diff options
Diffstat (limited to 'gcc')
| -rw-r--r-- | gcc/ChangeLog | 5 | ||||
| -rw-r--r-- | gcc/doc/extend.texi | 6 |
2 files changed, 9 insertions, 2 deletions
diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 1659094..889cbcc 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,5 +1,10 @@ 2013-06-21 Andi Kleen <ak@linux.intel.com> + * doc/extend.texi: Dont use __atomic_clear in HLE + example. Fix typo. + +2013-06-21 Andi Kleen <ak@linux.intel.com> + * doc/extend.texi: Document that __atomic_clear and __atomic_test_and_set should only be used with bool. diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi index 213cf00..77295f1 100644 --- a/gcc/doc/extend.texi +++ b/gcc/doc/extend.texi @@ -7525,18 +7525,20 @@ End lock elision on a lock variable. Memory model must be @code{__ATOMIC_RELEASE} or stronger. @end table -When a lock acquire fails it's required for good performance to abort +When a lock acquire fails it is required for good performance to abort the transaction quickly. This can be done with a @code{_mm_pause} @smallexample #include <immintrin.h> // For _mm_pause +int lockvar; + /* Acquire lock with lock elision */ while (__atomic_exchange_n(&lockvar, 1, __ATOMIC_ACQUIRE|__ATOMIC_HLE_ACQUIRE)) _mm_pause(); /* Abort failed transaction */ ... /* Free lock with lock elision */ -__atomic_clear(&lockvar, __ATOMIC_RELEASE|__ATOMIC_HLE_RELEASE); +__atomic_store(&lockvar, 0, __ATOMIC_RELEASE|__ATOMIC_HLE_RELEASE); @end smallexample @node Object Size Checking |