MFC r321207:

  ------------------------------------------------------------------------
  r321207 | ken | 2017-07-19 09:39:01 -0600 (Wed, 19 Jul 2017) | 14 lines

  Fix spurious timeouts on commands sent to mps(4) and mpr(4) controllers.

  mps_wait_command() and mpr_wait_command() were using getmicrotime() to
  determine elapsed time when checking for a timeout in polled mode.
  getmicrotime() isn't guaranteed to monotonically increase, and that
  caused spurious timeouts occasionally.

  Switch to using getmicrouptime(), which does increase monotonically.
  This fixes the spurious timeouts in my test case.

  ------------------------------------------------------------------------
Reviewed by:	slm, scottl
Sponsored by:	Spectra Logic

2 files changed, 30 insertions, 8 deletions

diff --git a/sys/dev/mpr/mpr.c b/sys/dev/mpr/mpr.c
index ed5b25b..72edf46 100644
--- a/sys/dev/mpr/mpr.c
+++ b/sys/dev/mpr/mpr.c
@@ -3286,9 +3286,17 @@ mpr_wait_command(struct mpr_softc *sc, struct mpr_command *cm, int timeout,
 	if (curthread->td_pflags & TDP_NOSLEEPING)
 #endif //__FreeBSD_version >= 1000029
 		sleep_flag = NO_SLEEP;
-	getmicrotime(&start_time);
+	getmicrouptime(&start_time);
 	if (mtx_owned(&sc->mpr_mtx) && sleep_flag == CAN_SLEEP) {
 		error = msleep(cm, &sc->mpr_mtx, 0, "mprwait", timeout*hz);
+		if (error == EWOULDBLOCK) {
+			/*
+			 * Record the actual elapsed time in the case of a
+			 * timeout for the message below.
+			 */
+			getmicrouptime(&cur_time);
+			timevalsub(&cur_time, &start_time);
+		}
 	} else {
 		while ((cm->cm_flags & MPR_CM_FLAGS_COMPLETE) == 0) {
 			mpr_intr_locked(sc);
@@ -3297,8 +3305,9 @@ mpr_wait_command(struct mpr_softc *sc, struct mpr_command *cm, int timeout,
 			else
 				DELAY(50000);
 		
-			getmicrotime(&cur_time);
-			if ((cur_time.tv_sec - start_time.tv_sec) > timeout) {
+			getmicrouptime(&cur_time);
+			timevalsub(&cur_time, &start_time);
+			if (cur_time.tv_sec > timeout) {
 				error = EWOULDBLOCK;
 				break;
 			}
@@ -3306,7 +3315,9 @@ mpr_wait_command(struct mpr_softc *sc, struct mpr_command *cm, int timeout,
 	}
 
 	if (error == EWOULDBLOCK) {
-		mpr_dprint(sc, MPR_FAULT, "Calling Reinit from %s\n", __func__);
+		mpr_dprint(sc, MPR_FAULT, "Calling Reinit from %s, timeout=%d,"
+		    " elapsed=%jd\n", __func__, timeout,
+		    (intmax_t)cur_time.tv_sec);
 		rc = mpr_reinit(sc);
 		mpr_dprint(sc, MPR_FAULT, "Reinit %s\n", (rc == 0) ? "success" :
 		    "failed");
diff --git a/sys/dev/mps/mps.c b/sys/dev/mps/mps.c
index 9ec80ad..357c87f 100644
--- a/sys/dev/mps/mps.c
+++ b/sys/dev/mps/mps.c
@@ -2551,10 +2551,18 @@ mps_wait_command(struct mps_softc *sc, struct mps_command *cm, int timeout,
 	 */
 	if (curthread->td_no_sleeping != 0)
 		sleep_flag = NO_SLEEP;
-	getmicrotime(&start_time);
+	getmicrouptime(&start_time);
 	if (mtx_owned(&sc->mps_mtx) && sleep_flag == CAN_SLEEP) {
 		cm->cm_flags |= MPS_CM_FLAGS_WAKEUP;
 		error = msleep(cm, &sc->mps_mtx, 0, "mpswait", timeout*hz);
+		if (error == EWOULDBLOCK) {
+			/*
+			 * Record the actual elapsed time in the case of a
+			 * timeout for the message below.
+			 */
+			getmicrouptime(&cur_time);
+			timevalsub(&cur_time, &start_time);
+		}
 	} else {
 		while ((cm->cm_flags & MPS_CM_FLAGS_COMPLETE) == 0) {
 			mps_intr_locked(sc);
@@ -2563,8 +2571,9 @@ mps_wait_command(struct mps_softc *sc, struct mps_command *cm, int timeout,
 			else
 				DELAY(50000);
 		
-			getmicrotime(&cur_time);
-			if ((cur_time.tv_sec - start_time.tv_sec) > timeout) {
+			getmicrouptime(&cur_time);
+			timevalsub(&cur_time, &start_time);
+			if (cur_time.tv_sec > timeout) {
 				error = EWOULDBLOCK;
 				break;
 			}
@@ -2572,7 +2581,9 @@ mps_wait_command(struct mps_softc *sc, struct mps_command *cm, int timeout,
 	}
 
 	if (error == EWOULDBLOCK) {
-		mps_dprint(sc, MPS_FAULT, "Calling Reinit from %s\n", __func__);
+		mps_dprint(sc, MPS_FAULT, "Calling Reinit from %s, timeout=%d,"
+		    " elapsed=%jd\n", __func__, timeout,
+		    (intmax_t)cur_time.tv_sec);
 		rc = mps_reinit(sc);
 		mps_dprint(sc, MPS_FAULT, "Reinit %s\n", (rc == 0) ? "success" :
 		    "failed");