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<p>Really, insofar as x86 is concerned, the only ones that are
guaranteed to be atomic are, I think, the ordinal types, but that
still leaves problems of code such as the following:</p>
<p>if GlobalCounter = 10 then<br>
begin<br>
DoSomething;<br>
Break;<br>
end else<br>
Inc(GlobalCounter);</p>
<p>If two threads are running a loop with the following code at the
end, it could be that GlobalCounter is 9, the condition is
checked, but before Inc(GlobalCounter) is called, the scheduler
switches to the other thread, where GlobalCounter is checked and
is still 9, and is then incremented, and only then does it switch
back to the other thread, where Inc(GlobalCounter) is finally
called, thereby setting GlobalCounter to 11 and breaking the
program.</p>
<p>In this instance, a critical section or some other mutex is
required, or the interlocked instructions, all of which incur a
performance penalty.</p>
<p>Definitely something for a lot of discussion!<br>
</p>
<p>Gareth aka. Kit</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 02/07/2019 08:13, Benito van der
Zander wrote:<br>
</div>
<blockquote type="cite"
cite="mid:cbee0e5f-e9e5-cea2-dced-d9722c779db0@benibela.de">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<div id="smartTemplate4-template">Hi,<br>
<br>
<div class="moz-cite-prefix">Am 28.06.19 um 11:24 schrieb George
Bakhtadze:<br>
</div>
<blockquote type="cite"
cite="mid:1455841561713884@iva8-bad53723c646.qloud-c.yandex.net">
<div>If FPC somehow guarantees that a global field (even only
of simple types) can be atomically read and written from any
thread for ANY platform that is a very strong guarantee and
worth mention in documentation.</div>
</blockquote>
<p> btw, how would you do that if it is in not guaranteed?
especially on arm<br>
</p>
Are there functions to do only an atomic reads and writes?
(besides functions like interlockedincrement that do both, a
read and write, together)<br>
<br>
Best,<br>
Benito <br>
</div>
<br>
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