diff --git a/share/man/man9/malloc.9 b/share/man/man9/malloc.9
index a2978af3a802..eec2c8691029 100644
--- a/share/man/man9/malloc.9
+++ b/share/man/man9/malloc.9
@@ -29,7 +29,7 @@
 .\" $NetBSD: malloc.9,v 1.3 1996/11/11 00:05:11 lukem Exp $
 .\" $FreeBSD$
 .\"
-.Dd January 16, 2014
+.Dd November 19, 2015
 .Dt MALLOC 9
 .Os
 .Sh NAME
@@ -227,6 +227,13 @@ may sleep when called with
 .Dv M_WAITOK .
 .Fn free
 never sleeps.
+However,
+.Fn malloc ,
+.Fn realloc,
+.Fn reallocf
+and
+.Fn free
+may not be called in a critical section or while holding a spin lock.
 .Pp
 Any calls to
 .Fn malloc
diff --git a/sys/kern/kern_malloc.c b/sys/kern/kern_malloc.c
index ff5b106e385e..01aff78a37e6 100644
--- a/sys/kern/kern_malloc.c
+++ b/sys/kern/kern_malloc.c
@@ -476,6 +476,9 @@ malloc(unsigned long size, struct malloc_type *mtp, int flags)
 		KASSERT(curthread->td_intr_nesting_level == 0,
 		   ("malloc(M_WAITOK) in interrupt context"));
 
+	KASSERT(curthread->td_critnest == 0,
+	    ("malloc: called with spinlock or critical section held"));
+
 #ifdef DEBUG_MEMGUARD
 	if (memguard_cmp_mtp(mtp, size)) {
 		va = memguard_alloc(size, flags);
@@ -542,6 +545,9 @@ free(void *addr, struct malloc_type *mtp)
 
 	KASSERT(mtp->ks_magic == M_MAGIC, ("free: bad malloc type magic"));
 
+	KASSERT(curthread->td_critnest == 0,
+	    ("free: called with spinlock or critical section held"));
+
 	/* free(NULL, ...) does nothing */
 	if (addr == NULL)
 		return;
@@ -605,6 +611,9 @@ realloc(void *addr, unsigned long size, struct malloc_type *mtp, int flags)
 	KASSERT(mtp->ks_magic == M_MAGIC,
 	    ("realloc: bad malloc type magic"));
 
+	KASSERT(curthread->td_critnest == 0,
+	    ("realloc: called with spinlock or critical section held"));
+
 	/* realloc(NULL, ...) is equivalent to malloc(...) */
 	if (addr == NULL)
 		return (malloc(size, mtp, flags));
diff --git a/sys/vm/uma_core.c b/sys/vm/uma_core.c
index 8169256994dc..1f57dfff898c 100644
--- a/sys/vm/uma_core.c
+++ b/sys/vm/uma_core.c
@@ -2149,6 +2149,10 @@ uma_zalloc_arg(uma_zone_t zone, void *udata, int flags)
 		WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
 		    "uma_zalloc_arg: zone \"%s\"", zone->uz_name);
 	}
+
+	KASSERT(curthread->td_critnest == 0,
+	    ("uma_zalloc_arg: called with spinlock or critical section held"));
+
 #ifdef DEBUG_MEMGUARD
 	if (memguard_cmp_zone(zone)) {
 		item = memguard_alloc(zone->uz_size, flags);
@@ -2686,6 +2690,9 @@ uma_zfree_arg(uma_zone_t zone, void *item, void *udata)
 	CTR2(KTR_UMA, "uma_zfree_arg thread %x zone %s", curthread,
 	    zone->uz_name);
 
+	KASSERT(curthread->td_critnest == 0,
+	    ("uma_zfree_arg: called with spinlock or critical section held"));
+
         /* uma_zfree(..., NULL) does nothing, to match free(9). */
         if (item == NULL)
                 return;