Messages in this thread | | | Date | Fri, 23 Oct 2020 17:47:02 -0400 | From | Joel Fernandes <> | Subject | Re: [PATCH v8 -tip 02/26] sched: Introduce sched_class::pick_task() |
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On Fri, Oct 23, 2020 at 01:25:38PM +0800, Li, Aubrey wrote: > >>> @@ -2517,6 +2528,7 @@ const struct sched_class dl_sched_class > >>> > >>> #ifdef CONFIG_SMP > >>> .balance = balance_dl, > >>> + .pick_task = pick_task_dl, > >>> .select_task_rq = select_task_rq_dl, > >>> .migrate_task_rq = migrate_task_rq_dl, > >>> .set_cpus_allowed = set_cpus_allowed_dl, > >>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > >>> index dbd9368a959d..bd6aed63f5e3 100644 > >>> --- a/kernel/sched/fair.c > >>> +++ b/kernel/sched/fair.c > >>> @@ -4450,7 +4450,7 @@ pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr) > >>> * Avoid running the skip buddy, if running something else can > >>> * be done without getting too unfair. > >>> */ > >>> - if (cfs_rq->skip == se) { > >>> + if (cfs_rq->skip && cfs_rq->skip == se) { > >>> struct sched_entity *second; > >>> > >>> if (se == curr) { > >>> @@ -6976,6 +6976,35 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_ > >>> set_last_buddy(se); > >>> } > >>> > >>> +#ifdef CONFIG_SMP > >>> +static struct task_struct *pick_task_fair(struct rq *rq) > >>> +{ > >>> + struct cfs_rq *cfs_rq = &rq->cfs; > >>> + struct sched_entity *se; > >>> + > >>> + if (!cfs_rq->nr_running) > >>> + return NULL; > >>> + > >>> + do { > >>> + struct sched_entity *curr = cfs_rq->curr; > >>> + > >>> + se = pick_next_entity(cfs_rq, NULL); > >>> + > >>> + if (curr) { > >>> + if (se && curr->on_rq) > >>> + update_curr(cfs_rq); > >>> + > >>> + if (!se || entity_before(curr, se)) > >>> + se = curr; > >>> + } > >>> + > >>> + cfs_rq = group_cfs_rq(se); > >>> + } while (cfs_rq); > >>> ++ > >>> + return task_of(se); > >>> +} > >>> +#endif > >> > >> One of my machines hangs when I run uperf with only one message: > >> [ 719.034962] BUG: kernel NULL pointer dereference, address: 0000000000000050 > >> > >> Then I replicated the problem on my another machine(no serial console), > >> here is the stack by manual copy. > >> > >> Call Trace: > >> pick_next_entity+0xb0/0x160 > >> pick_task_fair+0x4b/0x90 > >> __schedule+0x59b/0x12f0 > >> schedule_idle+0x1e/0x40 > >> do_idle+0x193/0x2d0 > >> cpu_startup_entry+0x19/0x20 > >> start_secondary+0x110/0x150 > >> secondary_startup_64_no_verify+0xa6/0xab > > > > Interesting. Wondering if we screwed something up in the rebase. > > > > Questions: > > 1. Does the issue happen if you just apply only up until this patch, > > or the entire series? > > I applied the entire series and just find a related patch to report the > issue.
Ok.
> > 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
thanks,
- Joel
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