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authorThomas Gleixner <tglx@linutronix.de>2024-10-28 11:43:42 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2024-12-06 07:20:46 +0100
commite80e6c1b93c455bd831628aaa23d9fd93f826648 (patch)
treec9ade4914cdf080567719448c7649ae2b07c3e63
parentfa10f348fd80c7ea7b7c0a7763ba7c0bf1a16be3 (diff)
sched: Initialize idle tasks only once
commit b23decf8ac9102fc52c4de5196f4dc0a5f3eb80b upstream. 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 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--kernel/sched/core.c12
1 files changed, 5 insertions, 7 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index a1c353a62c56..76b27b2a9c56 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4424,7 +4424,8 @@ 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)
{
@@ -7683,8 +7684,6 @@ 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);
@@ -7699,10 +7698,8 @@ 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
@@ -8546,6 +8543,7 @@ 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;