On Mon, Oct 19, 2015 at 04:21:08PM +0100, Catalin Marinas wrote: > On Mon, Oct 19, 2015 at 09:06:05AM +0200, Ingo Molnar wrote: > > * Peter Zijlstra <[email protected]> wrote: > > > > > In any case, its all moot now, since Paul no longer requires schedule() > > > to imply > > > a full barrier. > > > > > > [...] > > > > Nevertheless from a least-surprise POV it might be worth guaranteeing it, > > because > > I bet there's tons of code that assumes that schedule() is a heavy > > operation and > > it's such an easy mistake to make. Since we are so close to having that > > guarantee, > > we might as well codify it? > > FWIW, the arm64 __switch_to() has a heavy barrier (DSB) but the reason > for this was to cope with potentially interrupted cache or TLB > maintenance (which require a DSB on the same CPU) and thread migration > to another CPU.
Right, but there's a path through schedule() that does not pass through __switch_to(); when we pick the current task as the most eligible task and next == prev. In that case there really only is the wmb, a spin lock, an atomic op and a spin unlock (and a whole bunch of 'normal' code of course). -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
