On 11/11, Frederic Weisbecker wrote: > > On Sat, Nov 09, 2013 at 04:54:28PM +0100, Oleg Nesterov wrote: > > > > Up to you and Suravee, but can't we cleanup this later? > > > > This series was updated many times to address a lot of (sometimes > > contradictory) complaints. > > Sure. But I'm confident that we can solve the conflicting mask / len issue > easily beside. > I mean, I don't feel confident with merging things as is, otoh it should be > easy to fix up.
I do not really understand where do you see the conflict... I can be easily wrong, but afaics currently mask / len issue is simply the implementation detail. > > > I mean, that doesn't look right to me, > > > it's two units basically measuring the same thing, so that's asking for > > > conflicting troubles. > > > > Yes. And we can kill either _len or _mask, not sure what would be more > > clean. > > > > At least with the current implementation (again, iirc) mask == len -1. > > Although amd supports the more generic masks (but I can't recall the > > details). > > Right. I think len is probably more powerful. Unless the mask could be used > to define > multiple ranges of breakpoints, not sure it's ever going to be used that way > though. Actually, mask is more powerfull. And initial versions of this patches (iirc) tried to use mask as an argument which comes from the userspace (tools/perf, perf_event_attr, etc). But one of reviewers nacked this interfacer, so we still use len. > But we > can still extend the interface if we need a mask later. Yes, agreed. > > > I'm just not sure how to reuse the len to express breakpoint ranges (that > > > was in fact the > > > initial purpose of it) without breaking the tools. > > > > Confused... user-space still uses len to express the range? Just > > the kernel "switches" to mask if len > 8 ? > > Right but what if we want breakpoints having a size below 8? Like break on > instructions > from 0x1000 to 0x1008 ? > > Or should we ignore range instruction breakpoints when len < 8? In this case the new code has no effect (iirc), we simply use X86_BREAKPOINT_LEN_* and "tell the hardware about extended range/mask" code is never called. IIRC, currently we simply check bp_mask != 0 to distinguish. Oleg. -- 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/
