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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@linux.vnet.ibm.com>
Cc: Gilad Ben-Yossef <gilad@benyossef.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Cody P Schafer 2013-07-03 15:01:29 -07:00 committed by Linus Torvalds
parent 4008bab7b3
commit c8e251fadc
1 changed files with 8 additions and 0 deletions
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8
mm/page_alloc.c
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@ -65,6 +65,9 @@
#include <asm/div64.h> #include <asm/div64.h>
#include "internal.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 #ifdef CONFIG_USE_PERCPU_NUMA_NODE_ID
DEFINE_PER_CPU(int, numa_node); DEFINE_PER_CPU(int, numa_node);
EXPORT_PER_CPU_SYMBOL(numa_node); EXPORT_PER_CPU_SYMBOL(numa_node);
@ -5557,6 +5560,8 @@ int percpu_pagelist_fraction_sysctl_handler(ctl_table *table, int write,
ret = proc_dointvec_minmax(table, write, buffer, length, ppos); ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
if (!write || (ret < 0)) if (!write || (ret < 0))
return ret; return ret;
mutex_lock(&pcp_batch_high_lock);
for_each_populated_zone(zone) { for_each_populated_zone(zone) {
for_each_possible_cpu(cpu) { for_each_possible_cpu(cpu) {
unsigned long high; unsigned long high;
@ -5565,6 +5570,7 @@ int percpu_pagelist_fraction_sysctl_handler(ctl_table *table, int write,
per_cpu_ptr(zone->pageset, cpu), high); per_cpu_ptr(zone->pageset, cpu), high);
} }
} }
mutex_unlock(&pcp_batch_high_lock);
return 0; return 0;
} }
@ -6078,7 +6084,9 @@ static int __meminit __zone_pcp_update(void *data)
void __meminit zone_pcp_update(struct zone *zone) void __meminit zone_pcp_update(struct zone *zone)
{ {
mutex_lock(&pcp_batch_high_lock);
stop_machine(__zone_pcp_update, zone, NULL); stop_machine(__zone_pcp_update, zone, NULL);
mutex_unlock(&pcp_batch_high_lock);
} }
#endif #endif