diff options
Diffstat (limited to 'libcxx/www/atomic_design.html')
| -rw-r--r-- | libcxx/www/atomic_design.html | 34 |
1 files changed, 34 insertions, 0 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> |
