Index: sys/kern/imgact_binmisc.c
===================================================================
--- sys/kern/imgact_binmisc.c
+++ sys/kern/imgact_binmisc.c
@@ -98,68 +98,11 @@
 	SLIST_HEAD_INITIALIZER(interpreter_list);
 
 static int interp_list_entry_count = 0;
-static int interp_list_rcount = 0;
-static struct mtx interp_list_mtx;
 
-int imgact_binmisc_exec(struct image_params *imgp);
-
-static inline void
-interp_list_rlock()
-{
-
-    /* Don't use atomic_add() here.  We must block if the mutex is held. */
-    mtx_lock(&interp_list_mtx);
-    interp_list_rcount++;
-    mtx_unlock(&interp_list_mtx);
-}
-
-static inline void
-interp_list_runlock()
-{
-
-    /* Decrement the reader count and wake up one writer, if any. */
-    atomic_subtract_int(&interp_list_rcount, 1);
-    if (interp_list_rcount == 0)
-        wakeup_one(&interp_list_rcount);
-}
+static struct sx interp_list_sx;
 
-static inline void
-interp_list_wlock()
-{
-
-    /* Wait until there are no readers. */
-    mtx_lock(&interp_list_mtx);
-    while (interp_list_rcount)
-        mtx_sleep(&interp_list_rcount, &interp_list_mtx, 0, "IABM", 0);
-}
-
-static inline void
-interp_list_wunlock()
-{
-
-    mtx_unlock(&interp_list_mtx);
-}
-
-#define interp_list_assert_rlocked()					  \
-	KASSERT(interp_list_rcount > 0, ("%s: interp_list lock not held " \
-					"for read", __func__))
-
-#define	interp_list_assert_wlocked() mtx_assert(&interp_list_mtx, MA_OWNED)
-
-#ifdef INVARIANTS
-#define	interp_list_assert_locked()	do {				\
-	if (interp_list_rcount == 0) 					\
-		mtx_assert(&interp_list_mtx, MA_OWNED);			\
-	else 								\
-		KASSERT(interp_list_rcount > 0,				\
-			("%s: interp_list lock not held", __func__));	\
-} while(0)
-
-#else /* ! INVARIANTS */
+int imgact_binmisc_exec(struct image_params *imgp);
 
-#define	interp_list_assert_locked()	do {				\
-} while(0)
-#endif /* ! INVARIANTS */
 
 /*
  * Populate the entry with the information about the interpreter.
@@ -261,7 +204,7 @@
 {
 	imgact_binmisc_entry_t *ibe;
 
-	interp_list_assert_locked();
+	sx_assert(&interp_list_sx, SA_LOCKED);
 
 	SLIST_FOREACH(ibe, &interpreter_list, link) {
 		if (strncmp(name, ibe->ibe_name, IBE_NAME_MAX) == 0)
@@ -323,16 +266,16 @@
 	if (!ibe)
 		return (ENOMEM);
 
-	interp_list_wlock();
+	sx_xlock(&interp_list_sx);
 	if (imgact_binmisc_find_entry(xbe->xbe_name) != NULL) {
-		interp_list_wunlock();
+		sx_xunlock(&interp_list_sx);
 		imgact_binmisc_destroy_entry(ibe);
 		return (EEXIST);
 	}
 
 	SLIST_INSERT_HEAD(&interpreter_list, ibe, link);
 	interp_list_entry_count++;
-	interp_list_wunlock();
+	sx_xunlock(&interp_list_sx);
 
 	return (0);
 }
@@ -346,14 +289,14 @@
 {
 	imgact_binmisc_entry_t *ibe;
 
-	interp_list_wlock();
+	sx_xlock(&interp_list_sx);
 	if ((ibe = imgact_binmisc_find_entry(name)) == NULL) {
-		interp_list_wunlock();
+		sx_xunlock(&interp_list_sx);
 		return (ENOENT);
 	}
 	SLIST_REMOVE(&interpreter_list, ibe, imgact_binmisc_entry, link);
 	interp_list_entry_count--;
-	interp_list_wunlock();
+	sx_xunlock(&interp_list_sx);
 
 	imgact_binmisc_destroy_entry(ibe);
 
@@ -369,14 +312,14 @@
 {
 	imgact_binmisc_entry_t *ibe;
 
-	interp_list_rlock();
+	sx_slock(&interp_list_sx);
 	if ((ibe = imgact_binmisc_find_entry(name)) == NULL) {
-		interp_list_runlock();
+		sx_sunlock(&interp_list_sx);
 		return (ENOENT);
 	}
 
 	atomic_clear_32(&ibe->ibe_flags, IBF_ENABLED);
-	interp_list_runlock();
+	sx_sunlock(&interp_list_sx);
 
 	return (0);
 }
@@ -390,14 +333,14 @@
 {
 	imgact_binmisc_entry_t *ibe;
 
-	interp_list_rlock();
+	sx_slock(&interp_list_sx);
 	if ((ibe = imgact_binmisc_find_entry(name)) == NULL) {
-		interp_list_runlock();
+		sx_sunlock(&interp_list_sx);
 		return (ENOENT);
 	}
 
 	atomic_set_32(&ibe->ibe_flags, IBF_ENABLED);
-	interp_list_runlock();
+	sx_sunlock(&interp_list_sx);
 
 	return (0);
 }
@@ -408,7 +351,7 @@
 {
 	uint32_t i;
 
