Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
Merge tag 'timers-urgent-2021-03-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer fix from Thomas Gleixner:
"A single fix in for hrtimers to prevent an interrupt storm caused by
the lack of reevaluation of the timers which expire in softirq context
under certain circumstances, e.g. when the clock was set"
* tag 'timers-urgent-2021-03-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
hrtimer: Update softirq_expires_next correctly after __hrtimer_get_next_event()
+39
-21
+39
-21
kernel/time/hrtimer.c
+39
-21
kernel/time/hrtimer.c
···
546
546
}
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/*
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-
* Recomputes cpu_base::*next_timer and returns the earliest expires_next but
550
-
* does not set cpu_base::*expires_next, that is done by hrtimer_reprogram.
549
+
* Recomputes cpu_base::*next_timer and returns the earliest expires_next
550
+
* but does not set cpu_base::*expires_next, that is done by
551
+
* hrtimer[_force]_reprogram and hrtimer_interrupt only. When updating
552
+
* cpu_base::*expires_next right away, reprogramming logic would no longer
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+
* work.
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*
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* When a softirq is pending, we can ignore the HRTIMER_ACTIVE_SOFT bases,
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556
* those timers will get run whenever the softirq gets handled, at the end of
···
586
583
cpu_base->next_timer = next_timer;
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expires_next = __hrtimer_next_event_base(cpu_base, NULL, active,
588
585
expires_next);
586
+
}
587
+
588
+
return expires_next;
589
+
}
590
+
591
+
static ktime_t hrtimer_update_next_event(struct hrtimer_cpu_base *cpu_base)
592
+
{
593
+
ktime_t expires_next, soft = KTIME_MAX;
594
+
595
+
/*
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+
* If the soft interrupt has already been activated, ignore the
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+
* soft bases. They will be handled in the already raised soft
598
+
* interrupt.
599
+
*/
600
+
if (!cpu_base->softirq_activated) {
601
+
soft = __hrtimer_get_next_event(cpu_base, HRTIMER_ACTIVE_SOFT);
602
+
/*
603
+
* Update the soft expiry time. clock_settime() might have
604
+
* affected it.
605
+
*/
606
+
cpu_base->softirq_expires_next = soft;
607
+
}
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+
609
+
expires_next = __hrtimer_get_next_event(cpu_base, HRTIMER_ACTIVE_HARD);
610
+
/*
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+
* If a softirq timer is expiring first, update cpu_base->next_timer
612
+
* and program the hardware with the soft expiry time.
613
+
*/
614
+
if (expires_next > soft) {
615
+
cpu_base->next_timer = cpu_base->softirq_next_timer;
616
+
expires_next = soft;
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617
}
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618
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619
return expires_next;
···
662
628
{
663
629
ktime_t expires_next;
664
630
665
-
/*
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-
* Find the current next expiration time.
667
-
*/
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-
expires_next = __hrtimer_get_next_event(cpu_base, HRTIMER_ACTIVE_ALL);
669
-
670
-
if (cpu_base->next_timer && cpu_base->next_timer->is_soft) {
671
-
/*
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-
* When the softirq is activated, hrtimer has to be
673
-
* programmed with the first hard hrtimer because soft
674
-
* timer interrupt could occur too late.
675
-
*/
676
-
if (cpu_base->softirq_activated)
677
-
expires_next = __hrtimer_get_next_event(cpu_base,
678
-
HRTIMER_ACTIVE_HARD);
679
-
else
680
-
cpu_base->softirq_expires_next = expires_next;
681
-
}
631
+
expires_next = hrtimer_update_next_event(cpu_base);
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633
if (skip_equal && expires_next == cpu_base->expires_next)
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634
return;
···
1662
1644
1663
1645
__hrtimer_run_queues(cpu_base, now, flags, HRTIMER_ACTIVE_HARD);
1664
1646
1665
-
/* Reevaluate the clock bases for the next expiry */
1666
-
expires_next = __hrtimer_get_next_event(cpu_base, HRTIMER_ACTIVE_ALL);
1647
+
/* Reevaluate the clock bases for the [soft] next expiry */
1648
+
expires_next = hrtimer_update_next_event(cpu_base);
1667
1649
/*
1668
1650
* Store the new expiry value so the migration code can verify
1669
1651
* against it.