Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.

===================================================================
RCS file: /ftp/cvs/cvsroot/src/sys/kern/subr_pool.c,v
rcsdiff: /ftp/cvs/cvsroot/src/sys/kern/subr_pool.c,v: warning: Unknown phrases like `commitid ...;' are present.
retrieving revision 1.218
retrieving revision 1.219
diff -u -p -r1.218 -r1.219
--- src/sys/kern/subr_pool.c	2017/12/04 03:05:24	1.218
+++ src/sys/kern/subr_pool.c	2017/12/16 03:13:29	1.219
@@ -1,4 +1,4 @@
-/*	$NetBSD: subr_pool.c,v 1.218 2017/12/04 03:05:24 mrg Exp $	*/
+/*	$NetBSD: subr_pool.c,v 1.219 2017/12/16 03:13:29 mrg Exp $	*/
 
 /*-
  * Copyright (c) 1997, 1999, 2000, 2002, 2007, 2008, 2010, 2014, 2015
@@ -33,7 +33,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: subr_pool.c,v 1.218 2017/12/04 03:05:24 mrg Exp $");
+__KERNEL_RCSID(0, "$NetBSD: subr_pool.c,v 1.219 2017/12/16 03:13:29 mrg Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_ddb.h"
@@ -1073,10 +1073,23 @@ pool_grow(struct pool *pp, int flags)
 			} while (pp->pr_flags & PR_GROWING);
 			return ERESTART;
 		} else {
+			if (pp->pr_flags & PR_GROWINGNOWAIT) {
+				/*
+				 * This needs an unlock/relock dance so
+				 * that the other caller has a chance to
+				 * run and actually do the thing.  Note
+				 * that this is effectively a busy-wait.
+				 */
+				mutex_exit(&pp->pr_lock);
+				mutex_enter(&pp->pr_lock);
+				return ERESTART;
+			}
 			return EWOULDBLOCK;
 		}
 	}
 	pp->pr_flags |= PR_GROWING;
+	if ((flags & PR_WAITOK) == 0)
+		pp->pr_flags |= PR_GROWINGNOWAIT;
 
 	mutex_exit(&pp->pr_lock);
 	char *cp = pool_allocator_alloc(pp, flags);
@@ -1093,7 +1106,7 @@ pool_grow(struct pool *pp, int flags)
 	pool_prime_page(pp, cp, ph);
 	pp->pr_npagealloc++;
 	KASSERT(pp->pr_flags & PR_GROWING);
-	pp->pr_flags &= ~PR_GROWING;
+	pp->pr_flags &= ~(PR_GROWING|PR_GROWINGNOWAIT);
 	/*
 	 * If anyone was waiting for pool_grow, notify them that we
 	 * may have just done it.
@@ -1102,7 +1115,7 @@ pool_grow(struct pool *pp, int flags)
 	return 0;
 out:
 	KASSERT(pp->pr_flags & PR_GROWING);
-	pp->pr_flags &= ~PR_GROWING;
+	pp->pr_flags &= ~(PR_GROWING|PR_GROWINGNOWAIT);
 	mutex_enter(&pp->pr_lock);
 	return ENOMEM;
 }