Messages in this thread Patch in this message | | | Subject | Re: [PATCH v8 -tip 02/26] sched: Introduce sched_class::pick_task() | From | Vineeth Pillai <> | Date | Sat, 24 Oct 2020 07:10:26 -0400 |
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Hi Aubrey,
On 10/23/20 10:48 PM, Li, Aubrey wrote: > >>>> 2. Do you see the issue in v7? Not much if at all has changed in this >>>> part of the code from v7 -> v8 but could be something in the newer >>>> kernel. >>>> >>> IIRC, I can run uperf successfully on v7. >>> I'm on tip/master 2d3e8c9424c9 (origin/master) "Merge branch 'linus'." >>> Please let me know if this is a problem, or you have a repo I can pull >>> for testing. >> Here is a repo with v8 series on top of v5.9 release: >> https://git.kernel.org/pub/scm/linux/kernel/git/jfern/linux.git/log/?h=coresched-v5.9 > I didn't see NULL pointer dereference BUG of this repo, will post performance > data later. There has been a change in tip in pick_next_entity which caused removal of a coresched related change to fix the crash. Could you please try this patch on top of the posted v8 and see if this works?
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 93a3b874077d..4cae5ac48b60 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4428,12 +4428,14 @@ pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr) se = second; }
- if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1) { + if (left && cfs_rq->next && + wakeup_preempt_entity(cfs_rq->next, left) < 1) { /* * Someone really wants this to run. If it's not unfair, run it. */ se = cfs_rq->next; - } else if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1) { + } else if (left && cfs_rq->last && + wakeup_preempt_entity(cfs_rq->last, left) < 1) { /* * Prefer last buddy, try to return the CPU to a preempted task.
There reason for left being NULL needs to be investigated. This was there from v1 and we did not yet get to it. I shall try to debug later this week.
Kindly test this patch and let us know if it fixes the crash.
Thanks, Vineeth
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