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Commit c8e251fa authored by Cody P Schafer's avatar Cody P Schafer Committed by Linus Torvalds
Browse files

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: default avatarCody 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4008bab7

mm/page_alloc.c

+8 −0
Original line number Diff line number Diff line
@@ -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_handler(ctl_table *table, int write, 
	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_handler(ctl_table *table, int write, 
				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(void *data) 


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