On Tue, Aug 21, 2007 at 01:02:01AM +0200, Segher Boessenkool wrote: > >>And no, RMW on MMIO isn't "problematic" at all, either. > >> > >>An RMW op is a read op, a modify op, and a write op, all rolled > >>into one opcode. But three actual operations. > > > >Maybe for some CPUs, but not all. ARM for instance can't use the > >load exclusive and store exclusive instructions to MMIO space. > > Sure, your CPU doesn't have RMW instructions -- how to emulate > those if you don't have them is a totally different thing.
Let me say it more clearly: On ARM, it is impossible to perform atomic operations on MMIO space. -- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
