On Tue, Mar 04, 2008 at 04:16:33AM +1100, Nick Piggin wrote: > On Tuesday 04 March 2008 02:53, Alan Cox wrote: > > > Atomicity of reads of write for pointers and integral types (other than > > > long long) should be documented. > > > > NAK. > > > > Atomicity of reads or writes for pointers and integral types is NOT > > guaranteed. Gcc doesn't believe in your guarantee. > > Are you sure gcc doesn't? Or is it just "C"? > > Linux wouldn't work today if gcc did something non-atomic there > (presuming you're talking about naturally aligned pointers/ints). > It is widely used and accepted. > > RCU users are far from the only places to rely on this, although > I guess they are the main ones when it comes to assigning pointers > atomically. It is true that gcc can refetch pointers/ints if it runs out of registers, which is why rcu_dereference() recently had an ACCESS_ONCE() added to it. But such refetching cannot result in a mish-mash of two different pointer values, confusing though it might be to the affected code. Thanx, Paul _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
