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![Josh Hunt](/assets/img/avatar_default.png)
This taint flag will be set if the system has ever entered a softlockup state. Similar to TAINT_WARN it is useful to know whether or not the system has been in a softlockup state when debugging. [akpm@linux-foundation.org: apply the taint before calling panic()] Signed-off-by: Josh Hunt <johunt@akamai.com> Cc: Jason Baron <jbaron@akamai.com> Cc: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
651 lines
17 KiB
C
651 lines
17 KiB
C
/*
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* Detect hard and soft 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/mm.h>
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#include <linux/cpu.h>
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#include <linux/nmi.h>
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#include <linux/init.h>
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#include <linux/delay.h>
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#include <linux/freezer.h>
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#include <linux/kthread.h>
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#include <linux/lockdep.h>
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#include <linux/notifier.h>
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#include <linux/module.h>
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#include <linux/sysctl.h>
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#include <linux/smpboot.h>
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#include <linux/sched/rt.h>
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#include <asm/irq_regs.h>
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#include <linux/kvm_para.h>
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#include <linux/perf_event.h>
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int watchdog_user_enabled = 1;
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int __read_mostly watchdog_thresh = 10;
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#ifdef CONFIG_SMP
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int __read_mostly sysctl_softlockup_all_cpu_backtrace;
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#else
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#define sysctl_softlockup_all_cpu_backtrace 0
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#endif
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static int __read_mostly watchdog_running;
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static u64 __read_mostly sample_period;
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static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
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static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
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static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
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static DEFINE_PER_CPU(bool, softlockup_touch_sync);
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static DEFINE_PER_CPU(bool, soft_watchdog_warn);
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static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
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static DEFINE_PER_CPU(unsigned long, soft_lockup_hrtimer_cnt);
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#ifdef CONFIG_HARDLOCKUP_DETECTOR
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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(unsigned long, hrtimer_interrupts_saved);
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static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
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#endif
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static unsigned long soft_lockup_nmi_warn;
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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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#ifdef CONFIG_HARDLOCKUP_DETECTOR
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static int hardlockup_panic =
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CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
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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_user_enabled = 0;
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return 1;
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}
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__setup("nmi_watchdog=", hardlockup_panic_setup);
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#endif
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unsigned int __read_mostly softlockup_panic =
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CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC_VALUE;
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static int __init softlockup_panic_setup(char *str)
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{
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softlockup_panic = simple_strtoul(str, NULL, 0);
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return 1;
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}
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__setup("softlockup_panic=", softlockup_panic_setup);
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static int __init nowatchdog_setup(char *str)
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{
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watchdog_user_enabled = 0;
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return 1;
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}
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__setup("nowatchdog", nowatchdog_setup);
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/* deprecated */
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static int __init nosoftlockup_setup(char *str)
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{
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watchdog_user_enabled = 0;
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return 1;
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}
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__setup("nosoftlockup", nosoftlockup_setup);
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/* */
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#ifdef CONFIG_SMP
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static int __init softlockup_all_cpu_backtrace_setup(char *str)
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{
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sysctl_softlockup_all_cpu_backtrace =
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!!simple_strtol(str, NULL, 0);
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return 1;
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}
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__setup("softlockup_all_cpu_backtrace=", softlockup_all_cpu_backtrace_setup);
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#endif
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/*
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* Hard-lockup warnings should be triggered after just a few seconds. Soft-
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* lockups can have false positives under extreme conditions. So we generally
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* want a higher threshold for soft lockups than for hard lockups. So we couple
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* the thresholds with a factor: we make the soft threshold twice the amount of
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* time the hard threshold is.
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*/
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static int get_softlockup_thresh(void)
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{
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return watchdog_thresh * 2;
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}
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/*
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* Returns seconds, approximately. We don't need nanosecond
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* resolution, and we don't need to waste time with a big divide when
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* 2^30ns == 1.074s.
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*/
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static unsigned long get_timestamp(void)
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{
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return local_clock() >> 30LL; /* 2^30 ~= 10^9 */
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}
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static void set_sample_period(void)
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{
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/*
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* convert watchdog_thresh from seconds to ns
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* the divide by 5 is to give hrtimer several chances (two
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* or three with the current relation between the soft
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* and hard thresholds) to increment before the
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* hardlockup detector generates a warning
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*/
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sample_period = get_softlockup_thresh() * ((u64)NSEC_PER_SEC / 5);
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}
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/* Commands for resetting the watchdog */
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static void __touch_watchdog(void)
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{
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__this_cpu_write(watchdog_touch_ts, get_timestamp());
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}
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void touch_softlockup_watchdog(void)
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{
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/*
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* Preemption can be enabled. It doesn't matter which CPU's timestamp
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* gets zeroed here, so use the raw_ operation.
