> 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? > > - Where is the integer value physically stored?
could be anywhere within the memory mapped to the kernel memory segment, why do you bother about the physical address ? > - will processor caches and memory management have influence for the > visibillity of the integer value in the second thread? not on UP boxes > > 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? > > 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 > for SMP you have to take care of synchronisation or you will run into problems I would assume that with the setup you described - that is a thread sets a integer and then wakes up a different thread - you would have an implicid synchronization, but any other setup will require explicid protection if you want to be SMP safe. hofrat _______________________________________________ Rtl mailing list [EMAIL PROTECTED] http://www2.fsmlabs.com/mailman/listinfo.cgi/rtl
