svn commit: r256188 - head/sys/cam

[Alexander Motin]

Author: mav
Date: Wed Oct  9 12:09:01 2013
New Revision: 256188
URL: http://svnweb.freebsd.org/changeset/base/256188

Log:
  Close the race on path ID allocation in xpt_bus_register() if two buses are
  registered simultaneously. Due to topology unlock between the ID allocation
  and the bus registration there is a chance that two buses may get the
  same IDs. That is supposed reason of lock assertion panic in CAM during
  initial bus scanning after new iscsid initiates two sessions same time.
  
  Reported by:	trasz
  Approved by:	re (glebus, marius)
  MFC after:	2 weeks

Modified:
  head/sys/cam/cam_xpt.c

Modified: head/sys/cam/cam_xpt.c
==============================================================================
--- head/sys/cam/cam_xpt.c	Wed Oct  9 12:03:04 2013	(r256187)
+++ head/sys/cam/cam_xpt.c	Wed Oct  9 12:09:01 2013	(r256188)
@@ -2415,7 +2415,7 @@ xptsetasyncbusfunc(struct cam_eb *bus, v
 	struct ccb_setasync *csa = (struct ccb_setasync *)arg;
 
 	xpt_compile_path(&path, /*periph*/NULL,
-			 bus->sim->path_id,
+			 bus->path_id,
 			 CAM_TARGET_WILDCARD,
 			 CAM_LUN_WILDCARD);
 	xpt_setup_ccb(&cpi.ccb_h, &path, CAM_PRIORITY_NORMAL);
@@ -3840,13 +3840,8 @@ xpt_bus_register(struct cam_sim *sim, de
 		/* Couldn't satisfy request */
 		return (CAM_RESRC_UNAVAIL);
 	}
-	if (strcmp(sim->sim_name, "xpt") != 0) {
-		sim->path_id =
-		    xptpathid(sim->sim_name, sim->unit_number, sim->bus_id);
-	}
 
 	TAILQ_INIT(&new_bus->et_entries);
-	new_bus->path_id = sim->path_id;
 	cam_sim_hold(sim);
 	new_bus->sim = sim;
 	timevalclear(&new_bus->last_reset);
@@ -3855,6 +3850,8 @@ xpt_bus_register(struct cam_sim *sim, de
 	new_bus->generation = 0;
 
 	xpt_lock_buses();
+	sim->path_id = new_bus->path_id =
+	    xptpathid(sim->sim_name, sim->unit_number, sim->bus_id);
 	old_bus = TAILQ_FIRST(&xsoftc.xpt_busses);
 	while (old_bus != NULL
 	    && old_bus->path_id < new_bus->path_id)
@@ -3958,8 +3955,8 @@ xptnextfreepathid(void)
 	path_id_t pathid;
 	const char *strval;
 
+	mtx_assert(&xsoftc.xpt_topo_lock, MA_OWNED);
 	pathid = 0;
-	xpt_lock_buses();
 	bus = TAILQ_FIRST(&xsoftc.xpt_busses);
 retry:
 	/* Find an unoccupied pathid */
@@ -3968,7 +3965,6 @@ retry:
 			pathid++;
 		bus = TAILQ_NEXT(bus, links);
 	}
-	xpt_unlock_buses();
 
 	/*
 	 * Ensure that this pathid is not reserved for
@@ -3977,7 +3973,6 @@ retry:
 	if (resource_string_value("scbus", pathid, "at", &strval) == 0) {
 		++pathid;
 		/* Start the search over */
-		xpt_lock_buses();
 		goto retry;
 	}
 	return (pathid);
@@ -3993,6 +3988,8 @@ xptpathid(const char *sim_name, int sim_
 
 	pathid = CAM_XPT_PATH_ID;
 	snprintf(buf, sizeof(buf), "%s%d", sim_name, sim_unit);
+	if (strcmp(buf, "xpt0") == 0 && sim_bus == 0)
+		return (pathid);
 	i = 0;
 	while ((resource_find_match(&i, &dname, &dunit, "at", buf)) == 0) {
 		if (strcmp(dname, "scbus")) {