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*/
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raw_cpu_write(watchdog_touch_ts, 0);
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}
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EXPORT_SYMBOL(touch_softlockup_watchdog);
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void touch_all_softlockup_watchdogs(void)
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{
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int cpu;
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/*
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* this is done lockless
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* do we care if a 0 races with a timestamp?
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* all it means is the softlock check starts one cycle later
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*/
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for_each_online_cpu(cpu)
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per_cpu(watchdog_touch_ts, cpu) = 0;
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}
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#ifdef CONFIG_HARDLOCKUP_DETECTOR
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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_get_cpu_var(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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#endif
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void touch_softlockup_watchdog_sync(void)
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{
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__raw_get_cpu_var(softlockup_touch_sync) = true;
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__raw_get_cpu_var(watchdog_touch_ts) = 0;
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}
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#ifdef CONFIG_HARDLOCKUP_DETECTOR
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/* watchdog detector functions */
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static int is_hardlockup(void)
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{
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unsigned long hrint = __this_cpu_read(hrtimer_interrupts);
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if (__this_cpu_read(hrtimer_interrupts_saved) == hrint)
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return 1;
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__this_cpu_write(hrtimer_interrupts_saved, hrint);
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return 0;
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}
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#endif
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static int is_softlockup(unsigned long touch_ts)
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{
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unsigned long now = get_timestamp();
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/* Warn about unreasonable delays: */
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if (time_after(now, touch_ts + get_softlockup_thresh()))
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return now - touch_ts;
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return 0;
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}
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#ifdef CONFIG_HARDLOCKUP_DETECTOR
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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 (__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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if (hardlockup_panic)
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panic("Watchdog detected hard LOCKUP on cpu %d",
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this_cpu);
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else
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WARN(1, "Watchdog detected hard LOCKUP on cpu %d",
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this_cpu);
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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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#endif /* CONFIG_HARDLOCKUP_DETECTOR */
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static void watchdog_interrupt_count(void)
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{
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__this_cpu_inc(hrtimer_interrupts);
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}
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static int watchdog_nmi_enable(unsigned int cpu);
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static void watchdog_nmi_disable(unsigned int cpu);
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/* watchdog kicker functions */
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static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
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{
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unsigned long touch_ts = __this_cpu_read(watchdog_touch_ts);
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struct pt_regs *regs = get_irq_regs();
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int duration;
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int softlockup_all_cpu_backtrace = sysctl_softlockup_all_cpu_backtrace;
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/* kick the hardlockup detector */
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watchdog_interrupt_count();
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/* kick the softlockup detector */
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wake_up_process(__this_cpu_read(softlockup_watchdog));
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/* .. and repeat */
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hrtimer_forward_now(hrtimer, ns_to_ktime(sample_period));
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if (touch_ts == 0) {
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if (unlikely(__this_cpu_read(softlockup_touch_sync))) {
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/*
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* If the time stamp was touched atomically
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* make sure the scheduler tick is up to date.
