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Commit f5fa3630 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 fixes from Ingo Molnar:
 "Various scheduler fixes all over the place: three SCHED_DL fixes,
  three sched/numa fixes, two generic race fixes and a comment fix"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/dl: Fix preemption checks
  sched: Update comments for CLONE_NEWNS
  sched: stop the unbound recursion in preempt_schedule_context()
  sched/fair: Fix division by zero sysctl_numa_balancing_scan_size
  sched/fair: Care divide error in update_task_scan_period()
  sched/numa: Fix unsafe get_task_struct() in task_numa_assign()
  sched/deadline: Fix races between rt_mutex_setprio() and dl_task_timer()
  sched/deadline: Don't replenish from a !SCHED_DEADLINE entity
  sched: Fix race between task_group and sched_task_group
parents 5656b408 f3a7e1a9

arch/x86/include/asm/preempt.h

+1 −0
Original line number Diff line number Diff line
@@ -105,6 +105,7 @@ static __always_inline bool should_resched(void) 
# ifdef CONFIG_CONTEXT_TRACKING

    extern asmlinkage void ___preempt_schedule_context(void);

#   define __preempt_schedule_context() asm ("call ___preempt_schedule_context")

    extern asmlinkage void preempt_schedule_context(void);

# endif

#endif

include/uapi/linux/sched.h

+1 −1
Original line number Diff line number Diff line
@@ -13,7 +13,7 @@ 
#define CLONE_VFORK	0x00004000	/* set if the parent wants the child to wake it up on mm_release */

#define CLONE_PARENT	0x00008000	/* set if we want to have the same parent as the cloner */

#define CLONE_THREAD	0x00010000	/* Same thread group? */

#define CLONE_NEWNS	0x00020000	/* New namespace group? */

#define CLONE_NEWNS	0x00020000	/* New mount namespace group */

#define CLONE_SYSVSEM	0x00040000	/* share system V SEM_UNDO semantics */

#define CLONE_SETTLS	0x00080000	/* create a new TLS for the child */

#define CLONE_PARENT_SETTID	0x00100000	/* set the TID in the parent */

kernel/context_tracking.c

+0 −40
Original line number Diff line number Diff line
@@ -107,46 +107,6 @@ void context_tracking_user_enter(void) 
}

NOKPROBE_SYMBOL(context_tracking_user_enter);



#ifdef CONFIG_PREEMPT

/**

 * preempt_schedule_context - preempt_schedule called by tracing

 *

 * The tracing infrastructure uses preempt_enable_notrace to prevent

 * recursion and tracing preempt enabling caused by the tracing

 * infrastructure itself. But as tracing can happen in areas coming

 * from userspace or just about to enter userspace, a preempt enable

 * can occur before user_exit() is called. This will cause the scheduler

 * to be called when the system is still in usermode.

 *

 * To prevent this, the preempt_enable_notrace will use this function

 * instead of preempt_schedule() to exit user context if needed before

 * calling the scheduler.

 */

asmlinkage __visible void __sched notrace preempt_schedule_context(void)

{

	enum ctx_state prev_ctx;



	if (likely(!preemptible()))

		return;



	/*

	 * Need to disable preemption in case user_exit() is traced

	 * and the tracer calls preempt_enable_notrace() causing

	 * an infinite recursion.

	 */

	preempt_disable_notrace();

	prev_ctx = exception_enter();

	preempt_enable_no_resched_notrace();



	preempt_schedule();



	preempt_disable_notrace();

	exception_exit(prev_ctx);

	preempt_enable_notrace();

}

EXPORT_SYMBOL_GPL(preempt_schedule_context);

#endif /* CONFIG_PREEMPT */



/**

 * context_tracking_user_exit - Inform the context tracking that the CPU is

 *                              exiting userspace mode and entering the kernel.

kernel/sched/core.c

+47 −0
Original line number Diff line number Diff line
@@ -2951,6 +2951,47 @@ asmlinkage __visible void __sched notrace preempt_schedule(void) 
}

NOKPROBE_SYMBOL(preempt_schedule);

EXPORT_SYMBOL(preempt_schedule);



#ifdef CONFIG_CONTEXT_TRACKING

/**

 * preempt_schedule_context - preempt_schedule called by tracing

 *

 * The tracing infrastructure uses preempt_enable_notrace to prevent

 * recursion and tracing preempt enabling caused by the tracing

 * infrastructure itself. But as tracing can happen in areas coming

 * from userspace or just about to enter userspace, a preempt enable

 * can occur before user_exit() is called. This will cause the scheduler

 * to be called when the system is still in usermode.

