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Updated atomic design docs

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git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@116065 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Howard Hinnant 2010-10-08 17:36:50 +00:00
parent ffb9a4e235
commit 08f2969220
3 changed files with 45 additions and 5 deletions
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34
www/atomic_design.html
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@ -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&lt;long long&gt; A;
int foo() { return A.compare_exchange_strong(w, x); }
TU2.cc
-----------
extern atomic&lt;long long&gt; 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>

3
www/atomic_design_a.html
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@ -49,6 +49,9 @@ the memory ordering parameter.
<font color="#C80000">// In every intrinsic signature below, type* atomic_obj may be a pointer to a</font>
<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);

13
www/atomic_design_b.html
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@ -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);