On Mon, Nov 02, 2015 at 07:48:54AM +0000, Vineet Gupta wrote: > Since u bring this up - I think we don't need the original SYNC and/or > SMT thread schedule at all. The SYNC here is a historic relic at best > and we can get rid of it per reasoning below: > > In UP context it is obviously useless, why would we want to stall the > core for all updates to stack memory of t0 to complete before loading > kernel ode callee registers from t1 stack's memory. > > In SMP, we could have a potential race in which outdoing task could be > concurrently picked for running, thus the writes to stack here need to > be visible before the reads from stack on other core. But I think > since this is the same rq, there would be a taken spinlock and once a > core gives it up, an smp barrier would come naturally. > > Peter do u concur ?
I'm still somewhat jet-lagged, but I think the below reference should answer your question: lkml.kernel.org/r/20150917130125.gl3...@twins.programming.kicks-ass.net I (still) need to update that patch and send it out again. But I think it answers your question; we do not rely on arch code to provide barriers for the generic code. Now, if for some reason the arch code has further constraints, then maybe, but I don't think so. -- 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/
