| Message ID | 20160829171701.14025-1-bobby.prani@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 29/08/2016 19:17, Pranith Kumar wrote: > 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: Pranith Kumar <bobby.prani@gmail.com> > --- > include/qemu/atomic.h | 24 ++++++++---------------- > 1 file changed, 8 insertions(+), 16 deletions(-) > > v2: > - convert atomic_load() and atomic_compare_exchange() > > diff --git a/include/qemu/atomic.h b/include/qemu/atomic.h > index 43b0645..9bb991e 100644 > --- a/include/qemu/atomic.h > +++ b/include/qemu/atomic.h > @@ -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; \ > }) > Thanks, looks good. Paolo
On 08/29/2016 10:17 AM, Pranith Kumar wrote: > #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); \ Technically this produces a different type result. E.g. an int instead of an enum. I don't know if we have any such uses... r~
diff --git a/include/qemu/atomic.h b/include/qemu/atomic.h index 43b0645..9bb991e 100644 --- a/include/qemu/atomic.h +++ b/include/qemu/atomic.h @@ -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; \ })
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: Pranith Kumar <bobby.prani@gmail.com> --- include/qemu/atomic.h | 24 ++++++++---------------- 1 file changed, 8 insertions(+), 16 deletions(-) v2: - convert atomic_load() and atomic_compare_exchange()