On Wed, May 22, 2019 at 12:54:13PM -0700, Linus Torvalds wrote: > On Wed, May 22, 2019 at 8:40 AM Waiman Long <[email protected]> wrote: > > > > +#if defined(CONFIG_PREEMPT) && \ > > + (defined(CONFIG_DEBUG_PREEMPT) || !defined(CONFIG_X86)) > > +#define lockevent_percpu_inc(x) this_cpu_inc(x) > > +#define lockevent_percpu_add(x, v) this_cpu_add(x, v) > > Why that CONFIG_X86 special case? > > On x86, the regular non-underscore versionm is perfectly fine, and the > underscore is no faster or simpler. > > So just make it be > > #if defined(CONFIG_PREEMPT) > .. non-underscore versions.. > #else > .. underscore versions .. > #endif > > and realize that x86 simply doesn't _care_. On x86, it will be one > single instruction regardless. > > Non-x86 may prefer the underscore versions for the non-preempt case.
To be honest, given this depends on LOCK_EVENT_COUNTS, I'd be inclined to keep things simple and drop the underscore versions entirely. Saves having to worry about things like "could I take an interrupt during the add?". Will
