diff options
| author | Valentin Schneider | 2021-05-10 16:10:23 +0100 |
|---|---|---|
| committer | Peter Zijlstra | 2021-05-18 12:53:53 +0200 |
| commit | 00b89fe0197f0c55a045775c11553c0cdb7082fe (patch) | |
| tree | 242f776a1460b80467564ed1156eeacc212dac27 /kernel/sched | |
| parent | fcb501704554eebfd27e3220b0540997fd2b24a8 (diff) | |
sched: Make the idle task quack like a per-CPU kthread
For all intents and purposes, the idle task is a per-CPU kthread. It isn't
created via the same route as other pcpu kthreads however, and as a result
it is missing a few bells and whistles: it fails kthread_is_per_cpu() and
it doesn't have PF_NO_SETAFFINITY set.
Fix the former by giving the idle task a kthread struct along with the
KTHREAD_IS_PER_CPU flag. This requires some extra iffery as init_idle()
call be called more than once on the same idle task.
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210510151024.2448573-2-valentin.schneider@arm.com
Diffstat (limited to 'kernel/sched')
| -rw-r--r-- | kernel/sched/core.c | 21 |
1 files changed, 15 insertions, 6 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 24fd795e4b8c..6a5124c4d54f 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -8234,12 +8234,25 @@ void __init init_idle(struct task_struct *idle, int cpu) __sched_fork(0, idle); + /* + * The idle task doesn't need the kthread struct to function, but it + * is dressed up as a per-CPU kthread and thus needs to play the part + * if we want to avoid special-casing it in code that deals with per-CPU + * kthreads. + */ + set_kthread_struct(idle); + raw_spin_lock_irqsave(&idle->pi_lock, flags); raw_spin_rq_lock(rq); idle->state = TASK_RUNNING; idle->se.exec_start = sched_clock(); - idle->flags |= PF_IDLE; + /* + * PF_KTHREAD should already be set at this point; regardless, make it + * look like a proper per-CPU kthread. + */ + idle->flags |= PF_IDLE | PF_KTHREAD | PF_NO_SETAFFINITY; + kthread_set_per_cpu(idle, cpu); scs_task_reset(idle); kasan_unpoison_task_stack(idle); @@ -8456,12 +8469,8 @@ static void balance_push(struct rq *rq) /* * Both the cpu-hotplug and stop task are in this case and are * required to complete the hotplug process. - * - * XXX: the idle task does not match kthread_is_per_cpu() due to - * histerical raisins. */ - if (rq->idle == push_task || - kthread_is_per_cpu(push_task) || + if (kthread_is_per_cpu(push_task) || is_migration_disabled(push_task)) { /* |