Attachment 1450216 Details for Bug 1569910 – skip expired timers on get_next_timer_interrupt() (V2)

[patch] skip expired timers on get_next_timer_interrupt() (V2)

01-skip-timers-on-get-next-timer-interrupt.patch (text/plain), 2.18 KB, created by Marcelo Tosatti on 2018-06-11 22:43:15 UTC

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Creator: Marcelo Tosatti

Created: 2018-06-11 22:43:15 UTC

Size: 2.18 KB

patch

obsolete

>diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
>index 6930619..17a09b8 100644
>--- a/include/linux/interrupt.h
>+++ b/include/linux/interrupt.h
>@@ -536,6 +536,11 @@ static inline void __raise_softirq_irqoff_ksoft(unsigned int nr)
> }
> #endif
> 
>+#ifdef CONFIG_PREEMPT_RT_FULL
>+#define TIMER_SOFTIRQS	((1 << TIMER_SOFTIRQ) | (1 << HRTIMER_SOFTIRQ))
>+DECLARE_PER_CPU(struct task_struct *, ktimer_softirqd);
>+#endif
>+
> extern void raise_softirq_irqoff(unsigned int nr);
> extern void raise_softirq(unsigned int nr);
> 
>diff --git a/kernel/softirq.c b/kernel/softirq.c
>index 3a53362..7f9b88b 100644
>--- a/kernel/softirq.c
>+++ b/kernel/softirq.c
>@@ -57,7 +57,6 @@ static struct softirq_action softirq_vec[NR_SOFTIRQS] __cacheline_aligned_in_smp
> 
> DEFINE_PER_CPU(struct task_struct *, ksoftirqd);
> #ifdef CONFIG_PREEMPT_RT_FULL
>-#define TIMER_SOFTIRQS	((1 << TIMER_SOFTIRQ) | (1 << HRTIMER_SOFTIRQ))
> DEFINE_PER_CPU(struct task_struct *, ktimer_softirqd);
> #endif
> 
>diff --git a/kernel/timer.c b/kernel/timer.c
>index dc85e24..1c0fe52 100644
>--- a/kernel/timer.c
>+++ b/kernel/timer.c
>@@ -1426,7 +1426,36 @@ u64 get_next_timer_interrupt(unsigned long basej, u64 basem)
> 			base->next_timer = __next_timer_interrupt(base);
> 		nextevt = base->next_timer;
> 		if (time_before_eq(nextevt, basej))
>+#ifdef CONFIG_PREEMPT_RT_FULL
>+		{
>+			unsigned int ir;
>+
>+			ir = __this_cpu_read(ktimer_softirqd)->softirqs_raised;
>+			ir &= TIMER_SOFTIRQS;
>+
>+			/* Pending timer softirq means expired timers
>+			 * will be executed either:
>+			 *       1) When ksoftirqd or ktimersoftd execute
>+			 *       2) On return from interrupt
>+			 *
>+			 * But with PREEMPT_RT_FULL, timer softirq processing
>+			 * is only performed on 1. Therefore its possible for
>+			 * an interrupt storm to occur never allowing
>+			 * ksoftirqd/ktimersoftd to execute, if expires < now.
>+			 * In that case, remove expired softirq timers
>+			 * from next timer interrupt calculation
>+			 * (since they will be processed by the pending
>+			 * TIMER_SOFTIRQ notification).
>+			 */
>+			if (ir != 0)
>+				expires = KTIME_MAX;
>+			else
>+				expires = basem;
>+		}
>+#else
>+
> 			expires = basem;
>+#endif
> 		else
> 			expires = basem + (nextevt - basej) * TICK_NSEC;
> 	}

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Attachments on bug 1569910: 1424448 | 1426103 | 1426617 | 1427282 | 1427947 | 1449271 | 1450216