Index: sys/kern/subr_hash.c
===================================================================
--- sys/kern/subr_hash.c
+++ sys/kern/subr_hash.c
@@ -104,16 +104,21 @@
 #define NPRIMES (sizeof(primes) / sizeof(primes[0]))
 
 /*
- * General routine to allocate a prime number sized hash table.
+ * General routine to allocate a prime number sized hash table with control of
+ * memory flags.
  */
 void *
-phashinit(int elements, struct malloc_type *type, u_long *nentries)
+phashinit_flags(int elements, struct malloc_type *type, u_long *nentries, int flags)
 {
 	long hashsize;
 	LIST_HEAD(generic, generic) *hashtbl;
-	int i;
+	int i, m_flags;
 
 	KASSERT(elements > 0, ("%s: bad elements", __func__));
+	/* Exactly one of HASH_WAITOK and HASH_NOWAIT must be set. */
+	KASSERT((flags & HASH_WAITOK) ^ (flags & HASH_NOWAIT),
+	    ("Bad flags (0x%x) passed to phashinit_flags", flags));
+
 	for (i = 1, hashsize = primes[1]; hashsize <= elements;) {
 		i++;
 		if (i == NPRIMES)
@@ -121,9 +126,28 @@
 		hashsize = primes[i];
 	}
 	hashsize = primes[i - 1];
-	hashtbl = malloc((u_long)hashsize * sizeof(*hashtbl), type, M_WAITOK);
+
+	if (flags & HASH_NOWAIT)
+		m_flags = M_NOWAIT;
+	else
+		m_flags = M_WAITOK;
+	hashtbl = malloc((u_long)hashsize * sizeof(*hashtbl), type, m_flags);
+	if (hashtbl == NULL)
+		return (NULL);
+
 	for (i = 0; i < hashsize; i++)
 		LIST_INIT(&hashtbl[i]);
 	*nentries = hashsize;
 	return (hashtbl);
 }
+
+/*
+ * Allocate and initialize a prime number sized hash table with default flag:
+ * may sleep.
+ */
+void *
+phashinit(int elements, struct malloc_type *type, u_long *nentries)
+{
+
+	return (phashinit_flags(elements, type, nentries, HASH_WAITOK));
+}
Index: sys/sys/systm.h
===================================================================
--- sys/sys/systm.h
+++ sys/sys/systm.h
@@ -189,6 +189,8 @@
 #define	HASH_WAITOK	0x00000002
 
 void	*phashinit(int count, struct malloc_type *type, u_long *nentries);
+void	*phashinit_flags(int count, struct malloc_type *type, u_long *nentries,
+    int flags /* HASH_{NOWAIT,WAITOK} */);
 void	g_waitidle(void);
 
 void	panic(const char *, ...) __dead2 __printflike(1, 2);