linux-kernel - [PATCH 1/4]percpu_counter: make API return consistent value

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Message-ID: <1302595437.3981.127.camel@sli10-conroe>
Date:	Tue, 12 Apr 2011 16:03:57 +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 1/4]percpu_counter: make API return consistent value

the percpu_counter_*_positive() API SMP and !SMP aren't consistent. From
the API name, we should return a non-negative value for them.
Also if count < 0, returns 0 instead of 1 for *read_positive().

Signed-off-by: Shaohua Li <shaohua.li@...el.com>

---
 include/linux/percpu_counter.h |   52 ++++++++++++++++-------------------------
 1 file changed, 21 insertions(+), 31 deletions(-)

Index: linux/include/linux/percpu_counter.h
===================================================================
--- linux.orig/include/linux/percpu_counter.h	2011-04-12 15:48:42.000000000 +0800
+++ linux/include/linux/percpu_counter.h	2011-04-12 15:48:44.000000000 +0800
@@ -47,12 +47,6 @@ static inline void percpu_counter_add(st
 	__percpu_counter_add(fbc, amount, percpu_counter_batch);
 }
 
-static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
-{
-	s64 ret = __percpu_counter_sum(fbc);
-	return ret < 0 ? 0 : ret;
-}
-
 static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
 {
 	return __percpu_counter_sum(fbc);
@@ -63,21 +57,6 @@ static inline s64 percpu_counter_read(st
 	return fbc->count;
 }
 
-/*
- * It is possible for the percpu_counter_read() to return a small negative
- * number for some counter which should never be negative.
- *
- */
-static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
-{
-	s64 ret = fbc->count;
-
-	barrier();		/* Prevent reloads of fbc->count */
-	if (ret >= 0)
-		return ret;
-	return 1;
-}
-
 static inline int percpu_counter_initialized(struct percpu_counter *fbc)
 {
 	return (fbc->counters != NULL);
@@ -133,16 +112,6 @@ static inline s64 percpu_counter_read(st
 	return fbc->count;
 }
 
-static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
-{
-	return fbc->count;
-}
-
-static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
-{
-	return percpu_counter_read_positive(fbc);
-}
-
 static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
 {
 	return percpu_counter_read(fbc);
@@ -170,4 +139,25 @@ static inline void percpu_counter_sub(st
 	percpu_counter_add(fbc, -amount);
 }
 
+/*
+ * It is possible for the percpu_counter_read() to return a small negative
+ * number for some counter which should never be negative.
+ *
+ */
+static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
+{
+	s64 ret = percpu_counter_read(fbc);
+
+	barrier();		/* Prevent reloads of fbc->count */
+	if (ret >= 0)
+		return ret;
+	return 0;
+}
+
+static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
+{
+	s64 ret = percpu_counter_sum(fbc);
+	return ret < 0 ? 0 : ret;
+}
+
 #endif /* _LINUX_PERCPU_COUNTER_H */


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