The patch titled
Subject: mm/page_alloc: prevent concurrent updaters of pcp ->batch and ->high
has been added to the -mm tree. Its filename is
mm-page_alloc-prevent-concurrent-updaters-of-pcp-batch-and-high.patch
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------------------------------------------------------
From: Cody P Schafer <cody@xxxxxxxxxxxxxxxxxx>
Subject: mm/page_alloc: prevent concurrent updaters of pcp ->batch and ->high
Because we are going to rely upon a careful transision between old and new
->high and ->batch values using memory barriers and will remove
stop_machine(), we need to prevent multiple updaters from interweaving
their memory writes.
Add a simple mutex to protect both update loops.
Signed-off-by: Cody P Schafer <cody@xxxxxxxxxxxxxxxxxx>
Cc: Gilad Ben-Yossef <gilad@xxxxxxxxxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff -puN mm/page_alloc.c~mm-page_alloc-prevent-concurrent-updaters-of-pcp-batch-and-high mm/page_alloc.c
--- a/mm/page_alloc.c~mm-page_alloc-prevent-concurrent-updaters-of-pcp-batch-and-high
+++ a/mm/page_alloc.c
@@ -65,6 +65,9 @@
#include <asm/div64.h>
#include "internal.h"
+/* prevent >1 _updater_ of zone percpu pageset ->high and ->batch fields */
+static DEFINE_MUTEX(pcp_batch_high_lock);
+
#ifdef CONFIG_USE_PERCPU_NUMA_NODE_ID
DEFINE_PER_CPU(int, numa_node);
EXPORT_PER_CPU_SYMBOL(numa_node);
@@ -5557,6 +5560,8 @@ int percpu_pagelist_fraction_sysctl_hand
ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
if (!write || (ret < 0))
return ret;
+
+ mutex_lock(&pcp_batch_high_lock);
for_each_populated_zone(zone) {
for_each_possible_cpu(cpu) {
unsigned long high;
@@ -5565,6 +5570,7 @@ int percpu_pagelist_fraction_sysctl_hand
per_cpu_ptr(zone->pageset, cpu), high);
}
}
+ mutex_unlock(&pcp_batch_high_lock);
return 0;
}
@@ -6078,7 +6084,9 @@ static int __meminit __zone_pcp_update(v
void __meminit zone_pcp_update(struct zone *zone)
{
+ mutex_lock(&pcp_batch_high_lock);
stop_machine(__zone_pcp_update, zone, NULL);
+ mutex_unlock(&pcp_batch_high_lock);
}
#endif
_
Patches currently in -mm which might be from cody@xxxxxxxxxxxxxxxxxx are
mm-page_alloc-factor-out-setting-of-pcp-high-and-pcp-batch.patch
mm-page_alloc-prevent-concurrent-updaters-of-pcp-batch-and-high.patch
mm-page_alloc-insert-memory-barriers-to-allow-async-update-of-pcp-batch-and-high.patch
mm-page_alloc-protect-pcp-batch-accesses-with-access_once.patch
mm-page_alloc-convert-zone_pcp_update-to-rely-on-memory-barriers-instead-of-stop_machine.patch
mm-page_alloc-when-handling-percpu_pagelist_fraction-dont-unneedly-recalulate-high.patch
mm-page_alloc-factor-setup_pageset-into-pageset_init-and-pageset_set_batch.patch
mm-page_alloc-relocate-comment-to-be-directly-above-code-it-refers-to.patch
mm-page_alloc-factor-zone_pageset_init-out-of-setup_zone_pageset.patch
mm-page_alloc-in-zone_pcp_update-uze-zone_pageset_init.patch
mm-page_alloc-rename-setup_pagelist_highmark-to-match-naming-of-pageset_set_batch.patch
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