linux-kernel - generic swap()

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Date:	Fri, 16 Jan 2009 10:26:34 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Wu Fengguang <wfg@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	L-K <linux-kernel@...r.kernel.org>
Subject: generic swap()

Hi,

Where did this patch come from? -- I can't seem to find it on lkml at all..

The reason I ask it that I wonder why swap() has a return value?

---

commit 91f68b7359144aa40bb9668124543d15284750b4
Author: Wu Fengguang <fengguang.wu@...el.com>
Date:   Wed Jan 7 18:09:12 2009 -0800

    generic swap(): introduce global macro swap(a, b)
    
    There have been some local definitions of swap(), it's time to replace
    them all with a uniform one.
    
    Signed-off-by: Wu Fengguang <fengguang.wu@...el.com>
    Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 6b8e202..343df9e 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -476,6 +476,12 @@ static inline char *pack_hex_byte(char *buf, u8 byte)
 	__val = __val < __min ? __min: __val;	\
 	__val > __max ? __max: __val; })
 
+
+/*
+ * swap - swap value of @a and @b
+ */
+#define swap(a, b) ({ typeof(a) __tmp = (a); (a) = (b); (b) = __tmp; })
+
 /**
  * container_of - cast a member of a structure out to the containing structure
  * @ptr:	the pointer to the member.


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