Messages in this thread | | | Date | Thu, 7 Nov 2019 19:27:53 +0000 | From | Quentin Perret <> | Subject | Re: NULL pointer dereference in pick_next_task_fair |
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On Thursday 07 Nov 2019 at 19:43:56 (+0100), Peter Zijlstra wrote: > But you mean something like: > > for (class = prev->sched_class; class; class = class->next) { > if (class->balance(rq, rf)) > break; > } > > put_prev_task(rq, prev); > > for_each_class(class) { > p = class->pick_next_task(rq); > if (p) > return p; > } > > BUG(); > > like?
Right, something like that, though what I had was basically doing the pull from within the pick_next_task_*() functions directly, like we were doing before. I'm now seeing how easy it is to get this wrong, and that even good-looking code in this area can be broken in very subtle ways, so I didn't feel comfortable refactoring again so close to rc7. If you feel more confident, I'm more than happy to test a patch implemeting the above :)
> I had convinced myself we didn't need that, but that DL to RT case is > pesky and might require it after all.
Yep, I don't see a way to avoid iterating all classes to do the balance, one way or another ...
Thanks, Quentin
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