On Tue, Apr 23, 2019 at 03:12:16PM -0400, Waiman Long wrote: > On 4/23/19 12:27 PM, Linus Torvalds wrote: > > On Tue, Apr 23, 2019 at 7:17 AM Peter Zijlstra <pet...@infradead.org> wrote: > >> I'm not aware of an architecture where disabling interrupts is faster > >> than disabling preemption. > > I don't thin kit ever is, but I'd worry a bit about the > > preempt_enable() just because it also checks if need_resched() is true > > when re-enabling preemption. > > > > So doing preempt_enable() as part of rwsem_read_trylock() might cause > > us to schedule in *exactly* the wrong place, > > You are right on that. However, there is a variant called > preempt_enable_no_resched() that doesn't have this side effect. So I am > going to use that one instead.
Only if the very next line is schedule(). Otherwise you're very much not going to use that function.