-	interp_list_assert_rlocked();
+	sx_assert(&interp_list_sx, SA_LOCKED);
 
 	memset(xbe, 0, sizeof(*xbe));
 	strlcpy(xbe->xbe_name, ibe->ibe_name, IBE_NAME_MAX);
@@ -440,14 +383,14 @@
 	imgact_binmisc_entry_t *ibe;
 	int error = 0;
 
-	interp_list_rlock();
+	sx_slock(&interp_list_sx);
 	if ((ibe = imgact_binmisc_find_entry(name)) == NULL) {
-		interp_list_runlock();
+		sx_sunlock(&interp_list_sx);
 		return (ENOENT);
 	}
 
 	error = imgact_binmisc_populate_xbe(xbe, ibe);
-	interp_list_runlock();
+	sx_sunlock(&interp_list_sx);
 
 	return (error);
 }
@@ -462,12 +405,12 @@
 	imgact_binmisc_entry_t *ibe;
 	int error = 0, count;
 
-	interp_list_rlock();
+	sx_slock(&interp_list_sx);
 	count = interp_list_entry_count;
 	/* Don't block in malloc() while holding lock. */
 	xbe = malloc(sizeof(*xbe) * count, M_BINMISC, M_NOWAIT|M_ZERO);
 	if (!xbe) {
-		interp_list_runlock();
+		sx_sunlock(&interp_list_sx);
 		return (ENOMEM);
 	}
 
@@ -477,7 +420,7 @@
 		if (error)
 			break;
 	}
-	interp_list_runlock();
+	sx_sunlock(&interp_list_sx);
 
 	if (!error)
 		error = SYSCTL_OUT(req, xbe, sizeof(*xbe) * count);
@@ -614,7 +557,7 @@
 	int i;
 	size_t sz;
 
-	interp_list_assert_rlocked();
+	sx_assert(&interp_list_sx, SA_LOCKED);
 
 	SLIST_FOREACH(ibe, &interpreter_list, link) {
 		if (!(IBF_ENABLED & ibe->ibe_flags))
@@ -651,15 +594,15 @@
 	char *s, *d;
 
 	/* Do we have an interpreter for the given image header? */
-	interp_list_rlock();
+	sx_slock(&interp_list_sx);
 	if ((ibe = imgact_binmisc_find_interpreter(image_header)) == NULL) {
-		interp_list_runlock();
+		sx_sunlock(&interp_list_sx);
 		return (-1);
 	}
 
 	/* No interpreter nesting allowed. */
 	if (imgp->interpreted & IMGACT_BINMISC) {
-		interp_list_runlock();
+		sx_sunlock(&interp_list_sx);
 		return (ENOEXEC);
 	}
 
@@ -707,7 +650,7 @@
 
 		default:
 			/* Hmm... This shouldn't happen. */
-			interp_list_runlock();
+			sx_sunlock(&interp_list_sx);
 			printf("%s: Unknown macro #%c sequence in "
 			    "interpreter string\n", KMOD_NAME, *(s + 1));
 			error = EINVAL;
@@ -718,15 +661,12 @@
 
 	/* Check to make sure we won't overrun the stringspace. */
 	if (offset > imgp->args->stringspace) {
-		interp_list_runlock();
+		sx_sunlock(&interp_list_sx);
 		error = E2BIG;
 		goto done;
 	}
 
-	/*
-	 * Make room for the interpreter. Doing an overlapping copy so
-	 * bcopy() must be used.
-	 */
+	/* Make room for the interpreter */
 	bcopy(imgp->args->begin_argv, imgp->args->begin_argv + offset,
 	    imgp->args->endp - imgp->args->begin_argv);
 
@@ -781,7 +721,7 @@
 		s++;
 	}
 	*d = '\0';
-	interp_list_runlock();
+	sx_sunlock(&interp_list_sx);
 
 	if (!error)
 		imgp->interpreter_name = imgp->args->begin_argv;
@@ -797,7 +737,7 @@
 imgact_binmisc_init(void *arg)
 {
 
-	mtx_init(&interp_list_mtx, KMOD_NAME, NULL, MTX_DEF);
+	sx_init(&interp_list_sx, KMOD_NAME);
 }
 
 static void
@@ -806,15 +746,15 @@
 	imgact_binmisc_entry_t *ibe, *ibe_tmp;
 
 	/* Free all the interpreters. */
-	interp_list_wlock();
+	sx_xlock(&interp_list_sx);
 	SLIST_FOREACH_SAFE(ibe, &interpreter_list, link, ibe_tmp) {
 		SLIST_REMOVE(&interpreter_list, ibe, imgact_binmisc_entry,
 		    link);
 		imgact_binmisc_destroy_entry(ibe);
 	}
-	interp_list_wunlock();
+	sx_xunlock(&interp_list_sx);
 
-	mtx_destroy(&interp_list_mtx);
+	sx_destroy(&interp_list_sx);
 }
 
 SYSINIT(imgact_binmisc, SI_SUB_EXEC, SI_ORDER_MIDDLE, imgact_binmisc_init, 0);