[PATCH V2] scsi: ufs: core: Fix synchronization between scsi_unjam_host() and ufshcd_queuecommand()

[Adrian Hunter <adrian.hunter@intel.com>]

The SCSI error handler calls scsi_unjam_host() which can call the queue
function ufshcd_queuecommand() indirectly. The error handler changes the
state to UFSHCD_STATE_RESET while running, but error interrupts that
happen while the error handler is running could change the state to
UFSHCD_STATE_EH_SCHEDULED_NON_FATAL which would allow requests to go
through ufshcd_queuecommand() even though the error handler is running.
Block that hole by checking whether the error handler is in progress.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---

Changes in V2:

	Add comment

 drivers/scsi/ufs/ufshcd.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index f34227add27d..29d202207b18 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -2688,7 +2688,19 @@ static int ufshcd_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *cmd)
 
 	switch (hba->ufshcd_state) {
 	case UFSHCD_STATE_OPERATIONAL:
+		break;
 	case UFSHCD_STATE_EH_SCHEDULED_NON_FATAL:
+		/*
+		 * SCSI error handler can call ->queuecommand() while UFS error
+		 * handler is in progress. Error interrupts could change the
+		 * state from UFSHCD_STATE_RESET to
+		 * UFSHCD_STATE_EH_SCHEDULED_NON_FATAL. Prevent requests
+		 * being issued in that case.
+		 */
+		if (ufshcd_eh_in_progress(hba)) {
+			err = SCSI_MLQUEUE_HOST_BUSY;
+			goto out;
+		}
 		break;
 	case UFSHCD_STATE_EH_SCHEDULED_FATAL:
 		/*
-- 
2.25.1