On Thu, 14 Dec 2023 12:50:29 -0800 Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > > But do all archs have an implementation of cmpxchg64, even if it requires > > disabling interrupts? If not, then I definitely cannot remove this code. > > We have a generic header file, so anybody who uses that would get the > fallback version, ie > > arch_cmpxchg64 -> generic_cmpxchg64_local -> __generic_cmpxchg64_local > > which does that irq disabling thing. > > But no, not everybody is guaranteed to use that fallback. From a quick > look, ARC, hexagon and CSky don't do this, for example. > > And then I got bored and stopped looking. > > My guess is that *most* 32-bit architectures do not have a 64-bit > cmpxchg - not even the irq-safe one. OK, that means I have to completely abandon this change, even for the next merge window. I may add a check if cmpxchg64 exists before falling back to the 32bit cmpxchg version. But even that will have to wait till the next merge window, with a fixes tag (but not Cc'd stable) in case anyone would like to backport it. Thanks for the advice! -- Steve
