Messages in this thread | | | Date | Fri, 18 Sep 2020 15:09:14 +0200 | From | Oleg Nesterov <> | Subject | Re: [RFC PATCH] locking/percpu-rwsem: use this_cpu_{inc|dec}() for read_count |
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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.
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