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Subject[tip:perfcounters/urgent] x86: atomic64: Inline atomic64_read() again
Commit-ID:  5fc6406e15d35b99cd19ec5f1da5b3cc326db2e3
Gitweb: http://git.kernel.org/tip/5fc6406e15d35b99cd19ec5f1da5b3cc326db2e3
Author: Eric Dumazet <eric.dumazet@gmail.com>
AuthorDate: Fri, 3 Jul 2009 16:50:10 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Fri, 3 Jul 2009 21:16:48 +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@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
LKML-Reference: <4A4E1AA2.30002@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
arch/x86/include/asm/atomic_32.h | 22 ++++++++++++++++++++++
arch/x86/lib/atomic64_32.c | 21 ---------------------
2 files changed, 22 insertions(+), 21 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..d79f4ac 100644
--- a/arch/x86/lib/atomic64_32.c
+++ b/arch/x86/lib/atomic64_32.c
@@ -69,28 +69,7 @@ void atomic64_set(atomic64_t *ptr, u64 new_val)
EXPORT_SYMBOL(atomic64_read);

/**
- * 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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