For a shared variable, each thread has a separate instance of it, each tied to a single, hidden variable that holds the value. When reading the tied variable, GET magic locks the hidden variable, copies out its value, then unlocks it. When writing the tied variable, PUT magic locks the hidden variable, replaces its value, then unlocks it. You don't need to do your own locking for threads::shared variables in the simple case.

You need to do locking if you have more than one (GET or PUT) operation and other iThreads might do other (GET or PUT) operations in between in a way that would cause problems. ||= does two operations so it is possible that extra locking needs to be done by the user (when dealing with shared variables). This likely means that even $x++ isn't iThreads safe on shared variables (in any case, I see no evidence of extra magic being implemented in the current threads::shared to make such safe -- probably easiest to do via overloading).

- tye        

In reply to Re^6: is ||= threadsafe? (user locking) by tye
in thread is ||= threadsafe? by perl-diddler

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.