[src/trunk]: src/sys/kern - fix an assert; we can reach there if we are nowai...

[christos <christos%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/281933ea2a69
branches:  trunk
changeset: 357542:281933ea2a69
user:      christos <christos%NetBSD.org@localhost>
date:      Tue Nov 14 15:02:06 2017 +0000

description:
- fix an assert; we can reach there if we are nowait or limitfail.
- when priming the pool and failing with ERESTART, don't decrement the number
  of pages; this avoids the issue of returning an ERESTART when we get to 0,
  and is more correct.
- simplify the pool_grow code, and don't wakeup things if we ENOMEM.

diffstat:

 sys/kern/subr_pool.c |  43 +++++++++++++++++++------------------------
 1 files changed, 19 insertions(+), 24 deletions(-)

diffs (104 lines):

diff -r c9924038a49a -r 281933ea2a69 sys/kern/subr_pool.c
--- a/sys/kern/subr_pool.c      Tue Nov 14 14:29:33 2017 +0000
+++ b/sys/kern/subr_pool.c      Tue Nov 14 15:02:06 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: subr_pool.c,v 1.215 2017/11/09 22:52:26 christos Exp $ */
+/*     $NetBSD: subr_pool.c,v 1.216 2017/11/14 15:02:06 christos 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 1.215 2017/11/09 22:52:26 christos Exp $");
+__KERNEL_RCSID(0, "$NetBSD: subr_pool.c,v 1.216 2017/11/14 15:02:06 christos Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_ddb.h"
@@ -809,7 +809,7 @@
                pp->pr_nfail++;
 
                mutex_exit(&pp->pr_lock);
-               KASSERT((flags & (PR_WAITOK|PR_NOWAIT)) == PR_NOWAIT);
+               KASSERT((flags & (PR_NOWAIT|PR_LIMITFAIL)) != 0);
                return (NULL);
        }
 
@@ -1062,10 +1062,6 @@
 static int
 pool_grow(struct pool *pp, int flags)
 {
-       struct pool_item_header *ph = NULL;
-       char *cp;
-       int error;
-
        /*
         * If there's a pool_grow in progress, wait for it to complete
         * and try again from the top.
@@ -1083,34 +1079,32 @@
        pp->pr_flags |= PR_GROWING;
 
        mutex_exit(&pp->pr_lock);
-       cp = pool_allocator_alloc(pp, flags);
-       if (__predict_true(cp != NULL)) {
-               ph = pool_alloc_item_header(pp, cp, flags);
-       }
-       if (__predict_false(cp == NULL || ph == NULL)) {
-               if (cp != NULL) {
-                       pool_allocator_free(pp, cp);
-               }
-               mutex_enter(&pp->pr_lock);
-               error = ENOMEM;
+       char *cp = pool_allocator_alloc(pp, flags);
+       if (__predict_false(cp == NULL))
+               goto out;
+
+       struct pool_item_header *ph = pool_alloc_item_header(pp, cp, flags);
+       if (__predict_false(ph == NULL)) {
+               pool_allocator_free(pp, cp);
                goto out;
        }
 
        mutex_enter(&pp->pr_lock);
        pool_prime_page(pp, cp, ph);
        pp->pr_npagealloc++;
-       error = 0;
-
-out:
+       KASSERT(pp->pr_flags & PR_GROWING);
+       pp->pr_flags &= ~PR_GROWING;
        /*
         * If anyone was waiting for pool_grow, notify them that we
         * may have just done it.
         */
+       cv_broadcast(&pp->pr_cv);
+       return 0;
+out:
        KASSERT(pp->pr_flags & PR_GROWING);
        pp->pr_flags &= ~PR_GROWING;
-       cv_broadcast(&pp->pr_cv);
-
-       return error;
+       mutex_enter(&pp->pr_lock);
+       return ENOMEM;
 }
 
 /*
@@ -1126,7 +1120,7 @@
 
        newpages = roundup(n, pp->pr_itemsperpage) / pp->pr_itemsperpage;
 
-       while (newpages-- > 0) {
+       while (newpages > 0) {
                error = pool_grow(pp, PR_NOWAIT);
                if (error) {
                        if (error == ERESTART)
@@ -1134,6 +1128,7 @@
                        break;
                }
                pp->pr_minpages++;
+               newpages--;
        }
 
        if (pp->pr_minpages >= pp->pr_maxpages)