231 lines
6.3 KiB
C
231 lines
6.3 KiB
C
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/*
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* Detect hard lockups on a system
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*
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* started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
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*
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* Note: Most of this code is borrowed heavily from the original softlockup
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* detector, so thanks to Ingo for the initial implementation.
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* Some chunks also taken from the old x86-specific nmi watchdog code, thanks
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* to those contributors as well.
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*/
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#define pr_fmt(fmt) "NMI watchdog: " fmt
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#include <linux/nmi.h>
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#include <linux/module.h>
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#include <asm/irq_regs.h>
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#include <linux/perf_event.h>
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static DEFINE_PER_CPU(bool, hard_watchdog_warn);
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static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
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static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
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/* boot commands */
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/*
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* Should we panic when a soft-lockup or hard-lockup occurs:
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*/
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unsigned int __read_mostly hardlockup_panic =
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CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
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static unsigned long hardlockup_allcpu_dumped;
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/*
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* We may not want to enable hard lockup detection by default in all cases,
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* for example when running the kernel as a guest on a hypervisor. In these
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* cases this function can be called to disable hard lockup detection. This
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* function should only be executed once by the boot processor before the
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* kernel command line parameters are parsed, because otherwise it is not
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* possible to override this in hardlockup_panic_setup().
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*/
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void hardlockup_detector_disable(void)
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{
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watchdog_enabled &= ~NMI_WATCHDOG_ENABLED;
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}
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static int __init hardlockup_panic_setup(char *str)
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{
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if (!strncmp(str, "panic", 5))
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hardlockup_panic = 1;
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else if (!strncmp(str, "nopanic", 7))
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hardlockup_panic = 0;
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else if (!strncmp(str, "0", 1))
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watchdog_enabled &= ~NMI_WATCHDOG_ENABLED;
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else if (!strncmp(str, "1", 1))
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watchdog_enabled |= NMI_WATCHDOG_ENABLED;
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return 1;
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}
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__setup("nmi_watchdog=", hardlockup_panic_setup);
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void touch_nmi_watchdog(void)
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{
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/*
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* Using __raw here because some code paths have
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* preemption enabled. If preemption is enabled
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* then interrupts should be enabled too, in which
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* case we shouldn't have to worry about the watchdog
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* going off.
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*/
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raw_cpu_write(watchdog_nmi_touch, true);
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touch_softlockup_watchdog();
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}
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EXPORT_SYMBOL(touch_nmi_watchdog);
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static struct perf_event_attr wd_hw_attr = {
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.type = PERF_TYPE_HARDWARE,
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.config = PERF_COUNT_HW_CPU_CYCLES,
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.size = sizeof(struct perf_event_attr),
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.pinned = 1,
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.disabled = 1,
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};
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/* Callback function for perf event subsystem */
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static void watchdog_overflow_callback(struct perf_event *event,
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struct perf_sample_data *data,
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struct pt_regs *regs)
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{
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/* Ensure the watchdog never gets throttled */
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event->hw.interrupts = 0;
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if (atomic_read(&watchdog_park_in_progress) != 0)
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return;
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if (__this_cpu_read(watchdog_nmi_touch) == true) {
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__this_cpu_write(watchdog_nmi_touch, false);
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return;
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}
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/* check for a hardlockup
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* This is done by making sure our timer interrupt
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* is incrementing. The timer interrupt should have
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* fired multiple times before we overflow'd. If it hasn't
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* then this is a good indication the cpu is stuck
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*/
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if (is_hardlockup()) {
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int this_cpu = smp_processor_id();
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/* only print hardlockups once */
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if (__this_cpu_read(hard_watchdog_warn) == true)
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return;
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pr_emerg("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
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print_modules();
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print_irqtrace_events(current);
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if (regs)
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show_regs(regs);
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else
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dump_stack();
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/*
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* Perform all-CPU dump only once to avoid multiple hardlockups
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* generating interleaving traces
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*/
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if (sysctl_hardlockup_all_cpu_backtrace &&
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!test_and_set_bit(0, &hardlockup_allcpu_dumped))
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trigger_allbutself_cpu_backtrace();
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if (hardlockup_panic)
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nmi_panic(regs, "Hard LOCKUP");
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__this_cpu_write(hard_watchdog_warn, true);
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return;
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}
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__this_cpu_write(hard_watchdog_warn, false);
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return;
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}
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/*
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* People like the simple clean cpu node info on boot.
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* Reduce the watchdog noise by only printing messages
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* that are different from what cpu0 displayed.
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*/
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static unsigned long cpu0_err;
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int watchdog_nmi_enable(unsigned int cpu)
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{
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struct perf_event_attr *wd_attr;
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struct perf_event *event = per_cpu(watchdog_ev, cpu);
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/* nothing to do if the hard lockup detector is disabled */
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if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
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goto out;
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/* is it already setup and enabled? */
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if (event && event->state > PERF_EVENT_STATE_OFF)
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goto out;
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/* it is setup but not enabled */
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if (event != NULL)
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goto out_enable;
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wd_attr = &wd_hw_attr;
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wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
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/* Try to register using hardware perf events */
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event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL);
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/* save cpu0 error for future comparision */
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if (cpu == 0 && IS_ERR(event))
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cpu0_err = PTR_ERR(event);
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if (!IS_ERR(event)) {
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/* only print for cpu0 or different than cpu0 */
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if (cpu == 0 || cpu0_err)
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pr_info("enabled on all CPUs, permanently consumes one hw-PMU counter.\n");
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goto out_save;
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}
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/*
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* Disable the hard lockup detector if _any_ CPU fails to set up
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* set up the hardware perf event. The watchdog() function checks
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* the NMI_WATCHDOG_ENABLED bit periodically.
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*
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* The barriers are for syncing up watchdog_enabled across all the
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* cpus, as clear_bit() does not use barriers.
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*/
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smp_mb__before_atomic();
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clear_bit(NMI_WATCHDOG_ENABLED_BIT, &watchdog_enabled);
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smp_mb__after_atomic();
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/* skip displaying the same error again */
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if (cpu > 0 && (PTR_ERR(event) == cpu0_err))
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return PTR_ERR(event);
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/* vary the KERN level based on the returned errno */
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if (PTR_ERR(event) == -EOPNOTSUPP)
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pr_info("disabled (cpu%i): not supported (no LAPIC?)\n", cpu);
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else if (PTR_ERR(event) == -ENOENT)
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pr_warn("disabled (cpu%i): hardware events not enabled\n",
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cpu);
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else
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pr_err("disabled (cpu%i): unable to create perf event: %ld\n",
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cpu, PTR_ERR(event));
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pr_info("Shutting down hard lockup detector on all cpus\n");
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return PTR_ERR(event);
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/* success path */
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out_save:
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per_cpu(watchdog_ev, cpu) = event;
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out_enable:
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perf_event_enable(per_cpu(watchdog_ev, cpu));
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out:
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return 0;
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}
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void watchdog_nmi_disable(unsigned int cpu)
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{
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struct perf_event *event = per_cpu(watchdog_ev, cpu);
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if (event) {
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perf_event_disable(event);
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per_cpu(watchdog_ev, cpu) = NULL;
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/* should be in cleanup, but blocks oprofile */
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perf_event_release_kernel(event);
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}
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if (cpu == 0) {
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/* watchdog_nmi_enable() expects this to be zero initially. */
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cpu0_err = 0;
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}
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}
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