Commit 89943de1 authored by Pranith Kumar's avatar Pranith Kumar Committed by Paolo Bonzini
Browse files

atomics: Use __atomic_*_n() variant primitives 



Use the __atomic_*_n() primitives which take the value as argument. It
is not necessary to store the value locally before calling the
primitive, hence saving us a stack store and load.

Signed-off-by: default avatarPranith Kumar <bobby.prani@gmail.com>
Message-Id: <20160829171701.14025-1-bobby.prani@gmail.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 705ac1ca

include/qemu/atomic.h

+8 −16
Original line number Diff line number Diff line
@@ -96,15 +96,12 @@ 
#define atomic_read(ptr)                              \

    ({                                                \

    QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \

    typeof_strip_qual(*ptr) _val;                     \

     __atomic_load(ptr, &_val, __ATOMIC_RELAXED);     \

    _val;                                             \

    __atomic_load_n(ptr, __ATOMIC_RELAXED);           \

    })



#define atomic_set(ptr, i)  do {                      \

    QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \

    typeof(*ptr) _val = (i);                          \

    __atomic_store(ptr, &_val, __ATOMIC_RELAXED);     \

    __atomic_store_n(ptr, i, __ATOMIC_RELAXED);       \

} while(0)



/* See above: most compilers currently treat consume and acquire the
@@ -129,8 +126,7 @@ 


#define atomic_rcu_set(ptr, i) do {                   \

    QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \

    typeof(*ptr) _val = (i);                          \

    __atomic_store(ptr, &_val, __ATOMIC_RELEASE);     \

    __atomic_store_n(ptr, i, __ATOMIC_RELEASE);       \

} while(0)



/* atomic_mb_read/set semantics map Java volatile variables. They are
@@ -153,9 +149,8 @@ 


#define atomic_mb_set(ptr, i)  do {                     \

    QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *));   \

    typeof(*ptr) _val = (i);                            \

    smp_wmb();                                          \

    __atomic_store(ptr, &_val, __ATOMIC_RELAXED);       \

    __atomic_store_n(ptr, i, __ATOMIC_RELAXED);         \

    smp_mb();                                           \

} while(0)

#else
@@ -169,8 +164,7 @@ 


#define atomic_mb_set(ptr, i)  do {                     \

    QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *));   \

    typeof(*ptr) _val = (i);                            \

    __atomic_store(ptr, &_val, __ATOMIC_SEQ_CST);       \

    __atomic_store_n(ptr, i, __ATOMIC_SEQ_CST);         \

} while(0)

#endif
@@ -179,17 +173,15 @@ 


#define atomic_xchg(ptr, i)    ({                           \

    QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *));       \

    typeof_strip_qual(*ptr) _new = (i), _old;               \

    __atomic_exchange(ptr, &_new, &_old, __ATOMIC_SEQ_CST); \

    _old;                                                   \

    __atomic_exchange_n(ptr, i, __ATOMIC_SEQ_CST);          \

})



/* Returns the eventual value, failed or not */

#define atomic_cmpxchg(ptr, old, new)                                   \

    ({                                                                  \

    QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *));                   \

    typeof_strip_qual(*ptr) _old = (old), _new = (new);                 \

    __atomic_compare_exchange(ptr, &_old, &_new, false,                 \

    typeof_strip_qual(*ptr) _old = (old);                               \

    __atomic_compare_exchange_n(ptr, &_old, new, false,                 \

                              __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);      \

    _old;                                                               \

    })