Re: [Boost-users] Thread cancellation

From: Ben Hutchings (ben.hutchings_at_[hidden])
Date: 2005-02-11 07:19:00

Paul wrote:
> 
>> Paul,
>>
>> When the flag has changed the memory semantics of your system maybe
>> such that your cpu doesn't see the change for quite a while without
>> memory barriers.
>>
>> If it changes, say flip flops between true and false (not relevant to
>> your case above), then you could end up with different values
>> everywhere at once which may be inconvenient to your programs
>> correctness.
>>
> 
> good lord, assembler?  doesn't the 'volatile' keyword fix the problem 
> you describe?
<snip>

In practice it probably does, but you should be aware that the semantics 
of "volatile" are platform-dependent and generally do not include the 
generation of memory barriers.  In particular pthreads does not assign 
any synchronisation properties to it.

Ben.