Messages in this thread | | | Date | Mon, 15 Jun 2020 14:56:54 +0200 | From | Peter Zijlstra <> | Subject | [PATCH 0/6] sched: TTWU, IPI, and assorted stuff |
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Hi,
So Paul reported rcutorture hitting a NULL dereference, and patch #1 fixes it.
Now, patch #1 is obviously correct, but I can't explain how exactly it leads to the observed NULL pointer dereference. The NULL pointer deref happens in find_matching_se()'s last while() loop when is_same_group() fails even though both parents are NULL.
The only explanation I have for that is that we just did an activate_task() while: 'task_cpu(p) != cpu_of(rq)', because then 'p->se.cfs_rq' doesn't match. However, I can't see how the lack of #1 would lead to that. Never-the-less, patch #2 adds assertions to warn us of this case.
Patch #3 is a trivial rename that ought to eradicate some confusion.
The last 3 patches is what I ended up with for cleaning up the whole smp_call_function/irq_work/ttwu thing more.
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