Jan Hudec <bulb@cimice.maxinet.cz> wrote:
>On Wed, Aug 28, 2002 at 08:34:25PM +0200, Bernd Petrovitsch wrote:
[...]
>> Any variable that may change it's value without code at that place
>> should be volatile (i.e. hardware status registers and similar,
>> variables changed by signal handlers, etc.).
>> Otherwise the C compiler is allowed to assume that the variable's
>> contents works like RAM and use that wisdom.
>
>Well, every variable that may change without code being in place must in
>first place be locked or operated using atomic operations. And these
ACK, but this has nothing to do with "volatile" and it's definition in
(ANSI-)C which is required here.
IOW : doing
---- snip ----
int x = 0; /* no volatile here */
...
while (x == 0) {
sleep(1);
}
....
---- snip ----
and waiting for x to change through some other means (as said above
e.g. signal handlers) may not work.
And it basically has nothing to do with barriers and the like on
simple uniprocessor sytems.
Bernd
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