[PATCH v4 1/1] scsi: ufs: core: fix device management cmd timeout flow

[Mason Zhang <mason.zhang@mediatek.com>]

From: Mason Zhang <Mason.Zhang@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@mediatek.com>
---
Changes since v3:
* Not clear outstanding_reqs if clear cmds fail.
  Updated the patch in v4.
Changes since v2:
* Modified comment after clear doorbell.
Changes since v1:
* Remove change id.
---
 drivers/ufs/core/ufshcd.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index b1f59a5fe632..fa86ce80f350 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -3008,6 +3008,22 @@ static int ufshcd_wait_for_dev_cmd(struct ufs_hba *hba,
 		} else {
 			dev_err(hba->dev, "%s: failed to clear tag %d\n",
 				__func__, lrbp->task_tag);
+
+			spin_lock_irqsave(&hba->outstanding_lock, flags);
+			pending = test_bit(lrbp->task_tag,
+					   &hba->outstanding_reqs);
+			if (pending)
+				hba->dev_cmd.complete = NULL;
+			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;
+			}
 		}
 	}
 
-- 
2.18.0