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![Ulrich Obergfell](/assets/img/avatar_default.png)
Theoretically it is possible that the watchdog timer expires right at the time when a user sets 'watchdog_thresh' to zero (note: this disables the lockup detectors). In this scenario, the is_softlockup() function - which is called by the timer - could produce a false positive. Fix this by checking the current value of 'watchdog_thresh'. Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com> Acked-by: Don Zickus <dzickus@redhat.com> Reviewed-by: Aaron Tomlin <atomlin@redhat.com> Cc: Ulrich Obergfell <uobergfe@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1047 lines
29 KiB
C
1047 lines
29 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/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 <linux/tick.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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#include <linux/kthread.h>
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/*
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* The run state of the lockup detectors is controlled by the content of the
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* 'watchdog_enabled' variable. Each lockup detector has its dedicated bit -
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* bit 0 for the hard lockup detector and bit 1 for the soft lockup detector.
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*
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* 'watchdog_user_enabled', 'nmi_watchdog_enabled' and 'soft_watchdog_enabled'
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* are variables that are only used as an 'interface' between the parameters
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* in /proc/sys/kernel and the internal state bits in 'watchdog_enabled'. The
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* 'watchdog_thresh' variable is handled differently because its value is not
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* boolean, and the lockup detectors are 'suspended' while 'watchdog_thresh'
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* is equal zero.
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*/
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#define NMI_WATCHDOG_ENABLED_BIT 0
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#define SOFT_WATCHDOG_ENABLED_BIT 1
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#define NMI_WATCHDOG_ENABLED (1 << NMI_WATCHDOG_ENABLED_BIT)
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#define SOFT_WATCHDOG_ENABLED (1 << SOFT_WATCHDOG_ENABLED_BIT)
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static DEFINE_MUTEX(watchdog_proc_mutex);
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#ifdef CONFIG_HARDLOCKUP_DETECTOR
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static unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED|NMI_WATCHDOG_ENABLED;
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#else
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static unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED;
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#endif
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int __read_mostly nmi_watchdog_enabled;
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int __read_mostly soft_watchdog_enabled;
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int __read_mostly watchdog_user_enabled;
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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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int __read_mostly sysctl_hardlockup_all_cpu_backtrace;
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#else
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#define sysctl_softlockup_all_cpu_backtrace 0
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#define sysctl_hardlockup_all_cpu_backtrace 0
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#endif
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static struct cpumask watchdog_cpumask __read_mostly;
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unsigned long *watchdog_cpumask_bits = cpumask_bits(&watchdog_cpumask);
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/* Helper for online, unparked cpus. */
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#define for_each_watchdog_cpu(cpu) \
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for_each_cpu_and((cpu), cpu_online_mask, &watchdog_cpumask)
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/*
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* The 'watchdog_running' variable is set to 1 when the watchdog threads
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* are registered/started and is set to 0 when the watchdog threads are
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* unregistered/stopped, so it is an indicator whether the threads exist.
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*/
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static int __read_mostly watchdog_running;
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/*
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* If a subsystem has a need to deactivate the watchdog temporarily, it
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* can use the suspend/resume interface to achieve this. The content of
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* the 'watchdog_suspended' variable reflects this state. Existing threads
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* are parked/unparked by the lockup_detector_{suspend|resume} functions
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* (see comment blocks pertaining to those functions for further details).
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*
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* 'watchdog_suspended' also prevents threads from being registered/started
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* or unregistered/stopped via parameters in /proc/sys/kernel, so the state
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* of 'watchdog_running' cannot change while the watchdog is deactivated
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* temporarily (see related code in 'proc' handlers).
