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>
[ Also fix typo in atomic64_set() export ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/arch/x86/include/asm/atomic_32.h b/arch/x86/include/asm/atomic_32.h
index d7c8849..dc5a667 100644 (file)
--- 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 (file)
--- 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