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>
---
mm/page_alloc.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 9e556e6..cea883d 100644
--- a/mm/page_alloc.c
+++ b/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);
@@ -5555,6 +5558,8 @@ 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;
@@ -5563,6 +5568,7 @@ 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;
}
@@ -6076,7 +6082,9 @@ 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
--
1.8.2.2
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