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From: Alexander Terekhov <terekhov@web.de>
Newsgroups: comp.programming.threads
Subject: Re: cond signal wait
Date: Wed, 25 May 2011 19:16:00 +0200
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Anthony Williams wrote:

[...]

> void signaller()
> {
>         lock mutex;
>         // if we get here, waiter() hasn't yet executed **A**
>         // or is blocked in **B**, so will be woken by signal
>         // or has executed line **C** so doesn't care about signal
>         mark data as ready;
>         signal condvar;
>         unlock mutex;
> }
          lock mutex;
          // if we get here, waiter() hasn't yet executed **A**
          // or is blocked in **B**, so will be woken by signal
          // or has executed line **C** so doesn't care about signal
          mark data as ready;
          unlock mutex;
          signal condvar;

is the regular case.

signalling prior to unlock is special.

regards,
alexander.