sched/deadline: Fix wrap-around in DL heap
Current code in cpudeadline.c has a bug in re-heapifying when adding a new element at the end of the heap, because a deadline value of 0 is temporarily set in the new elem, then cpudl_change_key() is called with the actual elem deadline as param. However, the function compares the new deadline to set with the one previously in the elem, which is 0. So, if current absolute deadlines grew so much to have negative values as s64, the comparison in cpudl_change_key() makes the wrong decision. Instead, as from dl_time_before(), the kernel should handle correctly abs deadlines wrap-arounds. This patch fixes the problem with a minimally invasive change that forces cpudl_change_key() to heapify up in this case. Signed-off-by: Tommaso Cucinotta <tommaso.cucinotta@sssup.it> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Luca Abeni <luca.abeni@unitn.it> Cc: Juri Lelli <juri.lelli@arm.com> Cc: Juri Lelli <juri.lelli@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1468921493-10054-2-git-send-email-tommaso.cucinotta@sssup.it Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -168,7 +168,7 @@ void cpudl_set(struct cpudl *cp, int cpu, u64 dl, int is_valid)
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if (old_idx == IDX_INVALID) {
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cp->size++;
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cp->elements[cp->size - 1].dl = 0;
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cp->elements[cp->size - 1].dl = dl;
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cp->elements[cp->size - 1].cpu = cpu;
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cp->elements[cpu].idx = cp->size - 1;
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cpudl_change_key(cp, cp->size - 1, dl);
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