On Tuesday 15 October 2002 23:09, Thomas Sauter wrote: > Hi RTL-Folks, > > Does somebody have some answers for the following question? > > You have two RTL threads and a global integer variable which is initial > set to zero. > > Thread one will change the global integer variable without the use of > any synchronisation mechanism to a new value. After that, thread one > will wakeup thread two and suspend himself. > > Now the question: > > What value will thread two see in the global integer variable after the > wakeup - zero or the new value set by thread one? the new value
> - Where is the integer value physically stored? somewhere in the kernel memory - so take care about not writing off-shore! > - will processor caches and memory management have influence for the > visibillity of the integer value in the second thread? Shouldn't, if the caches work correctly (which they do 99.999% of the time) > With other words can i assume that the change of an integer variable is > an atomic instruction, or is it necessary to use a mutex for write and > read operations off integers to be shure that global interger data is > recent in all threads? Hmm, depends a bit on what you want to do... if you can be assured of the correct run-time order, you don't need to protect this memory. Protection is only needed when you're not sure who will be accessing this memory-location next... > What about the use of memory barriers in RTL-Threads? ???? > In the moment i use a single processor Athlon XP 2GHz, but i like to > keep code portable to other processors and multiprocessor environments That's a very good thing. Although, going from a multi-threaded to a multi-processor environment shouldn't be different. Shouldn't... > sorry for cunfusing you, Sorry to clean things up ;-) Linus -- ------------------------------------------------------------- Linus Gasser EPFL Phone: +41 21 693 5635 Mobile Communications Lab. FAX : +41 21 693 4312 CH-1015 Lausanne email: [EMAIL PROTECTED] SWITZERLAND WEB : http://lcmwww.epfl.ch ------------------------------------------------------------- _______________________________________________ Rtl mailing list [EMAIL PROTECTED] http://www2.fsmlabs.com/mailman/listinfo.cgi/rtl
