linux-kernel - [PATCH v2 03/10] mm/page_alloc: insert memory barriers to allow async update of pcp batch and high

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1365550099-6795-4-git-send-email-cody@linux.vnet.ibm.com>
Date:	Tue,  9 Apr 2013 16:28:12 -0700
From:	Cody P Schafer <cody@...ux.vnet.ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Gilad Ben-Yossef <gilad@...yossef.com>,
	Simon Jeons <simon.jeons@...il.com>,
	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	Mel Gorman <mgorman@...e.de>, Linux MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Cody P Schafer <cody@...ux.vnet.ibm.com>
Subject: [PATCH v2 03/10] mm/page_alloc: insert memory barriers to allow async update of pcp batch and high

In pageset_set_batch() and setup_pagelist_highmark(), ensure that batch
is always set to a safe value (1) prior to updating high, and ensure
that high is fully updated before setting the real value of batch.

Suggested by Gilad Ben-Yossef <gilad@...yossef.com> in this thread:

	https://lkml.org/lkml/2013/4/9/23

Also reproduces his proposed comment.

Signed-off-by: Cody P Schafer <cody@...ux.vnet.ibm.com>
---
 mm/page_alloc.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index d259599..a07bd4c 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4007,11 +4007,26 @@ static int __meminit zone_batchsize(struct zone *zone)
 #endif
 }
 
+static void pageset_update_prep(struct per_cpu_pages *pcp)
+{
+	/*
+	 * We're about to mess with PCP in an non atomic fashion.  Put an
+	 * intermediate safe value of batch and make sure it is visible before
+	 * any other change
+	 */
+	pcp->batch = 1;
+	smp_wmb();
+}
+
 /* a companion to setup_pagelist_highmark() */
 static void pageset_set_batch(struct per_cpu_pageset *p, unsigned long batch)
 {
 	struct per_cpu_pages *pcp = &p->pcp;
+	pageset_update_prep(pcp);
+
 	pcp->high = 6 * batch;
+	smp_wmb();
+
 	pcp->batch = max(1UL, 1 * batch);
 }
 
@@ -4039,7 +4054,11 @@ static void setup_pagelist_highmark(struct per_cpu_pageset *p,
 	struct per_cpu_pages *pcp;
 
 	pcp = &p->pcp;
+	pageset_update_prep(pcp);
+
 	pcp->high = high;
+	smp_wmb();
+
 	pcp->batch = max(1UL, high/4);
 	if ((high/4) > (PAGE_SHIFT * 8))
 		pcp->batch = PAGE_SHIFT * 8;
-- 
1.8.2

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/