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f49a4af3fa
The dedicated helper is more verbose and efficient comparing to cpumask_next() followed by cpumask_first(). Signed-off-by: "Yury Norov [NVIDIA]" <yury.norov@gmail.com> Reviewed-by: Douglas Anderson <dianders@chromium.org>
110 lines
3 KiB
C
110 lines
3 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/cpu.h>
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#include <linux/cpumask.h>
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#include <linux/kernel.h>
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#include <linux/nmi.h>
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#include <linux/percpu-defs.h>
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static cpumask_t __read_mostly watchdog_cpus;
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static unsigned int watchdog_next_cpu(unsigned int cpu)
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{
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unsigned int next_cpu;
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next_cpu = cpumask_next_wrap(cpu, &watchdog_cpus);
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if (next_cpu == cpu)
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return nr_cpu_ids;
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return next_cpu;
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}
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int __init watchdog_hardlockup_probe(void)
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{
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return 0;
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}
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void watchdog_hardlockup_enable(unsigned int cpu)
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{
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unsigned int next_cpu;
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/*
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* The new CPU will be marked online before the hrtimer interrupt
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* gets a chance to run on it. If another CPU tests for a
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* hardlockup on the new CPU before it has run its the hrtimer
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* interrupt, it will get a false positive. Touch the watchdog on
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* the new CPU to delay the check for at least 3 sampling periods
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* to guarantee one hrtimer has run on the new CPU.
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*/
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watchdog_hardlockup_touch_cpu(cpu);
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/*
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* We are going to check the next CPU. Our watchdog_hrtimer
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* need not be zero if the CPU has already been online earlier.
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* Touch the watchdog on the next CPU to avoid false positive
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* if we try to check it in less then 3 interrupts.
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*/
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next_cpu = watchdog_next_cpu(cpu);
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if (next_cpu < nr_cpu_ids)
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watchdog_hardlockup_touch_cpu(next_cpu);
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/*
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* Makes sure that watchdog is touched on this CPU before
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* other CPUs could see it in watchdog_cpus. The counter
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* part is in watchdog_buddy_check_hardlockup().
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*/
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smp_wmb();
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cpumask_set_cpu(cpu, &watchdog_cpus);
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}
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void watchdog_hardlockup_disable(unsigned int cpu)
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{
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unsigned int next_cpu = watchdog_next_cpu(cpu);
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/*
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* Offlining this CPU will cause the CPU before this one to start
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* checking the one after this one. If this CPU just finished checking
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* the next CPU and updating hrtimer_interrupts_saved, and then the
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* previous CPU checks it within one sample period, it will trigger a
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* false positive. Touch the watchdog on the next CPU to prevent it.
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*/
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if (next_cpu < nr_cpu_ids)
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watchdog_hardlockup_touch_cpu(next_cpu);
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/*
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* Makes sure that watchdog is touched on the next CPU before
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* this CPU disappear in watchdog_cpus. The counter part is in
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* watchdog_buddy_check_hardlockup().
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*/
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smp_wmb();
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cpumask_clear_cpu(cpu, &watchdog_cpus);
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}
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void watchdog_buddy_check_hardlockup(int hrtimer_interrupts)
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{
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unsigned int next_cpu;
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/*
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* Test for hardlockups every 3 samples. The sample period is
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* watchdog_thresh * 2 / 5, so 3 samples gets us back to slightly over
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* watchdog_thresh (over by 20%).
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*/
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if (hrtimer_interrupts % 3 != 0)
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return;
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/* check for a hardlockup on the next CPU */
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next_cpu = watchdog_next_cpu(smp_processor_id());
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if (next_cpu >= nr_cpu_ids)
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return;
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/*
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* Make sure that the watchdog was touched on next CPU when
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* watchdog_next_cpu() returned another one because of
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* a change in watchdog_hardlockup_enable()/disable().
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*/
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smp_rmb();
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watchdog_hardlockup_check(next_cpu, NULL);
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}
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