On Wed, Jul 23, 2014 at 10:26:21AM -0700, Linus Torvalds wrote: > On Wed, Jul 23, 2014 at 10:12 AM, Linus Torvalds > <torva...@linux-foundation.org> wrote: > > > > sched_init() definitely does _not_ allocate a cpumask_var. > > Side note: another good rule of thumb for per-cpu variables is: > > - if you use __get_cpu_var() without taking the address of it, you're > doing something wrong and stupid. > > The whole - and really *only* - point of __get_cpu_var is to get the > address of a a cpu variable. If you want to read the *value* of the > variable, you should use "this_cpu_read()", which can use things like > special instructions or segments to read the percpu area.
I think this code predates all the this_cpu* magic. But yes, agreed. > I agree that the interface is not all that great, there's historical > baggage there. We would have been better off with > "__this_cpu_ptr(var)" instead of "&__get_cpu_var(var)". But that > "__get_cpu_var()" is the old way of doing things (predating the new > and better "this_cpu_read/write/ops()" stuff), which is why we have > that odd interface with "&__get_cpu_var()". I think there's a whole bunch of patches by Christoph Lameter, queued by TJ that remove all __get_cpu_var usage and eventually the interface. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