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*/
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__this_cpu_write(softlockup_touch_sync, false);
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sched_clock_tick();
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}
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/* Clear the guest paused flag on watchdog reset */
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kvm_check_and_clear_guest_paused();
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__touch_watchdog();
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return HRTIMER_RESTART;
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}
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/* check for a softlockup
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* This is done by making sure a high priority task is
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* being scheduled. The task touches the watchdog to
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* indicate it is getting cpu time. If it hasn't then
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* this is a good indication some task is hogging the cpu
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*/
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duration = is_softlockup(touch_ts);
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if (unlikely(duration)) {
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/*
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* If a virtual machine is stopped by the host it can look to
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* the watchdog like a soft lockup, check to see if the host
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* stopped the vm before we issue the warning
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*/
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if (kvm_check_and_clear_guest_paused())
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return HRTIMER_RESTART;
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/* only warn once */
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if (__this_cpu_read(soft_watchdog_warn) == true)
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return HRTIMER_RESTART;
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if (softlockup_all_cpu_backtrace) {
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/* Prevent multiple soft-lockup reports if one cpu is already
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* engaged in dumping cpu back traces
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*/
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if (test_and_set_bit(0, &soft_lockup_nmi_warn)) {
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/* Someone else will report us. Let's give up */
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__this_cpu_write(soft_watchdog_warn, true);
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return HRTIMER_RESTART;
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}
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}
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pr_emerg("BUG: soft lockup - CPU#%d stuck for %us! [%s:%d]\n",
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smp_processor_id(), duration,
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current->comm, task_pid_nr(current));
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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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if (softlockup_all_cpu_backtrace) {
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/* Avoid generating two back traces for current
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* given that one is already made above
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*/
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trigger_allbutself_cpu_backtrace();
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clear_bit(0, &soft_lockup_nmi_warn);
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/* Barrier to sync with other cpus */
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smp_mb__after_atomic();
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}
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add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
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if (softlockup_panic)
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panic("softlockup: hung tasks");
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__this_cpu_write(soft_watchdog_warn, true);
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} else
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__this_cpu_write(soft_watchdog_warn, false);
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return HRTIMER_RESTART;
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}
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static void watchdog_set_prio(unsigned int policy, unsigned int prio)
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{
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struct sched_param param = { .sched_priority = prio };
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sched_setscheduler(current, policy, ¶m);
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}
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static void watchdog_enable(unsigned int cpu)
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{
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struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
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/* kick off the timer for the hardlockup detector */
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hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
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hrtimer->function = watchdog_timer_fn;
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/* Enable the perf event */
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watchdog_nmi_enable(cpu);
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/* done here because hrtimer_start can only pin to smp_processor_id() */
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hrtimer_start(hrtimer, ns_to_ktime(sample_period),
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HRTIMER_MODE_REL_PINNED);
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/* initialize timestamp */
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watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1);
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__touch_watchdog();
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}
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static void watchdog_disable(unsigned int cpu)
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{
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struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
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watchdog_set_prio(SCHED_NORMAL, 0);
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hrtimer_cancel(hrtimer);
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/* disable the perf event */
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watchdog_nmi_disable(cpu);
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}
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static void watchdog_cleanup(unsigned int cpu, bool online)
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{
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watchdog_disable(cpu);
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}
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static int watchdog_should_run(unsigned int cpu)
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{
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return __this_cpu_read(hrtimer_interrupts) !=
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__this_cpu_read(soft_lockup_hrtimer_cnt);
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}
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/*
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* The watchdog thread function - touches the timestamp.
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*
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* It only runs once every sample_period seconds (4 seconds by
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* default) to reset the softlockup timestamp. If this gets delayed
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* for more than 2*watchdog_thresh seconds then the debug-printout
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* triggers in watchdog_timer_fn().
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*/
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static void watchdog(unsigned int cpu)
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{
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__this_cpu_write(soft_lockup_hrtimer_cnt,
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__this_cpu_read(hrtimer_interrupts));
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__touch_watchdog();
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}
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#ifdef CONFIG_HARDLOCKUP_DETECTOR
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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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static 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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/* 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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/* 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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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:
|
|
return 0;
|
|
}
|
|
|
|
static void watchdog_nmi_disable(unsigned int cpu)
|
|
{
|
|
struct perf_event *event = per_cpu(watchdog_ev, cpu);
|
|
|
|
if (event) {
|
|
perf_event_disable(event);
|
|
per_cpu(watchdog_ev, cpu) = NULL;
|
|
|
|
/* should be in cleanup, but blocks oprofile */
|
|
perf_event_release_kernel(event);
|
|
}
|
|
return;
|
|
}
|
|
#else
|
|
static int watchdog_nmi_enable(unsigned int cpu) { return 0; }
|
|
static void watchdog_nmi_disable(unsigned int cpu) { return; }
|
|
#endif /* CONFIG_HARDLOCKUP_DETECTOR */
|
|
|
|
static struct smp_hotplug_thread watchdog_threads = {
|
|
.store = &softlockup_watchdog,
|
|
.thread_should_run = watchdog_should_run,
|
|
.thread_fn = watchdog,
|
|
.thread_comm = "watchdog/%u",
|
|
.setup = watchdog_enable,
|
|
.cleanup = watchdog_cleanup,
|
|
.park = watchdog_disable,
|
|
.unpark = watchdog_enable,
|
|
};
|
|
|
|
static void restart_watchdog_hrtimer(void *info)
|
|
{
|
|
struct hrtimer *hrtimer = &__raw_get_cpu_var(watchdog_hrtimer);
|
|
int ret;
|
|
|
|
/*
|
|
* No need to cancel and restart hrtimer if it is currently executing
|
|
* because it will reprogram itself with the new period now.
