MFC r279554:

Make periphdriver_register() take XPT lock when modifying the periph_drivers
array.

This fixes a panic that sometimes occured when kldloading ctl.ko.

PR:		200384
Sponsored by:	The FreeBSD Foundation

1 files changed, 12 insertions, 1 deletions

diff --git a/sys/cam/cam_periph.c b/sys/cam/cam_periph.c
index 2544d27..53454f8 100644
--- a/sys/cam/cam_periph.c
+++ b/sys/cam/cam_periph.c
@@ -108,9 +108,19 @@ periphdriver_register(void *data)
 	struct periph_driver **newdrivers, **old;
 	int ndrivers;
 
+again:
 	ndrivers = nperiph_drivers + 2;
 	newdrivers = malloc(sizeof(*newdrivers) * ndrivers, M_CAMPERIPH,
 			    M_WAITOK);
+	xpt_lock_buses();
+	if (ndrivers != nperiph_drivers + 2) {
+		/*
+		 * Lost race against itself; go around.
+		 */
+		xpt_unlock_buses();
+		free(newdrivers, M_CAMPERIPH);
+		goto again;
+	}
 	if (periph_drivers)
 		bcopy(periph_drivers, newdrivers,
 		      sizeof(*newdrivers) * nperiph_drivers);
@@ -118,9 +128,10 @@ periphdriver_register(void *data)
 	newdrivers[nperiph_drivers + 1] = NULL;
 	old = periph_drivers;
 	periph_drivers = newdrivers;
+	nperiph_drivers++;
+	xpt_unlock_buses();
 	if (old)
 		free(old, M_CAMPERIPH);
-	nperiph_drivers++;
 	/* If driver marked as early or it is late now, initialize it. */
 	if (((drv->flags & CAM_PERIPH_DRV_EARLY) != 0 && initialized > 0) ||
 	    initialized > 1)