Commit 7f1e2ca9 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

hrtimer: fix rq->lock inversion (again) 



It appears I inadvertly introduced rq->lock recursion to the
hrtimer_start() path when I delegated running already expired
timers to softirq context.

This patch fixes it by introducing a __hrtimer_start_range_ns()
method that will not use raise_softirq_irqoff() but
__raise_softirq_irqoff() which avoids the wakeup.

It then also changes schedule() to check for pending softirqs and
do the wakeup then, I'm not quite sure I like this last bit, nor
am I convinced its really needed.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: paulus@samba.org
LKML-Reference: <20090313112301.096138802@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 7bee9463

include/linux/hrtimer.h

+5 −0
Original line number Diff line number Diff line
@@ -336,6 +336,11 @@ extern int hrtimer_start(struct hrtimer *timer, ktime_t tim, 
			 const enum hrtimer_mode mode);

extern int hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,

			unsigned long range_ns, const enum hrtimer_mode mode);

extern int

__hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,

			 unsigned long delta_ns,

			 const enum hrtimer_mode mode, int wakeup);



extern int hrtimer_cancel(struct hrtimer *timer);

extern int hrtimer_try_to_cancel(struct hrtimer *timer);

include/linux/interrupt.h

+1 −0
Original line number Diff line number Diff line
@@ -294,6 +294,7 @@ extern void softirq_init(void); 
#define __raise_softirq_irqoff(nr) do { or_softirq_pending(1UL << (nr)); } while (0)

extern void raise_softirq_irqoff(unsigned int nr);

extern void raise_softirq(unsigned int nr);

extern void wakeup_softirqd(void);



/* This is the worklist that queues up per-cpu softirq work.

 *

kernel/hrtimer.c

+34 −21
Original line number Diff line number Diff line
@@ -651,14 +651,20 @@ static inline void hrtimer_init_timer_hres(struct hrtimer *timer) 
 * and expiry check is done in the hrtimer_interrupt or in the softirq.

 */

static inline int hrtimer_enqueue_reprogram(struct hrtimer *timer,

					    struct hrtimer_clock_base *base)

					    struct hrtimer_clock_base *base,

					    int wakeup)

{

	if (base->cpu_base->hres_active && hrtimer_reprogram(timer, base)) {

		if (wakeup) {

			spin_unlock(&base->cpu_base->lock);

			raise_softirq_irqoff(HRTIMER_SOFTIRQ);

			spin_lock(&base->cpu_base->lock);

		} else

			__raise_softirq_irqoff(HRTIMER_SOFTIRQ);



		return 1;

	}



	return 0;

}
@@ -703,7 +709,8 @@ static inline int hrtimer_is_hres_enabled(void) { return 0; } 
static inline int hrtimer_switch_to_hres(void) { return 0; }

static inline void hrtimer_force_reprogram(struct hrtimer_cpu_base *base) { }

static inline int hrtimer_enqueue_reprogram(struct hrtimer *timer,

					    struct hrtimer_clock_base *base)

					    struct hrtimer_clock_base *base,

					    int wakeup)

{

	return 0;

}
@@ -886,20 +893,9 @@ remove_hrtimer(struct hrtimer *timer, struct hrtimer_clock_base *base) 
	return 0;

}



/**

 * hrtimer_start_range_ns - (re)start an hrtimer on the current CPU

 * @timer:	the timer to be added

 * @tim:	expiry time

 * @delta_ns:	"slack" range for the timer

 * @mode:	expiry mode: absolute (HRTIMER_ABS) or relative (HRTIMER_REL)

 *

 * Returns:

 *  0 on success

 *  1 when the timer was active

 */

int

hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim, unsigned long delta_ns,

			const enum hrtimer_mode mode)

int __hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,

		unsigned long delta_ns, const enum hrtimer_mode mode,

		int wakeup)

{

	struct hrtimer_clock_base *base, *new_base;

	unsigned long flags;
@@ -940,12 +936,29 @@ hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim, unsigned long delta_n 
	 * XXX send_remote_softirq() ?

	 */

	if (leftmost && new_base->cpu_base == &__get_cpu_var(hrtimer_bases))

		hrtimer_enqueue_reprogram(timer, new_base);

		hrtimer_enqueue_reprogram(timer, new_base, wakeup);



	unlock_hrtimer_base(timer, &flags);



	return ret;

}



/**

 * hrtimer_start_range_ns - (re)start an hrtimer on the current CPU

 * @timer:	the timer to be added

 * @tim:	expiry time

 * @delta_ns:	"slack" range for the timer

 * @mode:	expiry mode: absolute (HRTIMER_ABS) or relative (HRTIMER_REL)

 *

 * Returns:

 *  0 on success

 *  1 when the timer was active

 */

int hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,

		unsigned long delta_ns, const enum hrtimer_mode mode)

{

	return __hrtimer_start_range_ns(timer, tim, delta_ns, mode, 1);

}

EXPORT_SYMBOL_GPL(hrtimer_start_range_ns);



/**
@@ -961,7 +974,7 @@ EXPORT_SYMBOL_GPL(hrtimer_start_range_ns); 
int

hrtimer_start(struct hrtimer *timer, ktime_t tim, const enum hrtimer_mode mode)

{

	return hrtimer_start_range_ns(timer, tim, 0, mode);

	return __hrtimer_start_range_ns(timer, tim, 0, mode, 1);

}

EXPORT_SYMBOL_GPL(hrtimer_start);

kernel/sched.c

+11 −3
Original line number Diff line number Diff line
@@ -231,13 +231,20 @@ static void start_rt_bandwidth(struct rt_bandwidth *rt_b) 


	spin_lock(&rt_b->rt_runtime_lock);

	for (;;) {

		unsigned long delta;

		ktime_t soft, hard;



		if (hrtimer_active(&rt_b->rt_period_timer))

			break;



		now = hrtimer_cb_get_time(&rt_b->rt_period_timer);

		hrtimer_forward(&rt_b->rt_period_timer, now, rt_b->rt_period);

		hrtimer_start_expires(&rt_b->rt_period_timer,

				HRTIMER_MODE_ABS);



		soft = hrtimer_get_softexpires(&rt_b->rt_period_timer);

		hard = hrtimer_get_expires(&rt_b->rt_period_timer);

		delta = ktime_to_ns(ktime_sub(hard, soft));

		__hrtimer_start_range_ns(&rt_b->rt_period_timer, soft, delta,

				HRTIMER_MODE_ABS, 0);

	}

	spin_unlock(&rt_b->rt_runtime_lock);

}
@@ -1146,7 +1153,8 @@ static __init void init_hrtick(void) 
 */

static void hrtick_start(struct rq *rq, u64 delay)

{

	hrtimer_start(&rq->hrtick_timer, ns_to_ktime(delay), HRTIMER_MODE_REL);

	__hrtimer_start_range_ns(&rq->hrtick_timer, ns_to_ktime(delay), 0,

			HRTIMER_MODE_REL, 0);

}



static inline void init_hrtick(void)

kernel/softirq.c

+1 −1
Original line number Diff line number Diff line
@@ -58,7 +58,7 @@ static DEFINE_PER_CPU(struct task_struct *, ksoftirqd); 
 * to the pending events, so lets the scheduler to balance

 * the softirq load for us.

 */

static inline void wakeup_softirqd(void)

void wakeup_softirqd(void)

{

	/* Interrupts are disabled: no need to stop preemption */

	struct task_struct *tsk = __get_cpu_var(ksoftirqd);

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