diff options
| -rw-r--r-- | libcxx/www/atomic_design.html | 34 | ||||
| -rw-r--r-- | libcxx/www/atomic_design_a.html | 3 | ||||
| -rw-r--r-- | libcxx/www/atomic_design_b.html | 13 |
3 files changed, 45 insertions, 5 deletions
diff --git a/libcxx/www/atomic_design.html b/libcxx/www/atomic_design.html index 36e73244d91..87a2f624914 100644 --- a/libcxx/www/atomic_design.html +++ b/libcxx/www/atomic_design.html @@ -53,6 +53,40 @@ should be identical (and conforming) for all three designs. </li> </ol> +<p> +With any design, the (back end) compiler writer should note: +</p> + +<blockquote> +<p> +The decision to implement lock-free operations on any given type (or not) is an +ABI-binding decision. One can not change from treating a type as not lock free, +to lock free (or vice-versa) without breaking your ABI. +</p> + +<p> +Example: +</p> + +<blockquote><pre> +TU1.cc +----------- +extern atomic<long long> A; +int foo() { return A.compare_exchange_strong(w, x); } + +TU2.cc +----------- +extern atomic<long long> A; +void bar() { return A.compare_exchange_strong(y, z); } +</pre></blockquote> +</blockquote> + +<p> +If only <em>one</em> of these calls to <tt>compare_exchange_strong</tt> is +implemented with mutex-locked code, then that mutex-locked code will not be +executed mutually exclusively of the one implemented in a lock-free manner. +</p> + </div> </body> </html> diff --git a/libcxx/www/atomic_design_a.html b/libcxx/www/atomic_design_a.html index f09d0b36a53..bcb26271279 100644 --- a/libcxx/www/atomic_design_a.html +++ b/libcxx/www/atomic_design_a.html @@ -50,6 +50,9 @@ the memory ordering parameter. <font color="#C80000">// volatile-qualifed type.</font> <font color="#C80000">// type must be trivially copyable</font> +bool __atomic_is_lock_free(const type* atomic_obj); + +<font color="#C80000">// type must be trivially copyable</font> <font color="#C80000">// Behavior is defined for mem_ord = 0, 1, 2, 5</font> type __atomic_load(const type* atomic_obj, int mem_ord); diff --git a/libcxx/www/atomic_design_b.html b/libcxx/www/atomic_design_b.html index 7891050c132..b738445be36 100644 --- a/libcxx/www/atomic_design_b.html +++ b/libcxx/www/atomic_design_b.html @@ -44,18 +44,21 @@ option in the spirit of completeness. </p> <blockquote><pre> -<font color="#C80000">// type can be any pod</font> +<font color="#C80000">// type must be trivially copyable</font> +bool __atomic_is_lock_free(const type* atomic_obj); + +<font color="#C80000">// type must be trivially copyable</font> type __atomic_load_relaxed(const volatile type* atomic_obj); type __atomic_load_consume(const volatile type* atomic_obj); type __atomic_load_acquire(const volatile type* atomic_obj); type __atomic_load_seq_cst(const volatile type* atomic_obj); -<font color="#C80000">// type can be any pod</font> +<font color="#C80000">// type must be trivially copyable</font> type __atomic_store_relaxed(volatile type* atomic_obj, type desired); type __atomic_store_release(volatile type* atomic_obj, type desired); type __atomic_store_seq_cst(volatile type* atomic_obj, type desired); -<font color="#C80000">// type can be any pod</font> +<font color="#C80000">// type must be trivially copyable</font> type __atomic_exchange_relaxed(volatile type* atomic_obj, type desired); type __atomic_exchange_consume(volatile type* atomic_obj, type desired); type __atomic_exchange_acquire(volatile type* atomic_obj, type desired); @@ -63,7 +66,7 @@ type __atomic_exchange_release(volatile type* atomic_obj, type desired); type __atomic_exchange_acq_rel(volatile type* atomic_obj, type desired); type __atomic_exchange_seq_cst(volatile type* atomic_obj, type desired); -<font color="#C80000">// type can be any pod</font> +<font color="#C80000">// type must be trivially copyable</font> bool __atomic_compare_exchange_strong_relaxed_relaxed(volatile type* atomic_obj, type* expected, type desired); @@ -113,7 +116,7 @@ bool __atomic_compare_exchange_strong_seq_cst_seq_cst(volatile type* atomic_obj, type* expected, type desired); -<font color="#C80000">// type can be any pod</font> +<font color="#C80000">// type must be trivially copyable</font> bool __atomic_compare_exchange_weak_relaxed_relaxed(volatile type* atomic_obj, type* expected, type desired); |