|
|
* We should never see it unqueued here because we are running per-cpu
|
|
* with interrupts disabled.
|
|
*/
|
|
ret = hrtimer_try_to_cancel(hrtimer);
|
|
if (ret == 1)
|
|
hrtimer_start(hrtimer, ns_to_ktime(sample_period),
|
|
HRTIMER_MODE_REL_PINNED);
|
|
}
|
|
|
|
static void update_timers(int cpu)
|
|
{
|
|
/*
|
|
* Make sure that perf event counter will adopt to a new
|
|
* sampling period. Updating the sampling period directly would
|
|
* be much nicer but we do not have an API for that now so
|
|
* let's use a big hammer.
|
|
* Hrtimer will adopt the new period on the next tick but this
|
|
* might be late already so we have to restart the timer as well.
|
|
*/
|
|
watchdog_nmi_disable(cpu);
|
|
smp_call_function_single(cpu, restart_watchdog_hrtimer, NULL, 1);
|
|
watchdog_nmi_enable(cpu);
|
|
}
|
|
|
|
static void update_timers_all_cpus(void)
|
|
{
|
|
int cpu;
|
|
|
|
get_online_cpus();
|
|
for_each_online_cpu(cpu)
|
|
update_timers(cpu);
|
|
put_online_cpus();
|
|
}
|
|
|
|
static int watchdog_enable_all_cpus(bool sample_period_changed)
|
|
{
|
|
int err = 0;
|
|
|
|
if (!watchdog_running) {
|
|
err = smpboot_register_percpu_thread(&watchdog_threads);
|
|
if (err)
|
|
pr_err("Failed to create watchdog threads, disabled\n");
|
|
else
|
|
watchdog_running = 1;
|
|
} else if (sample_period_changed) {
|
|
update_timers_all_cpus();
|
|
}
|
|
|
|
return err;
|
|
}
|
|
|
|
/* prepare/enable/disable routines */
|
|
/* sysctl functions */
|
|
#ifdef CONFIG_SYSCTL
|
|
static void watchdog_disable_all_cpus(void)
|
|
{
|
|
if (watchdog_running) {
|
|
watchdog_running = 0;
|
|
smpboot_unregister_percpu_thread(&watchdog_threads);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* proc handler for /proc/sys/kernel/nmi_watchdog,watchdog_thresh
|
|
*/
|
|
|
|
int proc_dowatchdog(struct ctl_table *table, int write,
|
|
void __user *buffer, size_t *lenp, loff_t *ppos)
|
|
{
|
|
int err, old_thresh, old_enabled;
|
|
static DEFINE_MUTEX(watchdog_proc_mutex);
|
|
|
|
mutex_lock(&watchdog_proc_mutex);
|
|
old_thresh = ACCESS_ONCE(watchdog_thresh);
|
|
old_enabled = ACCESS_ONCE(watchdog_user_enabled);
|
|
|
|
err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
|
|
if (err || !write)
|
|
goto out;
|
|
|
|
set_sample_period();
|
|
/*
|
|
* Watchdog threads shouldn't be enabled if they are
|
|
* disabled. The 'watchdog_running' variable check in
|
|
* watchdog_*_all_cpus() function takes care of this.
|
|
*/
|
|
if (watchdog_user_enabled && watchdog_thresh)
|
|
err = watchdog_enable_all_cpus(old_thresh != watchdog_thresh);
|
|
else
|
|
watchdog_disable_all_cpus();
|
|
|
|
/* Restore old values on failure */
|
|
if (err) {
|
|
watchdog_thresh = old_thresh;
|
|
watchdog_user_enabled = old_enabled;
|
|
}
|
|
out:
|
|
mutex_unlock(&watchdog_proc_mutex);
|
|
return err;
|
|
}
|
|
#endif /* CONFIG_SYSCTL */
|
|
|
|
void __init lockup_detector_init(void)
|
|
{
|
|
set_sample_period();
|
|
|
|
if (watchdog_user_enabled)
|
|
watchdog_enable_all_cpus(false);
|
|
}
|