Module Name: src
Committed By: riastradh
Date: Sat Oct 28 17:06:43 UTC 2017
Modified Files:
src/sys/kern: subr_pool.c
Log Message:
Allow only one pending call to a pool's backing allocator at a time.
Candidate fix for problems with hanging after kva fragmentation related
to PR kern/45718.
Proposed on tech-kern:
https://mail-index.NetBSD.org/tech-kern/2017/10/23/msg022472.html
Tested by bouyer@ on i386.
This makes one small change to the semantics of pool_prime and
pool_setlowat: they may fail with EWOULDBLOCK instead of ENOMEM, if
there is a pending call to the backing allocator in another thread but
we are not actually out of memory. That is unlikely because nearly
always these are used during initialization, when the pool is not in
use.
XXX pullup-8
XXX pullup-7
XXX pullup-6 (requires tweaking the patch)
XXX pullup-5...
To generate a diff of this commit:
cvs rdiff -u -r1.208 -r1.209 src/sys/kern/subr_pool.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/kern/subr_pool.c
diff -u src/sys/kern/subr_pool.c:1.208 src/sys/kern/subr_pool.c:1.209
--- src/sys/kern/subr_pool.c:1.208 Thu Jun 8 04:00:01 2017
+++ src/sys/kern/subr_pool.c Sat Oct 28 17:06:43 2017
@@ -1,4 +1,4 @@
-/* $NetBSD: subr_pool.c,v 1.208 2017/06/08 04:00:01 chs Exp $ */
+/* $NetBSD: subr_pool.c,v 1.209 2017/10/28 17:06:43 riastradh 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 1.208 2017/06/08 04:00:01 chs Exp $");
+__KERNEL_RCSID(0, "$NetBSD: subr_pool.c,v 1.209 2017/10/28 17:06:43 riastradh Exp $");
#ifdef _KERNEL_OPT
#include "opt_ddb.h"
@@ -1051,6 +1051,23 @@ 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.
+ */
+ if (pp->pr_flags & PR_GROWING) {
+ if (flags & PR_WAITOK) {
+ do {
+ cv_wait(&pp->pr_cv, &pp->pr_lock);
+ } while (pp->pr_flags & PR_GROWING);
+ return ERESTART;
+ } else {
+ return EWOULDBLOCK;
+ }
+ }
+ pp->pr_flags |= PR_GROWING;
mutex_exit(&pp->pr_lock);
cp = pool_allocator_alloc(pp, flags);
@@ -1062,13 +1079,25 @@ pool_grow(struct pool *pp, int flags)
pool_allocator_free(pp, cp);
}
mutex_enter(&pp->pr_lock);
- return ENOMEM;
+ error = ENOMEM;
+ goto out;
}
mutex_enter(&pp->pr_lock);
pool_prime_page(pp, cp, ph);
pp->pr_npagealloc++;
- return 0;
+ error = 0;
+
+out:
+ /*
+ * If anyone was waiting for pool_grow, notify them that we
+ * may have just done it.
+ */
+ KASSERT(pp->pr_flags & PR_GROWING);
+ pp->pr_flags &= ~PR_GROWING;
+ cv_broadcast(&pp->pr_cv);
+
+ return error;
}
/*