 *

 * To prevent this, the preempt_enable_notrace will use this function

 * instead of preempt_schedule() to exit user context if needed before

 * calling the scheduler.

 */

asmlinkage __visible void __sched notrace preempt_schedule_context(void)

{

	enum ctx_state prev_ctx;



	if (likely(!preemptible()))

		return;



	do {

		__preempt_count_add(PREEMPT_ACTIVE);

		/*

		 * Needs preempt disabled in case user_exit() is traced

		 * and the tracer calls preempt_enable_notrace() causing

		 * an infinite recursion.

		 */

		prev_ctx = exception_enter();

		__schedule();

		exception_exit(prev_ctx);



		__preempt_count_sub(PREEMPT_ACTIVE);

		barrier();

	} while (need_resched());

}

EXPORT_SYMBOL_GPL(preempt_schedule_context);

#endif /* CONFIG_CONTEXT_TRACKING */



#endif /* CONFIG_PREEMPT */



/*
@@ -7833,6 +7874,11 @@ static void cpu_cgroup_css_offline(struct cgroup_subsys_state *css) 
	sched_offline_group(tg);

}



static void cpu_cgroup_fork(struct task_struct *task)

{

	sched_move_task(task);

}



static int cpu_cgroup_can_attach(struct cgroup_subsys_state *css,

				 struct cgroup_taskset *tset)

{
@@ -8205,6 +8251,7 @@ struct cgroup_subsys cpu_cgrp_subsys = { 
	.css_free	= cpu_cgroup_css_free,

	.css_online	= cpu_cgroup_css_online,

	.css_offline	= cpu_cgroup_css_offline,

	.fork		= cpu_cgroup_fork,

	.can_attach	= cpu_cgroup_can_attach,

	.attach		= cpu_cgroup_attach,

	.exit		= cpu_cgroup_exit,

kernel/sched/deadline.c

+32 −9
Original line number Diff line number Diff line
@@ -518,12 +518,20 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer) 
	}



	/*

	 * We need to take care of a possible races here. In fact, the

	 * task might have changed its scheduling policy to something

	 * different from SCHED_DEADLINE or changed its reservation

	 * parameters (through sched_setattr()).

	 * We need to take care of several possible races here:

	 *

	 *   - the task might have changed its scheduling policy

	 *     to something different than SCHED_DEADLINE

	 *   - the task might have changed its reservation parameters

	 *     (through sched_setattr())

	 *   - the task might have been boosted by someone else and

	 *     might be in the boosting/deboosting path

	 *

	 * In all this cases we bail out, as the task is already

	 * in the runqueue or is going to be enqueued back anyway.

	 */

	if (!dl_task(p) || dl_se->dl_new)

	if (!dl_task(p) || dl_se->dl_new ||

	    dl_se->dl_boosted || !dl_se->dl_throttled)

		goto unlock;



	sched_clock_tick();
@@ -532,7 +540,7 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer) 
	dl_se->dl_yielded = 0;

	if (task_on_rq_queued(p)) {

		enqueue_task_dl(rq, p, ENQUEUE_REPLENISH);

		if (task_has_dl_policy(rq->curr))

		if (dl_task(rq->curr))

			check_preempt_curr_dl(rq, p, 0);

		else

			resched_curr(rq);
@@ -847,8 +855,19 @@ static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags) 
	 * smaller than our one... OTW we keep our runtime and

	 * deadline.

	 */

	if (pi_task && p->dl.dl_boosted && dl_prio(pi_task->normal_prio))

	if (pi_task && p->dl.dl_boosted && dl_prio(pi_task->normal_prio)) {

		pi_se = &pi_task->dl;

	} else if (!dl_prio(p->normal_prio)) {

		/*

		 * Special case in which we have a !SCHED_DEADLINE task

		 * that is going to be deboosted, but exceedes its

		 * runtime while doing so. No point in replenishing

		 * it, as it's going to return back to its original

		 * scheduling class after this.

		 */

		BUG_ON(!p->dl.dl_boosted || flags != ENQUEUE_REPLENISH);

		return;

	}



	/*

	 * If p is throttled, we do nothing. In fact, if it exhausted
@@ -1607,8 +1626,12 @@ static void switched_to_dl(struct rq *rq, struct task_struct *p) 
			/* Only reschedule if pushing failed */

			check_resched = 0;

#endif /* CONFIG_SMP */

		if (check_resched && task_has_dl_policy(rq->curr))

		if (check_resched) {

			if (dl_task(rq->curr))

				check_preempt_curr_dl(rq, p, 0);

			else

				resched_curr(rq);

		}

	}

}