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Commit 970c305a authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull scheduler fix from Thomas Gleixner:
 "A single scheduler fix:

  Prevent idle task from ever being preempted. That makes sure that
  synchronize_rcu_tasks() which is ignoring idle task does not pretend
  that no task is stuck in preempted state. If that happens and idle was
  preempted on a ftrace trampoline the machine crashes due to
  inconsistent state"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/core: Call __schedule() from do_idle() without enabling preemption
parents e7a3d627 8663effb

kernel/sched/core.c

+25 −0
Original line number Diff line number Diff line
@@ -3502,6 +3502,31 @@ asmlinkage __visible void __sched schedule(void) 
}

EXPORT_SYMBOL(schedule);



/*

 * synchronize_rcu_tasks() makes sure that no task is stuck in preempted

 * state (have scheduled out non-voluntarily) by making sure that all

 * tasks have either left the run queue or have gone into user space.

 * As idle tasks do not do either, they must not ever be preempted

 * (schedule out non-voluntarily).

 *

 * schedule_idle() is similar to schedule_preempt_disable() except that it

 * never enables preemption because it does not call sched_submit_work().

 */

void __sched schedule_idle(void)

{

	/*

	 * As this skips calling sched_submit_work(), which the idle task does

	 * regardless because that function is a nop when the task is in a

	 * TASK_RUNNING state, make sure this isn't used someplace that the

	 * current task can be in any other state. Note, idle is always in the

	 * TASK_RUNNING state.

	 */

	WARN_ON_ONCE(current->state);

	do {

		__schedule(false);

	} while (need_resched());

}



#ifdef CONFIG_CONTEXT_TRACKING

asmlinkage __visible void __sched schedule_user(void)

{

kernel/sched/idle.c

+1 −1
Original line number Diff line number Diff line
@@ -265,7 +265,7 @@ static void do_idle(void) 
	smp_mb__after_atomic();



	sched_ttwu_pending();

	schedule_preempt_disabled();

	schedule_idle();



	if (unlikely(klp_patch_pending(current)))

		klp_update_patch_state(current);

kernel/sched/sched.h

+2 −0
Original line number Diff line number Diff line
@@ -1467,6 +1467,8 @@ static inline struct cpuidle_state *idle_get_state(struct rq *rq) 
}

#endif



extern void schedule_idle(void);



extern void sysrq_sched_debug_show(void);

extern void sched_init_granularity(void);

extern void update_max_interval(void);