On 23.07.2014 15:49, Peter Zijlstra wrote: > On Tue, Jul 22, 2014 at 09:21:40PM -0700, Linus Torvalds wrote: >> On Tue, Jul 22, 2014 at 8:53 PM, Michel Dänzer wrote: >>> >>> Just happened again with the same change on top of 3.16-rc6. >> >> The (maybe) related bugzilla entry is just odd. Bruno Wolff reports >> that the BUG_ON() in his added patch triggers: >> >> + cpumask_clear(sched_group_cpus(sg)); >> + sg->sgc->capacity = 0; >> + BUG_ON(!cpumask_empty(sched_group_cpus(sg))); >> >> where it *just* did a cpumask_clear(), and now the BUG_ON() triggers >> that it's no longer empty? >> >> That would imply an allocation error, but all the sched groups seem to >> be properly allocated with the proper addition of cpumask_size(). >> >> And his config file even has NR_CPUS being 32, so it should be a >> single word of bitmap, which triggers all the simple code. >> >> Completely insane, in other words. > > So we've had this other thread where the same happened: > > lkml.kernel.org/r/20140716145546.GA6922@wolff.to > > (pointed Michel to that earlier) > > And that seems to be sorted now (just found positive feedback in my > Inbox this morning), it was a question of the arch code supplying > completely 'broken' topology information, and the scheduler trusting it > too much. > > The real fix in that thread is: > > lkml.kernel.org/r/20140722133514.GM12054@laptop.lan > > And I'll also add this to make the scheduler less trusting: > > lkml.kernel.org/r/20140722094740.GJ12054@laptop.lan > > Michael, that's not going to tell us what's wrong with your machine, as > you've not got the ancient dual P4 Xeon Bruno's got. Seeing how your > cpuinfo says: > > model name : AMD A10-7850K Radeon R7, 12 Compute Cores 4C+8G > > but we can start the same debugging session I suppose. > > Could you run with this patch on top: > > lkml.kernel.org/r/20140718101633.GP9918@twins.programming.kicks-ass.net > > And provide us with the dmesg after boot? Attached. No FAIL messages yet. -- Earthling Michel Dänzer | http://www.amd.com Libre software enthusiast | Mesa and X developer