Fix long known deadlock between geom dev destruction and d_close() call.

Use destroy_dev_sched_cb() to not wait for device destruction while holding
GEOM topology lock (that actually caused deadlock).  Use request counting
protected by mutex to properly wait for outstanding requests completion in
cases of device closing and geom destruction.  Unlike r227009, this code
does not block taskqueue thread for indefinite time, waiting for completion.

1 files changed, 129 insertions, 71 deletions

diff --git a/sys/geom/geom_dev.c b/sys/geom/geom_dev.c
index 224b5d6..0a74ee1 100644
--- a/sys/geom/geom_dev.c
+++ b/sys/geom/geom_dev.c
@@ -56,10 +56,13 @@ __FBSDID("$FreeBSD$");
 #include <geom/geom_int.h>
 #include <machine/stdarg.h>
 
-/*
- * Use the consumer private field to reference a physdev alias (if any).
- */
-#define cp_alias_dev	private
+struct g_dev_softc {
+	struct mtx	 sc_mtx;
+	struct cdev	*sc_dev;
+	struct cdev	*sc_alias;
+	int		 sc_open;
+	int		 sc_active;
+};
 
 static d_open_t		g_dev_open;
 static d_close_t	g_dev_close;
@@ -90,6 +93,27 @@ static struct g_class g_dev_class	= {
 	.attrchanged = g_dev_attrchanged
 };
 
+static void
+g_dev_destroy(void *arg, int flags __unused)
+{
+	struct g_consumer *cp;
+	struct g_geom *gp;
+	struct g_dev_softc *sc;
+
+	g_topology_assert();
+	cp = arg;
+	gp = cp->geom;
+	sc = cp->private;
+	g_trace(G_T_TOPOLOGY, "g_dev_destroy(%p(%s))", cp, gp->name);
+	if (cp->acr > 0 || cp->acw > 0 || cp->ace > 0)
+		g_access(cp, -cp->acr, -cp->acw, -cp->ace);
+	g_detach(cp);
+	g_destroy_consumer(cp);
+	g_destroy_geom(gp);
+	mtx_destroy(&sc->sc_mtx);
+	g_free(sc);
+}
+
 void
 g_dev_print(void)
 {
@@ -106,14 +130,16 @@ g_dev_print(void)
 static void
 g_dev_attrchanged(struct g_consumer *cp, const char *attr)
 {
+	struct g_dev_softc *sc;
 	struct cdev *dev;
 	char buf[SPECNAMELEN + 6];
 
+	sc = cp->private;
 	if (strcmp(attr, "GEOM::media") == 0) {
-		dev = cp->geom->softc;
+		dev = sc->sc_dev;
 		snprintf(buf, sizeof(buf), "cdev=%s", dev->si_name);
 		devctl_notify_f("DEVFS", "CDEV", "MEDIACHANGE", buf, M_WAITOK);
-		dev = cp->cp_alias_dev;
+		dev = sc->sc_alias;
 		if (dev != NULL) {
 			snprintf(buf, sizeof(buf), "cdev=%s", dev->si_name);
 			devctl_notify_f("DEVFS", "CDEV", "MEDIACHANGE", buf,
@@ -138,14 +164,14 @@ g_dev_attrchanged(struct g_consumer *cp, const char *attr)
 			struct cdev *old_alias_dev;
 			struct cdev **alias_devp;
 
