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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>
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1 changed files with 8 additions and 0 deletions
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@ -65,6 +65,9 @@
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#include <asm/div64.h>
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#include "internal.h"
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/* prevent >1 _updater_ of zone percpu pageset ->high and ->batch fields */
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static DEFINE_MUTEX(pcp_batch_high_lock);
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#ifdef CONFIG_USE_PERCPU_NUMA_NODE_ID
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DEFINE_PER_CPU(int, numa_node);
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EXPORT_PER_CPU_SYMBOL(numa_node);
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@ -5557,6 +5560,8 @@ int percpu_pagelist_fraction_sysctl_handler(ctl_table *table, int write,
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ret = proc_dointvec_minmax(table, write, buffer, length, ppos);
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if (!write || (ret < 0))
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return ret;
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mutex_lock(&pcp_batch_high_lock);
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for_each_populated_zone(zone) {
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for_each_possible_cpu(cpu) {
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unsigned long high;
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@ -5565,6 +5570,7 @@ int percpu_pagelist_fraction_sysctl_handler(ctl_table *table, int write,
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per_cpu_ptr(zone->pageset, cpu), high);
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}
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}
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mutex_unlock(&pcp_batch_high_lock);
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return 0;
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}
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@ -6078,7 +6084,9 @@ static int __meminit __zone_pcp_update(void *data)
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void __meminit zone_pcp_update(struct zone *zone)
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{
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mutex_lock(&pcp_batch_high_lock);
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stop_machine(__zone_pcp_update, zone, NULL);
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mutex_unlock(&pcp_batch_high_lock);
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}
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#endif
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