On Wed 2014-05-07 22:26:55, Borislav Petkov wrote: > On Wed, May 07, 2014 at 10:22:33PM +0200, Thomas Gleixner wrote: > > On Wed, 7 May 2014, Andrew Morton wrote: > > > On Wed, 7 May 2014 21:57:41 +0200 Borislav Petkov <b...@alien8.de> wrote: > > > > > > > We have all those eager tester dudes which scratch up a dirty script to > > > > pound on CPU hotplug senselessly and then report bugs they've managed to > > > > trigger. > > > > > > > > Well, first of all, most, if not all, bugs they trigger are CPU hotplug > > > > related anyway. But we know hotplug is full of duct tape and brown > > > > paper bags. So we end up clearly wasting too much time dealing with a > > > > mechanism we know it is b0rked in the first place. > > > > > > > > Oh, and I would understand if that pounding were close to some real > > > > usage patterns but I've yet to receive a justification for toggling > > > > cores on- and offline senselessly. > > > > > > > > In any case, before this gets rewritten properly (I'm being told we > > > > might get lucky after all) let's slow down hotplugging on purpose and > > > > thus make it uninteresting, as a temporary brown paper bag solution > > > > until the real thing gets done. > > > > > > > > This way we'll save us a lot of time and efforts in chasing the wrong > > > > bugs. > > > > > > Well, I only yesterday merged Srivatsa's `CPU hotplug, stop-machine: > > > plug race-window that leads to "IPI-to-offline-CPU"' bugfix. That bug > > > presumably wouldn't have been fixed if this patch was in place. > > > > True. > > > > OTOH, if people would have spent the same amount of time to rewrite > > the hotplug mess, we would have a way bigger benefit. But no, we > > prefer to add more layers of duct tape and bandaid hackery to it. > > > > I tried a redesign and run out of cycles, but the patches are out > > there and none of the folks who promised to complete them ever > > delivered. If nothing fundamental changes, I'm going to spend some > > serious time on it in the next couple of month. > > ... and in the interim, we could slow down the duct tape and bandaid > hackery until it gets rewritten properly. The ever increasing in > complexity bugfixes say exactly that - it needs a long hard look and a > rewrite.
Well. If you add the delay, you'll mask real problems and cause regressions when the delay is removed -- because fix-hotplug will probably take time to get right. Bad idea, AFAICT. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- 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/