On Thu, Sep 27, 2018 at 10:13:15AM +0200, Andrea Parri wrote: > On Thu, Sep 27, 2018 at 09:59:35AM +0200, Peter Zijlstra wrote: > > On Thu, Sep 27, 2018 at 09:47:48AM +0200, Andrea Parri wrote: > > > > LKMM in particular does _NOT_ deal with mixed sized atomics _at_all_. > > > > > > True, but it is nothing conceptually new to deal with: there're Cat > > > models that handle mixed-size accesses, just give it time. > > > > Sure, but until that time I must not rely on (and thus not use) LKMM for > > qspinlock things. > > This is way too generic to be agreed ;D
Only if you know that thing well enough to know why it gives a certain answer, and thus don't already need it. If you need it to help you with something; it can't because it doesn't do the mixed size thing. > > So while your argument about coherence might be true -- I'll have to > > think about it; litmus tests are out the window. > > You trimmed the litmus test I gave you. Because of not wanting to reverse engineer the argument from the litmus test. But yes, I think I see your point, the earlier trylock will load the new value and our later load cannot be earlier than that.