Commit fb7b26e4 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 Thomas Gleixner:
 "This updates contains the following changes:

   - Fix a signal handling regression in the bit wait functions.

   - Avoid false positive warnings in the wakeup path.

   - Initialize the scheduler root domain properly.

   - Handle gtime calculations in proc/$PID/stat proper.

   - Add more documentation for the barriers in try_to_wake_up().

   - Fix a subtle race in try_to_wake_up() which might cause a task to
     be scheduled on two cpus

   - Compile static helper function only when it is used"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/core: Fix an SMP ordering race in try_to_wake_up() vs. schedule()
  sched/core: Better document the try_to_wake_up() barriers
  sched/cputime: Fix invalid gtime in proc
  sched/core: Clear the root_domain cpumasks in init_rootdomain()
  sched/core: Remove false-positive warning from wake_up_process()
  sched/wait: Fix signal handling in bit wait helpers
  sched/rt: Hide the push_irq_work_func() declaration
parents 69d2ca60 ecf7d01c

kernel/sched/core.c

+30 −6
Original line number Diff line number Diff line
@@ -1946,6 +1946,25 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) 
		goto stat;



#ifdef CONFIG_SMP

	/*

	 * Ensure we load p->on_cpu _after_ p->on_rq, otherwise it would be

	 * possible to, falsely, observe p->on_cpu == 0.

	 *

	 * One must be running (->on_cpu == 1) in order to remove oneself

	 * from the runqueue.

	 *

	 *  [S] ->on_cpu = 1;	[L] ->on_rq

	 *      UNLOCK rq->lock

	 *			RMB

	 *      LOCK   rq->lock

	 *  [S] ->on_rq = 0;    [L] ->on_cpu

	 *

	 * Pairs with the full barrier implied in the UNLOCK+LOCK on rq->lock

	 * from the consecutive calls to schedule(); the first switching to our

	 * task, the second putting it to sleep.

	 */

	smp_rmb();



	/*

	 * If the owning (remote) cpu is still in the middle of schedule() with

	 * this task as prev, wait until its done referencing the task.
@@ -1953,7 +1972,13 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) 
	while (p->on_cpu)

		cpu_relax();

	/*

	 * Pairs with the smp_wmb() in finish_lock_switch().

	 * Combined with the control dependency above, we have an effective

	 * smp_load_acquire() without the need for full barriers.

	 *

	 * Pairs with the smp_store_release() in finish_lock_switch().

	 *

	 * This ensures that tasks getting woken will be fully ordered against

	 * their previous state and preserve Program Order.

	 */

	smp_rmb();
@@ -2039,7 +2064,6 @@ out: 
 */

int wake_up_process(struct task_struct *p)

{

	WARN_ON(task_is_stopped_or_traced(p));

	return try_to_wake_up(p, TASK_NORMAL, 0);

}

EXPORT_SYMBOL(wake_up_process);
@@ -5847,13 +5871,13 @@ static int init_rootdomain(struct root_domain *rd) 
{

	memset(rd, 0, sizeof(*rd));



	if (!alloc_cpumask_var(&rd->span, GFP_KERNEL))

	if (!zalloc_cpumask_var(&rd->span, GFP_KERNEL))

		goto out;

	if (!alloc_cpumask_var(&rd->online, GFP_KERNEL))

	if (!zalloc_cpumask_var(&rd->online, GFP_KERNEL))

		goto free_span;

	if (!alloc_cpumask_var(&rd->dlo_mask, GFP_KERNEL))

	if (!zalloc_cpumask_var(&rd->dlo_mask, GFP_KERNEL))

		goto free_online;

	if (!alloc_cpumask_var(&rd->rto_mask, GFP_KERNEL))

	if (!zalloc_cpumask_var(&rd->rto_mask, GFP_KERNEL))

		goto free_dlo_mask;



	init_dl_bw(&rd->dl_bw);

kernel/sched/cputime.c

+3 −0
Original line number Diff line number Diff line
@@ -788,6 +788,9 @@ cputime_t task_gtime(struct task_struct *t) 
	unsigned int seq;

	cputime_t gtime;



	if (!context_tracking_is_enabled())

		return t->gtime;



	do {

		seq = read_seqbegin(&t->vtime_seqlock);

kernel/sched/rt.c

+1 −1
Original line number Diff line number Diff line
@@ -64,7 +64,7 @@ static void start_rt_bandwidth(struct rt_bandwidth *rt_b) 
	raw_spin_unlock(&rt_b->rt_runtime_lock);

}



#ifdef CONFIG_SMP

#if defined(CONFIG_SMP) && defined(HAVE_RT_PUSH_IPI)

static void push_irq_work_func(struct irq_work *work);

#endif

kernel/sched/sched.h

+3 −0
Original line number Diff line number Diff line
@@ -1073,6 +1073,9 @@ static inline void finish_lock_switch(struct rq *rq, struct task_struct *prev) 
	 * We must ensure this doesn't happen until the switch is completely

	 * finished.

	 *

	 * In particular, the load of prev->state in finish_task_switch() must

	 * happen before this.

	 *

	 * Pairs with the control dependency and rmb in try_to_wake_up().

	 */

	smp_store_release(&prev->on_cpu, 0);

kernel/sched/wait.c

+8 −8
Original line number Diff line number Diff line
@@ -583,18 +583,18 @@ EXPORT_SYMBOL(wake_up_atomic_t); 


__sched int bit_wait(struct wait_bit_key *word)

{

	if (signal_pending_state(current->state, current))

		return 1;

	schedule();

	if (signal_pending(current))

		return -EINTR;

	return 0;

}

EXPORT_SYMBOL(bit_wait);



__sched int bit_wait_io(struct wait_bit_key *word)

{

	if (signal_pending_state(current->state, current))

		return 1;

	io_schedule();

	if (signal_pending(current))

		return -EINTR;

	return 0;

}

EXPORT_SYMBOL(bit_wait_io);
@@ -602,11 +602,11 @@ EXPORT_SYMBOL(bit_wait_io); 
__sched int bit_wait_timeout(struct wait_bit_key *word)

{

	unsigned long now = READ_ONCE(jiffies);

	if (signal_pending_state(current->state, current))

		return 1;

	if (time_after_eq(now, word->timeout))

		return -EAGAIN;

	schedule_timeout(word->timeout - now);

	if (signal_pending(current))

		return -EINTR;

	return 0;

}

EXPORT_SYMBOL_GPL(bit_wait_timeout);
@@ -614,11 +614,11 @@ EXPORT_SYMBOL_GPL(bit_wait_timeout); 
__sched int bit_wait_io_timeout(struct wait_bit_key *word)

{

	unsigned long now = READ_ONCE(jiffies);

	if (signal_pending_state(current->state, current))

		return 1;

	if (time_after_eq(now, word->timeout))

		return -EAGAIN;

	io_schedule_timeout(word->timeout - now);

	if (signal_pending(current))

		return -EINTR;

	return 0;

}

EXPORT_SYMBOL_GPL(bit_wait_io_timeout);

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