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| author | Thomas Gleixner <tglx@linutronix.de> | 2024-10-28 11:43:42 +0100 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2024-11-05 12:55:37 +0100 |
| commit | b23decf8ac9102fc52c4de5196f4dc0a5f3eb80b (patch) | |
| tree | c8a60780b61c8c185a8e3a0e74257bcc13aa799a /kernel/sched | |
| parent | sched: psi: pass enqueue/dequeue flags to psi callbacks directly (diff) | |
| download | linux-b23decf8ac9102fc52c4de5196f4dc0a5f3eb80b.tar.xz linux-b23decf8ac9102fc52c4de5196f4dc0a5f3eb80b.zip | |
sched: Initialize idle tasks only once
Idle tasks are initialized via __sched_fork() twice:
fork_idle()
copy_process()
sched_fork()
__sched_fork()
init_idle()
__sched_fork()
Instead of cleaning this up, sched_ext hacked around it. Even when analyis
and solution were provided in a discussion, nobody cared to clean this up.
init_idle() is also invoked from sched_init() to initialize the boot CPU's
idle task, which requires the __sched_fork() invocation. But this can be
trivially solved by invoking __sched_fork() before init_idle() in
sched_init() and removing the __sched_fork() invocation from init_idle().
Do so and clean up the comments explaining this historical leftover.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20241028103142.359584747@linutronix.de
Diffstat (limited to 'kernel/sched')
| -rw-r--r-- | kernel/sched/core.c | 12 |
1 files changed, 5 insertions, 7 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index c57a79e34911..aad48850c1ef 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4423,7 +4423,8 @@ int wake_up_state(struct task_struct *p, unsigned int state) * Perform scheduler related setup for a newly forked process p. * p is forked by current. * - * __sched_fork() is basic setup used by init_idle() too: + * __sched_fork() is basic setup which is also used by sched_init() to + * initialize the boot CPU's idle task. */ static void __sched_fork(unsigned long clone_flags, struct task_struct *p) { @@ -7697,8 +7698,6 @@ void __init init_idle(struct task_struct *idle, int cpu) struct rq *rq = cpu_rq(cpu); unsigned long flags; - __sched_fork(0, idle); - raw_spin_lock_irqsave(&idle->pi_lock, flags); raw_spin_rq_lock(rq); @@ -7713,10 +7712,8 @@ void __init init_idle(struct task_struct *idle, int cpu) #ifdef CONFIG_SMP /* - * It's possible that init_idle() gets called multiple times on a task, - * in that case do_set_cpus_allowed() will not do the right thing. - * - * And since this is boot we can forgo the serialization. + * No validation and serialization required at boot time and for + * setting up the idle tasks of not yet online CPUs. */ set_cpus_allowed_common(idle, &ac); #endif @@ -8561,6 +8558,7 @@ void __init sched_init(void) * but because we are the idle thread, we just pick up running again * when this runqueue becomes "idle". */ + __sched_fork(0, current); init_idle(current, smp_processor_id()); calc_load_update = jiffies + LOAD_FREQ; |