Index: sys/kern/kern_malloc.c
===================================================================
--- sys/kern/kern_malloc.c
+++ sys/kern/kern_malloc.c
@@ -618,6 +618,9 @@
 	unsigned long osize = size;
 #endif
 
+	KASSERT((flags & M_WAITOK) == 0 || THREAD_CAN_SLEEP(),
+	    ("malloc(M_WAITOK) in non-sleepable context"));
+
 #ifdef MALLOC_DEBUG
 	va = NULL;
 	if (malloc_dbg(&va, &size, mtp, flags) != 0)
Index: sys/vm/uma_core.c
===================================================================
--- sys/vm/uma_core.c
+++ sys/vm/uma_core.c
@@ -3328,6 +3328,9 @@
 	uma_cache_bucket_t bucket;
 	uma_cache_t cache;
 
+	KASSERT((flags & M_WAITOK) == 0 || THREAD_CAN_SLEEP(),
+	    ("uma_zalloc_smr(M_WAITOK) in non-sleepable context"));
+
 #ifdef UMA_ZALLOC_DEBUG
 	void *item;
 
@@ -3351,6 +3354,9 @@
 {
 	uma_cache_bucket_t bucket;
 	uma_cache_t cache;
+
+	KASSERT((flags & M_WAITOK) == 0 || THREAD_CAN_SLEEP(),
+	    ("uma_zalloc(M_WAITOK) in non-sleepable context"));
 
 	/* Enable entropy collection for RANDOM_ENABLE_UMA kernel option */
 	random_harvest_fast_uma(&zone, sizeof(zone), RANDOM_UMA);