linux-kernel - [tip:perfcounters/urgent] x86: atomic64: Inline atomic64

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Message-ID: <tip-a79f0da80a508448434476b77f9d3d1a469eab67@git.kernel.org>
Date:	Sat, 4 Jul 2009 09:49:03 GMT
From:	tip-bot for Eric Dumazet <eric.dumazet@...il.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, acme@...hat.com, paulus@...ba.org,
	hpa@...or.com, mingo@...hat.com, eric.dumazet@...il.com,
	a.p.zijlstra@...llo.nl, torvalds@...ux-foundation.org,
	efault@....de, arnd@...db.de, dhowells@...hat.com,
	fweisbec@...il.com, akpm@...ux-foundation.org, tglx@...utronix.de,
	mingo@...e.hu
Subject: [tip:perfcounters/urgent] x86: atomic64: Inline atomic64_read() again

Commit-ID:  a79f0da80a508448434476b77f9d3d1a469eab67
Gitweb:     http://git.kernel.org/tip/a79f0da80a508448434476b77f9d3d1a469eab67
Author:     Eric Dumazet <eric.dumazet@...il.com>
AuthorDate: Fri, 3 Jul 2009 16:50:10 +0200
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Sat, 4 Jul 2009 11:45:00 +0200

x86: atomic64: Inline atomic64_read() again

Now atomic64_read() is light weight (no register pressure and
small icache), we can inline it again.

Also use "=&A" constraint instead of "+A" to avoid warning
about unitialized 'res' variable. (gcc had to force 0 in eax/edx)

  $ size vmlinux.prev vmlinux.after
     text    data     bss     dec     hex filename
  4908667  451676 1684868 7045211  6b805b vmlinux.prev
  4908651  451676 1684868 7045195  6b804b vmlinux.after

Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Mike Galbraith <efault@....de>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: David Howells <dhowells@...hat.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Arnd Bergmann <arnd@...db.de>
LKML-Reference: <4A4E1AA2.30002@...il.com>
[ Also fix typo in atomic64_set() export ]
Signed-off-by: Ingo Molnar <mingo@...e.hu>


---
 arch/x86/include/asm/atomic_32.h |   22 ++++++++++++++++++++++
 arch/x86/lib/atomic64_32.c       |   23 +----------------------
 2 files changed, 23 insertions(+), 22 deletions(-)

diff --git a/arch/x86/include/asm/atomic_32.h b/arch/x86/include/asm/atomic_32.h
index d7c8849..dc5a667 100644
--- a/arch/x86/include/asm/atomic_32.h
+++ b/arch/x86/include/asm/atomic_32.h
@@ -295,6 +295,28 @@ extern void atomic64_set(atomic64_t *ptr, u64 new_val);
  *
  * Atomically reads the value of @ptr and returns it.
  */
+static inline u64 atomic64_read(atomic64_t *ptr)
+{
+	u64 res;
+
+	/*
+	 * Note, we inline this atomic64_t primitive because
+	 * it only clobbers EAX/EDX and leaves the others
+	 * untouched. We also (somewhat subtly) rely on the
+	 * fact that cmpxchg8b returns the current 64-bit value
+	 * of the memory location we are touching:
+	 */
+	asm volatile(
+		"mov %%ebx, %%eax\n\t"
+		"mov %%ecx, %%edx\n\t"
+		LOCK_PREFIX "cmpxchg8b %1\n"
+			: "=&A" (res)
+			: "m" (*ptr)
+		);
+
+	return res;
+}
+
 extern u64 atomic64_read(atomic64_t *ptr);
 
 /**
diff --git a/arch/x86/lib/atomic64_32.c b/arch/x86/lib/atomic64_32.c
index 1d98c9e..824fa0b 100644
--- a/arch/x86/lib/atomic64_32.c
+++ b/arch/x86/lib/atomic64_32.c
@@ -66,31 +66,10 @@ void atomic64_set(atomic64_t *ptr, u64 new_val)
 {
 	atomic64_xchg(ptr, new_val);
 }
-EXPORT_SYMBOL(atomic64_read);
+EXPORT_SYMBOL(atomic64_set);
 
 /**
- * atomic64_read - read atomic64 variable
- * @ptr:      pointer to type atomic64_t
- *
- * Atomically reads the value of @ptr and returns it.
- */
-u64 atomic64_read(atomic64_t *ptr)
-{
-	u64 res;
-
-	asm volatile(
-		"mov %%ebx, %%eax\n\t"
-		"mov %%ecx, %%edx\n\t"
-		LOCK_PREFIX "cmpxchg8b %1\n"
-			: "+A" (res)
-			: "m" (*ptr)
-		);
-
-	return res;
-}
 EXPORT_SYMBOL(atomic64_read);
-
-/**
  * atomic64_add_return - add and return
  * @delta: integer value to add
  * @ptr:   pointer to type atomic64_t
--
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