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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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