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*/
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static int __read_mostly watchdog_suspended;
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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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static DEFINE_PER_CPU(struct task_struct *, softlockup_task_ptr_saved);
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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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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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#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_enabled = 0;
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return 1;
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}
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__setup("nowatchdog", nowatchdog_setup);
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static int __init nosoftlockup_setup(char *str)
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{
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watchdog_enabled &= ~SOFT_WATCHDOG_ENABLED;
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return 1;
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}
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__setup("nosoftlockup", nosoftlockup_setup);
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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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static int __init hardlockup_all_cpu_backtrace_setup(char *str)
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{
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sysctl_hardlockup_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("hardlockup_all_cpu_backtrace=", hardlockup_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 running_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_watchdog_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_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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#endif
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void touch_softlockup_watchdog_sync(void)
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{
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__this_cpu_write(softlockup_touch_sync, true);
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__this_cpu_write(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 bool 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 true;
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__this_cpu_write(hrtimer_interrupts_saved, hrint);
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return false;
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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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if ((watchdog_enabled & SOFT_WATCHDOG_ENABLED) && watchdog_thresh){
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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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}
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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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struct pt_regs *regs = get_irq_regs();
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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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panic("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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#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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static int watchdog_enable_all_cpus(void);
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static void watchdog_disable_all_cpus(void);
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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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/*
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* When multiple processes are causing softlockups the
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* softlockup detector only warns on the first one
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* because the code relies on a full quiet cycle to
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* re-arm. The second process prevents the quiet cycle
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* and never gets reported. Use task pointers to detect
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* this.
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*/
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if (__this_cpu_read(softlockup_task_ptr_saved) !=
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current) {
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__this_cpu_write(soft_watchdog_warn, false);
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__touch_watchdog();
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}
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return HRTIMER_RESTART;
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}
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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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__this_cpu_write(softlockup_task_ptr_saved, 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);
|
|
if (softlockup_panic)
|
|
panic("softlockup: hung tasks");
|
|
__this_cpu_write(soft_watchdog_warn, true);
|
|
} else
|
|
__this_cpu_write(soft_watchdog_warn, false);
|
|
|
|
return HRTIMER_RESTART;
|
|
}
|
|
|
|
static void watchdog_set_prio(unsigned int policy, unsigned int prio)
|
|
{
|
|
struct sched_param param = { .sched_priority = prio };
|
|
|
|
sched_setscheduler(current, policy, ¶m);
|
|
}
|
|
|
|
static void watchdog_enable(unsigned int cpu)
|
|
{
|
|
struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer);
|
|
|
|
/* kick off the timer for the hardlockup detector */
|
|
hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
|
|
hrtimer->function = watchdog_timer_fn;
|
|
|
|
/* Enable the perf event */
|
|
watchdog_nmi_enable(cpu);
|
|
|
|
/* done here because hrtimer_start can only pin to smp_processor_id() */
|
|
hrtimer_start(hrtimer, ns_to_ktime(sample_period),
|
|
HRTIMER_MODE_REL_PINNED);
|
|
|
|
/* initialize timestamp */
|
|
watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1);
|
|
__touch_watchdog();
|
|
}
|
|
|
|
static void watchdog_disable(unsigned int cpu)
|
|
{
|
|
struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer);
|
|
|
|
watchdog_set_prio(SCHED_NORMAL, 0);
|
|
hrtimer_cancel(hrtimer);
|
|
/* disable the perf event */
|
|
watchdog_nmi_disable(cpu);
|
|
}
|
|
|
|
static void watchdog_cleanup(unsigned int cpu, bool online)
|
|
{
|
|
watchdog_disable(cpu);
|
|
}
|
|
|
|
static int watchdog_should_run(unsigned int cpu)
|
|
{
|
|
return __this_cpu_read(hrtimer_interrupts) !=
|
|
__this_cpu_read(soft_lockup_hrtimer_cnt);
|
|
}
|
|
|
|
/*
|
|
* The watchdog thread function - touches the timestamp.
|
|
*
|
|
* It only runs once every sample_period seconds (4 seconds by
|
|
* default) to reset the softlockup timestamp. If this gets delayed
|
|
* for more than 2*watchdog_thresh seconds then the debug-printout
|
|
* triggers in watchdog_timer_fn().
