On 09/18, Peter Zijlstra wrote: > > On Fri, Sep 18, 2020 at 12:48:24PM +0200, Oleg Nesterov wrote: > > > Of course, this assumes that atomic_t->counter underflows "correctly", just > > like "unsigned int". > > We're documented that we do. Lots of code relies on that. > > See Documentation/atomic_t.txt TYPES Aha, thanks! > > But again, do we really want this? > > I like the two counters better, avoids atomics entirely, some archs > hare horridly expensive atomics (*cough* power *cough*). I meant... do we really want to introduce percpu_up_read_irqsafe() ? Perhaps we can live with the fix from Hou? At least until we find a "real" performance regression. Oleg.
