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On 06/27/2011 03:31 PM, Andrew Brunner wrote:<br>
<blockquote
cite="mid:BANLkTimjmyJBWQp6c2_T4jFYuvq50g4Xgg@mail.gmail.com"
type="cite">
<pre wrap="">
Simply protecting a loop with a futex is not sufficient. Assigning
variables in a multi-threaded environment is not sufficient.
</pre>
</blockquote>
While I don't think we should this discuss in this context, I
suggest that in the docs for the user of the object library (that
was the starting point of the discussion), any type of thread-safety
should include threads running on multiple processors.<br>
<blockquote
cite="mid:BANLkTimjmyJBWQp6c2_T4jFYuvq50g4Xgg@mail.gmail.com"
type="cite">
<pre wrap="">
Interlocked/Exchange/ExchangeAdd/Increment features must be used
whenever dealing with variables (with at least one exception) In my
experience arrays of boolean are atomic.
</pre>
</blockquote>
Yep. But this is only relevant if you don't protect them by a
critical section, as this excludes concurrent exchange before the
critical instructions are executed. Of course (when possible) using
the interlocked instruction results in a lot less overhead than
simply using a critical section.<br>
<blockquote
cite="mid:BANLkTimjmyJBWQp6c2_T4jFYuvq50g4Xgg@mail.gmail.com"
type="cite">
<pre wrap="">
I ran tests on a HexCore AMD system which had unexplained anomalies
with pointers in an bidirectional linked list. I replaced all the
pointer assignments with InterlockedExchange and the system worked
flawlessly. </pre>
</blockquote>
This is clear. You also would have been able to avoid the problem by
using critical sections around <b>all </b>the appropriate
instructions, but supposedly this would have slowed done the
application greatly. <br>
<blockquote
cite="mid:BANLkTimjmyJBWQp6c2_T4jFYuvq50g4Xgg@mail.gmail.com"
type="cite">
<pre wrap=""> Some of the assignments were taking place in a
criticalsection (btw).
</pre>
</blockquote>
I believe that the "some" were not enough.<br>
<br>
-Michael<br>
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