On Wed, Aug 28, 2002 at 02:54:47PM -0600, Tom Bradley wrote: > > Well, every variable that may change without code being in place must in > > first place be locked or operated using atomic operations. And these > > NO! > > Locks are used to keep two pieces of code from accessing a variable at the > same time, nothing to do with cached values. I.e. the Reader/Writer > problem. Atomic operations state that this operation is gaurenteed to > complete without interuption, atomic variables are volatile, and are > used to perform locks. Locks around a variable DO NOT gaurentee you are > getting the latest value, you can still be getting a cached value. Locks, at least in kernel DO guarantee you are geting the latest value because they are defined to be optimization barriers. Locks or atomic operations are only way to ensure you don't get garbage. Consider loading sparc register with constant, when you only have 16 bits for an operand in each instruction. ------------------------------------------------------------------------------- Jan 'Bulb' Hudec <bulb@ucw.cz> -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
