Commit 18f08dae authored Aug 04, 2017 by Cheng Jian Committed by Ingo Molnar Aug 10, 2017

sched/core: Remove unnecessary initialization init_idle_bootup_task()



init_idle_bootup_task( ) is called in rest_init( ) to switch
the scheduling class of the boot thread to the idle class.

the function only sets:

    idle->sched_class = &idle_sched_class;

which has been set in init_idle() called by sched_init():

    /*
     * The idle tasks have their own, simple scheduling class:
     */
    idle->sched_class = &idle_sched_class;

We've already set the boot thread to idle class in
start_kernel()->sched_init()->init_idle()
so it's unnecessary to set it again in
start_kernel()->rest_init()->init_idle_bootup_task()

Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>
Signed-off-by: Xie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <akpm@linux-foundation.org>
Cc: <huawei.libin@huawei.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1501838377-109720-1-git-send-email-cj.chengjian@huawei.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 3261ed0b

include/linux/sched/task.h

+0 −1

Original line number	Diff line number	Diff line
		@@ -30,7 +30,6 @@ extern int lockdep_tasklist_lock_is_held(void);

		extern asmlinkage void schedule_tail(struct task_struct *prev);
		extern void init_idle(struct task_struct *idle, int cpu);
		extern void init_idle_bootup_task(struct task_struct *idle);

		extern int sched_fork(unsigned long clone_flags, struct task_struct *p);
		extern void sched_dead(struct task_struct *p);

init/main.c

+0 −1

Original line number	Diff line number	Diff line
		@@ -430,7 +430,6 @@ static noinline void __ref rest_init(void)
		* The boot idle thread must execute schedule()
		* at least once to get things moving:
		*/
		init_idle_bootup_task(current);
		schedule_preempt_disabled();
		/* Call into cpu_idle with preempt disabled */
		cpu_startup_entry(CPUHP_ONLINE);

kernel/sched/core.c

+0 −5

Original line number	Diff line number	Diff line
		@@ -5177,11 +5177,6 @@ void show_state_filter(unsigned long state_filter)
		debug_show_all_locks();
		}

		void init_idle_bootup_task(struct task_struct *idle)
		{
		idle->sched_class = &idle_sched_class;
		}

		/**
		* init_idle - set up an idle thread for a given CPU
		* @idle: task in question

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