07-May-2013 17:25, Andrei Alexandrescu пишет:
On 5/7/13 2:50 AM, Mehrdad wrote:
On Monday, 6 May 2013 at 18:46:56 UTC, Andrei Alexandrescu wrote:
Any concurrent operation (in this case read from one thread and write
from another) requires a handshake between threads, most often in the
form of an release write coupled with an acquire read. Whenever the
handshake is absent but concurrent operations on shared memory do
occur, the code is broken. The beauty of the TLS-based pattern is that
in the steady state there's no need for a shared read and handshake.
Andrei
Hmm, are you referring to the same lack of a barrier that the others are
also referring to?
As far as I can see, there shouldn't be a need for any other handshake
in this example.
As long as the object is fully initialized before _static is written to
(easy enough with just a memory barrier), there is no penalty for
subsequent reads whatsoever.
Right?
No. A tutorial on memory consistency models would be too long to insert
here. I don't know of a good online resource, does anyone?
Sutter's Mill is a good starting point even though it's C++ biased.
Two recent insightful talks on C++11 memory model with down and dirty
details:
http://herbsutter.com/2013/02/11/atomic-weapons-the-c-memory-model-and-modern-hardware/
--
Dmitry Olshansky
--
Dmitry Olshansky