-			dev = cp->geom->softc;
-			old_alias_dev = cp->cp_alias_dev;
-			alias_devp = (struct cdev **)&cp->cp_alias_dev;
+			dev = sc->sc_dev;
+			old_alias_dev = sc->sc_alias;
+			alias_devp = (struct cdev **)&sc->sc_alias;
 			make_dev_physpath_alias(MAKEDEV_WAITOK, alias_devp,
 			    dev, old_alias_dev, physpath);
-		} else if (cp->cp_alias_dev) {
-			destroy_dev((struct cdev *)cp->cp_alias_dev);
-			cp->cp_alias_dev = NULL;
+		} else if (sc->sc_alias) {
+			destroy_dev((struct cdev *)sc->sc_alias);
+			sc->sc_alias = NULL;
 		}
 		g_free(physpath);
 	}
@@ -170,6 +196,7 @@ g_dev_taste(struct g_class *mp, struct g_provider *pp, int insist __unused)
 {
 	struct g_geom *gp;
 	struct g_consumer *cp;
+	struct g_dev_softc *sc;
 	int error, len;
 	struct cdev *dev, *adev;
 	char buf[64], *val;
@@ -177,7 +204,10 @@ g_dev_taste(struct g_class *mp, struct g_provider *pp, int insist __unused)
 	g_trace(G_T_TOPOLOGY, "dev_taste(%s,%s)", mp->name, pp->name);
 	g_topology_assert();
 	gp = g_new_geomf(mp, "%s", pp->name);
+	sc = g_malloc(sizeof(*sc), M_WAITOK | M_ZERO);
+	mtx_init(&sc->sc_mtx, "g_dev", NULL, MTX_DEF);
 	cp = g_new_consumer(gp);
+	cp->private = sc;
 	error = g_attach(cp, pp);
 	KASSERT(error == 0,
 	    ("g_dev_taste(%s) failed to g_attach, err=%d", pp->name, error));
@@ -189,8 +219,11 @@ g_dev_taste(struct g_class *mp, struct g_provider *pp, int insist __unused)
 		g_detach(cp);
 		g_destroy_consumer(cp);
 		g_destroy_geom(gp);
+		mtx_destroy(&sc->sc_mtx);
+		g_free(sc);
 		return (NULL);
 	}
+	sc->sc_dev = dev;
 
 	/* Search for device alias name and create it if found. */
 	adev = NULL;
@@ -209,12 +242,9 @@ g_dev_taste(struct g_class *mp, struct g_provider *pp, int insist __unused)
 	}
 
 	dev->si_iosize_max = MAXPHYS;
-	gp->softc = dev;
-	dev->si_drv1 = gp;
 	dev->si_drv2 = cp;
 	if (adev != NULL) {
 		adev->si_iosize_max = MAXPHYS;
-		adev->si_drv1 = gp;
 		adev->si_drv2 = cp;
 	}
 
@@ -226,17 +256,15 @@ g_dev_taste(struct g_class *mp, struct g_provider *pp, int insist __unused)
 static int
 g_dev_open(struct cdev *dev, int flags, int fmt, struct thread *td)
 {
-	struct g_geom *gp;
 	struct g_consumer *cp;
+	struct g_dev_softc *sc;
 	int error, r, w, e;
 
-	gp = dev->si_drv1;
 	cp = dev->si_drv2;
-	if (gp == NULL || cp == NULL || gp->softc != dev)
+	if (cp == NULL)
 		return(ENXIO);		/* g_dev_taste() not done yet */
-
 	g_trace(G_T_ACCESS, "g_dev_open(%s, %d, %d, %p)",
-	    gp->name, flags, fmt, td);
+	    cp->geom->name, flags, fmt, td);
 
 	r = flags & FREAD ? 1 : 0;
 	w = flags & FWRITE ? 1 : 0;
@@ -255,27 +283,32 @@ g_dev_open(struct cdev *dev, int flags, int fmt, struct thread *td)
 			return (error);
 	}
 	g_topology_lock();
-	if (dev->si_devsw == NULL)
-		error = ENXIO;		/* We were orphaned */
-	else
-		error = g_access(cp, r, w, e);
+	error = g_access(cp, r, w, e);
 	g_topology_unlock();
+	if (error == 0) {
+		sc = cp->private;
+		mtx_lock(&sc->sc_mtx);
+		if (sc->sc_open == 0 && sc->sc_active != 0)
+			wakeup(&sc->sc_active);
+		sc->sc_open += r + w + e;
+		mtx_unlock(&sc->sc_mtx);
+	}
 	return(error);
 }
 
 static int
 g_dev_close(struct cdev *dev, int flags, int fmt, struct thread *td)
 {
-	struct g_geom *gp;
 	struct g_consumer *cp;
-	int error, r, w, e, i;
+	struct g_dev_softc *sc;
+	int error, r, w, e;
 
