[PATCH 04/29] mm: serialize access to min_free_kbytes

From: Peter Zijlstra
Date: Wed Feb 21 2007 - 10:34:05 EST


There is a small race between the procfs caller and the memory hotplug caller
of setup_per_zone_pages_min(). Not a big deal, but the next patch will add yet
another caller. Time to close the gap.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
---
mm/page_alloc.c | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)

Index: linux-2.6-git/mm/page_alloc.c
===================================================================
--- linux-2.6-git.orig/mm/page_alloc.c 2007-01-15 09:58:49.000000000 +0100
+++ linux-2.6-git/mm/page_alloc.c 2007-01-15 09:58:51.000000000 +0100
@@ -95,6 +95,7 @@ static char * const zone_names[MAX_NR_ZO
#endif
};

+static DEFINE_SPINLOCK(min_free_lock);
int min_free_kbytes = 1024;

unsigned long __meminitdata nr_kernel_pages;
@@ -3074,12 +3075,12 @@ static void setup_per_zone_lowmem_reserv
}

/**
- * setup_per_zone_pages_min - called when min_free_kbytes changes.
+ * __setup_per_zone_pages_min - called when min_free_kbytes changes.
*
* Ensures that the pages_{min,low,high} values for each zone are set correctly
* with respect to min_free_kbytes.
*/
-void setup_per_zone_pages_min(void)
+static void __setup_per_zone_pages_min(void)
{
unsigned long pages_min = min_free_kbytes >> (PAGE_SHIFT - 10);
unsigned long lowmem_pages = 0;
@@ -3133,6 +3134,15 @@ void setup_per_zone_pages_min(void)
calculate_totalreserve_pages();
}

+void setup_per_zone_pages_min(void)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&min_free_lock, flags);
+ __setup_per_zone_pages_min();
+ spin_unlock_irqrestore(&min_free_lock, flags);
+}
+
/*
* Initialise min_free_kbytes.
*
@@ -3168,7 +3178,7 @@ static int __init init_per_zone_pages_mi
min_free_kbytes = 128;
if (min_free_kbytes > 65536)
min_free_kbytes = 65536;
- setup_per_zone_pages_min();
+ __setup_per_zone_pages_min();
setup_per_zone_lowmem_reserve();
return 0;
}

--

-
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