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Commit 14e07f02 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 fix from Thomas Gleixner:
 "A single fix for a cputime accounting regression which got introduced
  in the 4.11 cycle"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/cputime: Fix ksoftirqd cputime accounting regression
parents 8c9a694d 25e2d8c1

kernel/sched/cputime.c

+16 −11
Original line number Diff line number Diff line
@@ -34,6 +34,18 @@ void disable_sched_clock_irqtime(void) 
	sched_clock_irqtime = 0;

}



static void irqtime_account_delta(struct irqtime *irqtime, u64 delta,

				  enum cpu_usage_stat idx)

{

	u64 *cpustat = kcpustat_this_cpu->cpustat;



	u64_stats_update_begin(&irqtime->sync);

	cpustat[idx] += delta;

	irqtime->total += delta;

	irqtime->tick_delta += delta;

	u64_stats_update_end(&irqtime->sync);

}



/*

 * Called before incrementing preempt_count on {soft,}irq_enter

 * and before decrementing preempt_count on {soft,}irq_exit.
@@ -41,7 +53,6 @@ void disable_sched_clock_irqtime(void) 
void irqtime_account_irq(struct task_struct *curr)

{

	struct irqtime *irqtime = this_cpu_ptr(&cpu_irqtime);

	u64 *cpustat = kcpustat_this_cpu->cpustat;

	s64 delta;

	int cpu;
@@ -52,22 +63,16 @@ void irqtime_account_irq(struct task_struct *curr) 
	delta = sched_clock_cpu(cpu) - irqtime->irq_start_time;

	irqtime->irq_start_time += delta;



	u64_stats_update_begin(&irqtime->sync);

	/*

	 * We do not account for softirq time from ksoftirqd here.

	 * We want to continue accounting softirq time to ksoftirqd thread

	 * in that case, so as not to confuse scheduler with a special task

	 * that do not consume any time, but still wants to run.

	 */

	if (hardirq_count()) {

		cpustat[CPUTIME_IRQ] += delta;

		irqtime->tick_delta += delta;

	} else if (in_serving_softirq() && curr != this_cpu_ksoftirqd()) {

		cpustat[CPUTIME_SOFTIRQ] += delta;

		irqtime->tick_delta += delta;

	}



	u64_stats_update_end(&irqtime->sync);

	if (hardirq_count())

		irqtime_account_delta(irqtime, delta, CPUTIME_IRQ);

	else if (in_serving_softirq() && curr != this_cpu_ksoftirqd())

		irqtime_account_delta(irqtime, delta, CPUTIME_SOFTIRQ);

}

EXPORT_SYMBOL_GPL(irqtime_account_irq);

kernel/sched/sched.h

+7 −2
Original line number Diff line number Diff line
@@ -1869,6 +1869,7 @@ static inline void nohz_balance_exit_idle(unsigned int cpu) { } 


#ifdef CONFIG_IRQ_TIME_ACCOUNTING

struct irqtime {

	u64			total;

	u64			tick_delta;

	u64			irq_start_time;

	struct u64_stats_sync	sync;
@@ -1876,16 +1877,20 @@ struct irqtime { 


DECLARE_PER_CPU(struct irqtime, cpu_irqtime);



/*

 * Returns the irqtime minus the softirq time computed by ksoftirqd.

 * Otherwise ksoftirqd's sum_exec_runtime is substracted its own runtime

 * and never move forward.

 */

static inline u64 irq_time_read(int cpu)

{

	struct irqtime *irqtime = &per_cpu(cpu_irqtime, cpu);

	u64 *cpustat = kcpustat_cpu(cpu).cpustat;

	unsigned int seq;

	u64 total;



	do {

		seq = __u64_stats_fetch_begin(&irqtime->sync);

		total = cpustat[CPUTIME_SOFTIRQ] + cpustat[CPUTIME_IRQ];

		total = irqtime->total;

	} while (__u64_stats_fetch_retry(&irqtime->sync, seq));



	return total;