[fpc-devel] volatile variables

Michael Schnell mschnell at lumino.de
Thu Jun 30 14:26:39 CEST 2011

On 06/30/2011 11:52 AM, Jonas Maebe wrote:
> On 30 Jun 2011, at 10:38, Michael Schnell wrote:
>> Regarding FPC, TCriticalSection is a decent encapsulation for 
>> pthread_mutex_... when used in this way.
>> But e.g. if you use a TThreadList instance "myList" with multiple 
>> threads it can't be the way to go to include any occurrence of 
>> myList.xxx by a critical section just to make sure that the cache 
>> synchronization has happened and the instance variable itself in fact 
>> is valid.
> That's where optimization comes in,

Very wrong assumption.

Optimization is not the question here it's just working vs. not working.

In a previous post the claim was that if the variable is not in the 
cache of the appropriate CPU, a cache synchronization is not 
automatically done by the underling system (Hardware / OS / Libraries) 
and thus the variable has an erroneous value unless the application 
program uses some special means to provide coherency.

In fact I doubt this, but this was the claim and thus needs to be 
discussed here.


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