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Re: Question on volatile functions and GCC

From: Ian Lance Taylor <iant at google dot com>
To: David Paterson <dnpaterson at gmail dot com>
Cc: Jonathan Wakely <jwakely dot gcc at gmail dot com>, noloader at gmail dot com, gcc-help at gcc dot gnu dot org
Date: Tue, 5 Mar 2013 06:35:00 -0800
Subject: Re: Question on volatile functions and GCC
References: <CAH8yC8=iFF-74qkAoTyEVSWnTKaKcZAtGfj+eRHQj1WMa0A4zg@mail.gmail.com> <CAM1kHc2Xuwnpjg1pAL7jBRHhpsrSeqYAjyDVC6UWpXub1YLHeQ@mail.gmail.com> <CAH6eHdTpzzHjzi+n2=ESDP=eDm060x_Cs4MXpJ_WNHOjKKShzw@mail.gmail.com> <CAM1kHc2Z_ZVurbK8YnbtDRghvkBf_6aQOy5nzCXo-U3aiTw7hA@mail.gmail.com>

On Tue, Mar 5, 2013 at 1:58 AM, David Paterson <dnpaterson@gmail.com> wrote:
> On 5 March 2013 09:40, Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
>
>> volatile is not for multithreading, you need proper synchronization
>> for interthread communication.
>
> Not always.  For very simple, non-critical uses you can just use a
> volatile flag-type variable.  Cheap and nasty, I agree, but useable.

If your code has a race condition before you add a volatile qualifier,
it will still have a race condition after you add the qualifier.

If you want a simple flag variable, don't use volatile; use
__atomic_load and __atomic_store.

Ian

References:
- Question on volatile functions and GCC
  - From: Jeffrey Walton
- Re: Question on volatile functions and GCC
  - From: David Paterson
- Re: Question on volatile functions and GCC
  - From: Jonathan Wakely
- Re: Question on volatile functions and GCC
  - From: David Paterson

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