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Message-ID: <1302595444.3981.129.camel@sli10-conroe>
Date: Tue, 12 Apr 2011 16:04:04 +0800
From: Shaohua Li <shaohua.li@...el.com>
To: lkml <linux-kernel@...r.kernel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>, cl@...ux.com,
tj@...nel.org
Subject: [PATCH 3/4]percpu_counter: fix code for 32bit systems
percpu_counter.counter is a 's64'. Accessing it in 32-bit system is racing.
we need some locking to protect it otherwise some very wrong value could be
accessed.
Signed-off-by: Shaohua Li <shaohua.li@...el.com>
---
include/linux/percpu_counter.h | 43 +++++++++++++++++++++++++++++++----------
1 file changed, 33 insertions(+), 10 deletions(-)
Index: linux/include/linux/percpu_counter.h
===================================================================
--- linux.orig/include/linux/percpu_counter.h 2011-04-12 15:48:44.000000000 +0800
+++ linux/include/linux/percpu_counter.h 2011-04-12 15:48:54.000000000 +0800
@@ -54,7 +54,15 @@ static inline s64 percpu_counter_sum(str
static inline s64 percpu_counter_read(struct percpu_counter *fbc)
{
+#if BITS_PER_LONG == 32
+ s64 count;
+ spin_lock(&fbc->lock);
+ count = fbc->count;
+ spin_unlock(&fbc->lock);
+ return count;
+#else
return fbc->count;
+#endif
}
static inline int percpu_counter_initialized(struct percpu_counter *fbc)
@@ -68,9 +76,20 @@ struct percpu_counter {
s64 count;
};
-static inline int percpu_counter_init(struct percpu_counter *fbc, s64 amount)
+static inline void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
{
+#if BITS_PER_LONG == 32
+ preempt_disable();
fbc->count = amount;
+ preempt_enable();
+#else
+ fbc->count = amount;
+#endif
+}
+
+static inline int percpu_counter_init(struct percpu_counter *fbc, s64 amount)
+{
+ percpu_counter_set(fbc, amount);
return 0;
}
@@ -78,16 +97,25 @@ static inline void percpu_counter_destro
{
}
-static inline void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
+static inline s64 percpu_counter_read(struct percpu_counter *fbc)
{
- fbc->count = amount;
+#if BITS_PER_LONG == 32
+ s64 count;
+ preempt_disable();
+ count = fbc->count;
+ preempt_enable();
+ return count;
+#else
+ return fbc->count;
+#endif
}
static inline int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs)
{
- if (fbc->count > rhs)
+ s64 count = percpu_counter_read(fbc);
+ if (count > rhs)
return 1;
- else if (fbc->count < rhs)
+ else if (count < rhs)
return -1;
else
return 0;
@@ -107,11 +135,6 @@ __percpu_counter_add(struct percpu_count
percpu_counter_add(fbc, amount);
}
-static inline s64 percpu_counter_read(struct percpu_counter *fbc)
-{
- return fbc->count;
-}
-
static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
{
return percpu_counter_read(fbc);
--
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