the kernel executes code on behalf of users all the time. For example, to queue up I/O requests, to read files, to handle network connections, to allocate/free memory, to send signals, and a zillion other things. Many of these operations require modification of something called "a serially-reusable resource" which is just a fancy name for something that can only be used by one user at a time. A stall in a men's restroom is an example. Or, in this case, perhaps it is just a simple linked list. If two processors were to try to insert or remove (or a combination of both) things on a list at the same time, race conditions can arise and the data can become unusable. So we use a spinlock to prevent multiple processors from modifying the same data structure at the same time... Robert M. Hyatt, Ph.D. Computer and Information Sciences hyatt@xxxxxxx University of Alabama at Birmingham (205) 934-2213 136A Campbell Hall (205) 934-5473 FAX Birmingham, AL 35294-1170 On Tue, 4 Sep 2007, Xu Yang wrote: > Hi Robert, > > could you explain more about it, I am quite interested in this. > > thanks, > > regards, > > Yang > > > 2007/9/3, Robert M. Hyatt <hyatt@xxxxxxxxxxx>: > > > > what about the kernel? How will it protect itself when multiple > > processors execute kernel code??? > > > > > > Robert M. Hyatt, Ph.D. Computer and Information Sciences > > hyatt@xxxxxxx University of Alabama at Birmingham > > (205) 934-2213 136A Campbell Hall > > (205) 934-5473 FAX Birmingham, AL 35294-1170 > > > > On Mon, 3 Sep 2007, Xu Yang wrote: > > > > > Hello everyone, > > > > > > Just got a rough question in my head. > > > > > > don't know whether anyone interested . > > > > > > mutex vs cache coherency protocol(for multiprocessor) > > > > > > both of these two can be used to protect shared resource in the memory. > > > > > > are both of them necessary? > > > > > > for example: > > > > > > in a multiprocessor system, if there is only mutex no cache coherency. > > > obviously this would cause problem. > > > > > > what about there is no mutex mechanism, only cache coherency protocol > > > in multiprocessor system? after consideration, I found this also could > > > casue problem, when the processors are multithreading processors, > > > which means more than one threads can be running on one processor. in > > > this case if we only have cache coherency and no mutex, this would > > > cause problem. because all the threads running on one processor share > > > one cache, the cache coherency protocol can not be functioning > > > anymore. the shrared resource could be crashed by different threads. > > > > > > then if all the processors in the multiprocessor system are sigle > > > thread processor, only one thread can be running one one processor. is > > > it ok, if we only have cache coherency protocol ,no mutex mechanism? > > > > > > anyone has any idea? all the comments are welcome and appreciated, > > > including criticism. > > > > > > regards, > > > - > > > To unsubscribe from this list: send the line "unsubscribe linux-smp" in > > > the body of a message to majordomo@xxxxxxxxxxxxxxx > > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > > > > > - To unsubscribe from this list: send the line "unsubscribe linux-smp" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
