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sched/walt: check next task state

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Validate that the task selected is in a good state.

on_cpu must not be 1 when picking a task. on_cpu is only
set in prepare_task() just before the task is switched in.

on_rq must not be 0 or migrating when picking a task,
because it must be active.  Only active tasks are
are enqueued on a runqueue, and a migrating task shouldn't
be picked as the rq it is on should be locked doing
the migration.

cpu must be equal to the rq's cpu. pick_next_task must
not be picking a task which is not enqueued in this rq's
cpu.

One exception to the above, is when the scheduler picks
a task that is the same as the previous task. In this case
the task might already be on_cpu.

Change-Id: I07c94c3b2eab0a328222f29550e0515cdcd6e7ed
Signed-off-by: Stephen Dickey <dickey@codeaurora.org>
This commit is contained in:
Stephen Dickey 2021-07-27 08:40:56 -07:00 committed by Rishabh Bhatnagar
parent 179319a53c
commit 5f9174b2f3
1 changed files with 18 additions and 0 deletions
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18
kernel/sched/walt/walt_cfs.c
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@ -1210,6 +1210,15 @@ static void walt_cfs_replace_next_task_fair(void *unused, struct rq *rq, struct
if (unlikely(walt_disabled))
return;
if ((*p) && (*p) != prev && ((*p)->on_cpu == 1 || (*p)->on_rq == 0 ||
(*p)->on_rq == TASK_ON_RQ_MIGRATING ||
(*p)->cpu != cpu_of(rq))) {
printk_deferred("WALT-BUG picked %s(%d) on_cpu=%d on_rq=%d p->cpu=%d cpu_of(rq)=%d kthread=%d\n",
(*p)->comm, (*p)->pid, (*p)->on_cpu,
(*p)->on_rq, (*p)->cpu, cpu_of(rq), ((*p)->flags & PF_KTHREAD));
SCHED_BUG_ON(1);
}
/* We don't have MVP tasks queued */
if (list_empty(&wrq->mvp_tasks))
return;
@ -1222,6 +1231,15 @@ static void walt_cfs_replace_next_task_fair(void *unused, struct rq *rq, struct
*se = &mvp->se;
*repick = true;
if ((*p) && (*p) != prev && ((*p)->on_cpu == 1 || (*p)->on_rq == 0 ||
(*p)->on_rq == TASK_ON_RQ_MIGRATING ||
(*p)->cpu != cpu_of(rq))) {
printk_deferred("WALT-BUG picked %s(%d) on_cpu=%d on_rq=%d p->cpu=%d cpu_of(rq)=%d kthread=%d\n",
(*p)->comm, (*p)->pid, (*p)->on_cpu,
(*p)->on_rq, (*p)->cpu, cpu_of(rq), ((*p)->flags & PF_KTHREAD));
SCHED_BUG_ON(1);
}
trace_walt_cfs_mvp_pick_next(mvp, wts, walt_cfs_mvp_task_limit(mvp));
}