From a79f0da80a508448434476b77f9d3d1a469eab67 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 3 Jul 2009 16:50:10 +0200 Subject: 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 Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Mike Galbraith Cc: Paul Mackerras Cc: Arnaldo Carvalho de Melo Cc: Frederic Weisbecker Cc: David Howells Cc: Andrew Morton Cc: Arnd Bergmann LKML-Reference: <4A4E1AA2.30002@gmail.com> [ Also fix typo in atomic64_set() export ] Signed-off-by: Ingo Molnar --- arch/x86/include/asm/atomic_32.h | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) (limited to 'arch/x86/include') diff --git a/arch/x86/include/asm/atomic_32.h b/arch/x86/include/asm/atomic_32.h index d7c8849b8c67..dc5a667ff791 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); /** -- cgit v1.2.3