reset_and_restore+0x54/0x260
  ufshcd_reset_and_restore+0x28c/0x57c
  ufshcd_err_handler+0xeb8/0x1b6c
  process_one_work+0x288/0x964
  worker_thread+0x4bc/0xc7c
  kthread+0x15c/0x264
  ret_from_fork+0x10/0x30

Signed-off-by: Mason Zhang <Mason.Zhang at mediatek.com>
---
changes since v2:
* Modified comment after clear doorbell.
  Updated the patch in v3.
changes since v1:
* Remove change id.
---
 drivers/ufs/core/ufshcd.c | 46 ++++++++++++++++++---------------------
 1 file changed, 21 insertions(+), 25 deletions(-)

diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index b1f59a5fe632..6fe51b8d41f9 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -2979,35 +2979,31 @@ static int ufshcd_wait_for_dev_cmd(struct ufs_hba *hba,
 		err = -ETIMEDOUT;
 		dev_dbg(hba->dev, "%s: dev_cmd request timedout, tag %d\n",
 			__func__, lrbp->task_tag);
-		if (ufshcd_clear_cmds(hba, 1U << lrbp->task_tag) == 0) {
+		if (ufshcd_clear_cmds(hba, 1U << lrbp->task_tag) == 0)
 			/* successfully cleared the command, retry if needed */
 			err = -EAGAIN;
+		/*
+		 * in case of an error, after clearing the doorbell,
+		 * we also need to clear the task tag bit from the
+		 * outstanding_reqs variable.
+		 */
+		spin_lock_irqsave(&hba->outstanding_lock, flags);
+		pending = test_bit(lrbp->task_tag,
+				   &hba->outstanding_reqs);
+		if (pending) {
+			hba->dev_cmd.complete = NULL;
+			__clear_bit(lrbp->task_tag,
+				    &hba->outstanding_reqs);
+		}
+		spin_unlock_irqrestore(&hba->outstanding_lock, flags);
+
+		if (!pending) {
 			/*
-			 * Since clearing the command succeeded we also need to
-			 * clear the task tag bit from the outstanding_reqs
-			 * variable.
+			 * The completion handler ran while we tried to
+			 * clear the command.
 			 */
-			spin_lock_irqsave(&hba->outstanding_lock, flags);
-			pending = test_bit(lrbp->task_tag,
-					   &hba->outstanding_reqs);
-			if (pending) {
-				hba->dev_cmd.complete = NULL;
-				__clear_bit(lrbp->task_tag,
-					    &hba->outstanding_reqs);
-			}
-			spin_unlock_irqrestore(&hba->outstanding_lock, flags);
-
-			if (!pending) {
-				/*
-				 * The completion handler ran while we tried to
-				 * clear the command.
-				 */
-				time_left = 1;
-				goto retry;
-			}
-		} else {
-			dev_err(hba->dev, "%s: failed to clear tag %d\n",
-				__func__, lrbp->task_tag);
+			time_left = 1;
+			goto retry;
 		}
 	}
 
-- 
2.18.0