-	gp = dev->si_drv1;
 	cp = dev->si_drv2;
-	if (gp == NULL || cp == NULL)
+	if (cp == NULL)
 		return(ENXIO);
 	g_trace(G_T_ACCESS, "g_dev_close(%s, %d, %d, %p)",
-	    gp->name, flags, fmt, td);
+	    cp->geom->name, flags, fmt, td);
+	
 	r = flags & FREAD ? -1 : 0;
 	w = flags & FWRITE ? -1 : 0;
 #ifdef notyet
@@ -283,25 +316,14 @@ g_dev_close(struct cdev *dev, int flags, int fmt, struct thread *td)
 #else
 	e = 0;
 #endif
+	sc = cp->private;
+	mtx_lock(&sc->sc_mtx);
+	sc->sc_open += r + w + e;
+	while (sc->sc_open == 0 && sc->sc_active != 0)
+		msleep(&sc->sc_active, &sc->sc_mtx, 0, "PRIBIO", 0);
+	mtx_unlock(&sc->sc_mtx);
 	g_topology_lock();
-	if (dev->si_devsw == NULL)
-		error = ENXIO;		/* We were orphaned */
-	else
-		error = g_access(cp, r, w, e);
-	for (i = 0; i < 10 * hz;) {
-		if (cp->acr != 0 || cp->acw != 0)
-			break;
- 		if (cp->nstart == cp->nend)
-			break;
-		pause("gdevwclose", hz / 10);
-		i += hz / 10;
-	}
-	if (cp->acr == 0 && cp->acw == 0 && cp->nstart != cp->nend) {
-		printf("WARNING: Final close of geom_dev(%s) %s %s\n",
-		    gp->name,
-		    "still has outstanding I/O after 10 seconds.",
-		    "Completing close anyway, panic may happen later.");
-	}
+	error = g_access(cp, r, w, e);
 	g_topology_unlock();
 	return (error);
 }
@@ -315,7 +337,6 @@ g_dev_close(struct cdev *dev, int flags, int fmt, struct thread *td)
 static int
 g_dev_ioctl(struct cdev *dev, u_long cmd, caddr_t data, int fflag, struct thread *td)
 {
-	struct g_geom *gp;
 	struct g_consumer *cp;
 	struct g_provider *pp;
 	struct g_kerneldump kd;
@@ -323,7 +344,6 @@ g_dev_ioctl(struct cdev *dev, u_long cmd, caddr_t data, int fflag, struct thread
 	int i, error;
 	u_int u;
 
-	gp = dev->si_drv1;
 	cp = dev->si_drv2;
 	pp = cp->provider;
 
@@ -437,8 +457,13 @@ g_dev_ioctl(struct cdev *dev, u_long cmd, caddr_t data, int fflag, struct thread
 static void
 g_dev_done(struct bio *bp2)
 {
+	struct g_consumer *cp;
+	struct g_dev_softc *sc;
 	struct bio *bp;
+	int destroy;
 
+	cp = bp2->bio_from;
+	sc = cp->private;
 	bp = bp2->bio_parent;
 	bp->bio_error = bp2->bio_error;
 	if (bp->bio_error != 0) {
@@ -452,6 +477,17 @@ g_dev_done(struct bio *bp2)
 	bp->bio_resid = bp->bio_length - bp2->bio_completed;
 	bp->bio_completed = bp2->bio_completed;
 	g_destroy_bio(bp2);
+	destroy = 0;
+	mtx_lock(&sc->sc_mtx);
+	if ((--sc->sc_active) == 0) {
+		if (sc->sc_open == 0)
+			wakeup(&sc->sc_active);
+		if (sc->sc_dev == NULL)
+			destroy = 1;
+	}
+	mtx_unlock(&sc->sc_mtx);
+	if (destroy)
+		g_post_event(g_dev_destroy, cp, M_WAITOK, NULL);
 	biodone(bp);
 }
 
@@ -461,6 +497,7 @@ g_dev_strategy(struct bio *bp)
 	struct g_consumer *cp;
 	struct bio *bp2;
 	struct cdev *dev;
+	struct g_dev_softc *sc;
 
