From c8e251fadc6220261f6e0c6b8a4f1cdf27626165 Mon Sep 17 00:00:00 2001 From: Cody P Schafer Date: Wed, 3 Jul 2013 15:01:29 -0700 Subject: [PATCH] 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 Cc: Gilad Ben-Yossef Cc: KOSAKI Motohiro Cc: Mel Gorman Cc: Pekka Enberg Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/page_alloc.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index d4bcc20ab6f0..8d4335779633 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -65,6 +65,9 @@ #include #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 -- 2.20.1