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Re: [doc, rfa] (v2) improve x86 transactional memory intrinsics section



On 02/24/2015 01:51 AM, Sandra Loosemore wrote:
On 02/23/2015 03:36 AM, Patrick Marlier wrote:
On 02/22/2015 04:06 AM, Sandra Loosemore wrote:

+Here is an example showing handling for @code{_XABORT_RETRY}
+and a fallback path for other failures:
+
+@smallexample
+#include <immintrin.h>
+
+int n_tries, max_tries;
+unsigned status = _XBEGIN_STARTED;

I would suggest to set it to something different. Indeed if max_tries ==
0, then it will end up to do the transactional code with no transaction
started.

Good catch....

+...
+
+for (n_tries = 0; n_tries < max_tries; n_tries++)
+  @{
+    status = _xbegin ();
+    if (status == _XBEGIN_STARTED || !(status | _XABORT_RETRY))

Should not be || !(status & _XABORT_RETRY) ?

Yup, that was a think-o.

+      break;
+  @}
+if (status == _XBEGIN_STARTED)
+  @{
+    ... transaction code...
+    _xend ();
+  @}
+else
+  @{
+    ... non transactional fallback path...
+  @}
+@end smallexample

Thanks a lot. It gives a good idea on how to use it. I just would like
to mention that the non transactional and transactional code must
synchronize together (in most cases) to ensure consistency.

OK, I added a sentence about that.

Revised patch attached.  OK to commit this version?

-Sandra


_XBEGIN_EXPLICIT does not exist right? maybe 0 is better to avoid confusion? or ~_XBEGIN_STARTED?
But it sounds good to me. Thanks.
--
Patrick


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