 	KASSERT(bp->bio_cmd == BIO_READ ||
 	        bp->bio_cmd == BIO_WRITE ||
@@ -468,6 +505,7 @@ g_dev_strategy(struct bio *bp)
 		("Wrong bio_cmd bio=%p cmd=%d", bp, bp->bio_cmd));
 	dev = bp->bio_dev;
 	cp = dev->si_drv2;
+	sc = cp->private;
 	KASSERT(cp->acr || cp->acw,
 	    ("Consumer with zero access count in g_dev_strategy"));
 #ifdef INVARIANTS
@@ -478,6 +516,11 @@ g_dev_strategy(struct bio *bp)
 		return;
 	}
 #endif
+	mtx_lock(&sc->sc_mtx);
+	KASSERT(sc->sc_open > 0, ("Closed device in g_dev_strategy"));
+	sc->sc_active++;
+	mtx_unlock(&sc->sc_mtx);
+
 	for (;;) {
 		/*
 		 * XXX: This is not an ideal solution, but I belive it to
@@ -501,46 +544,61 @@ g_dev_strategy(struct bio *bp)
 }
 
 /*
+ * g_dev_callback()
+ *
+ * Called by devfs when asynchronous device destruction is completed.
+ * - Mark that we have no attached device any more.
+ * - If there are no outstanding requests, schedule geom destruction.
+ *   Otherwise destruction will be scheduled later by g_dev_done().
+ */
+
+static void
+g_dev_callback(void *arg)
+{
+	struct g_consumer *cp;
+	struct g_dev_softc *sc;
+	int destroy;
+
+	cp = arg;
+	sc = cp->private;
+	g_trace(G_T_TOPOLOGY, "g_dev_callback(%p(%s))", cp, cp->geom->name);
+
+	mtx_lock(&sc->sc_mtx);
+	sc->sc_dev = NULL;
+	sc->sc_alias = NULL;
+	destroy = (sc->sc_active == 0);
+	mtx_unlock(&sc->sc_mtx);
+	if (destroy)
+		g_post_event(g_dev_destroy, cp, M_WAITOK, NULL);
+}
+
+/*
  * g_dev_orphan()
  *
  * Called from below when the provider orphaned us.
  * - Clear any dump settings.
- * - Destroy the struct cdev to prevent any more request from coming in.  The
- *   provider is already marked with an error, so anything which comes in
- *   in the interrim will be returned immediately.
- * - Wait for any outstanding I/O to finish.
- * - Set our access counts to zero, whatever they were.
- * - Detach and self-destruct.
+ * - Request asynchronous device destruction to prevent any more requests
+ *   from coming in.  The provider is already marked with an error, so
+ *   anything which comes in in the interrim will be returned immediately.
  */
 
 static void
 g_dev_orphan(struct g_consumer *cp)
 {
-	struct g_geom *gp;
 	struct cdev *dev;
+	struct g_dev_softc *sc;
 
 	g_topology_assert();
-	gp = cp->geom;
-	dev = gp->softc;
-	g_trace(G_T_TOPOLOGY, "g_dev_orphan(%p(%s))", cp, gp->name);
+	sc = cp->private;
+	dev = sc->sc_dev;
+	g_trace(G_T_TOPOLOGY, "g_dev_orphan(%p(%s))", cp, cp->geom->name);
 
 	/* Reset any dump-area set on this device */
 	if (dev->si_flags & SI_DUMPDEV)
 		set_dumper(NULL, NULL);
 
 	/* Destroy the struct cdev *so we get no more requests */
-	destroy_dev(dev);
-
-	/* Wait for the cows to come home */
-	while (cp->nstart != cp->nend)
-		pause("gdevorphan", hz / 10);
-
-	if (cp->acr > 0 || cp->acw > 0 || cp->ace > 0)
-		g_access(cp, -cp->acr, -cp->acw, -cp->ace);
-
-	g_detach(cp);
-	g_destroy_consumer(cp);
-	g_destroy_geom(gp);
+	destroy_dev_sched_cb(dev, g_dev_callback, cp);
 }
 
 DECLARE_GEOM_CLASS(g_dev_class, g_dev);