|
|
*/
|
|
static void watchdog(unsigned int cpu)
|
|
{
|
|
__this_cpu_write(soft_lockup_hrtimer_cnt,
|
|
__this_cpu_read(hrtimer_interrupts));
|
|
__touch_watchdog();
|
|
|
|
/*
|
|
* watchdog_nmi_enable() clears the NMI_WATCHDOG_ENABLED bit in the
|
|
* failure path. Check for failures that can occur asynchronously -
|
|
* for example, when CPUs are on-lined - and shut down the hardware
|
|
* perf event on each CPU accordingly.
|
|
*
|
|
* The only non-obvious place this bit can be cleared is through
|
|
* watchdog_nmi_enable(), so a pr_info() is placed there. Placing a
|
|
* pr_info here would be too noisy as it would result in a message
|
|
* every few seconds if the hardlockup was disabled but the softlockup
|
|
* enabled.
|
|
*/
|
|
if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
|
|
watchdog_nmi_disable(cpu);
|
|
}
|
|
|
|
#ifdef CONFIG_HARDLOCKUP_DETECTOR
|
|
/*
|
|
* People like the simple clean cpu node info on boot.
|
|
* Reduce the watchdog noise by only printing messages
|
|
* that are different from what cpu0 displayed.
|
|
*/
|
|
static unsigned long cpu0_err;
|
|
|
|
static int watchdog_nmi_enable(unsigned int cpu)
|
|
{
|
|
struct perf_event_attr *wd_attr;
|
|
struct perf_event *event = per_cpu(watchdog_ev, cpu);
|
|
|
|
/* nothing to do if the hard lockup detector is disabled */
|
|
if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
|
|
goto out;
|
|
|
|
/* is it already setup and enabled? */
|
|
if (event && event->state > PERF_EVENT_STATE_OFF)
|
|
goto out;
|
|
|
|
/* it is setup but not enabled */
|
|
if (event != NULL)
|
|
goto out_enable;
|
|
|
|
wd_attr = &wd_hw_attr;
|
|
wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
|
|
|
|
/* Try to register using hardware perf events */
|
|
event = perf_event_create_kernel_counter(wd_attr, cpu, NULL, watchdog_overflow_callback, NULL);
|
|
|
|
/* save cpu0 error for future comparision */
|
|
if (cpu == 0 && IS_ERR(event))
|
|
cpu0_err = PTR_ERR(event);
|
|
|
|
if (!IS_ERR(event)) {
|
|
/* only print for cpu0 or different than cpu0 */
|
|
if (cpu == 0 || cpu0_err)
|
|
pr_info("enabled on all CPUs, permanently consumes one hw-PMU counter.\n");
|
|
goto out_save;
|
|
}
|
|
|
|
/*
|
|
* Disable the hard lockup detector if _any_ CPU fails to set up
|
|
* set up the hardware perf event. The watchdog() function checks
|
|
* the NMI_WATCHDOG_ENABLED bit periodically.
|
|
*
|
|
* The barriers are for syncing up watchdog_enabled across all the
|
|
* cpus, as clear_bit() does not use barriers.
|
|
*/
|
|
smp_mb__before_atomic();
|
|
clear_bit(NMI_WATCHDOG_ENABLED_BIT, &watchdog_enabled);
|
|
smp_mb__after_atomic();
|
|
|
|
/* skip displaying the same error again */
|
|
if (cpu > 0 && (PTR_ERR(event) == cpu0_err))
|
|
return PTR_ERR(event);
|
|
|
|
/* vary the KERN level based on the returned errno */
|
|
if (PTR_ERR(event) == -EOPNOTSUPP)
|
|
pr_info("disabled (cpu%i): not supported (no LAPIC?)\n", cpu);
|
|
else if (PTR_ERR(event) == -ENOENT)
|
|
pr_warn("disabled (cpu%i): hardware events not enabled\n",
|
|
cpu);
|
|
else
|
|
pr_err("disabled (cpu%i): unable to create perf event: %ld\n",
|
|
cpu, PTR_ERR(event));
|
|
|
|
pr_info("Shutting down hard lockup detector on all cpus\n");
|
|
|
|
return PTR_ERR(event);
|
|
|
|
/* success path */
|
|
out_save:
|
|
per_cpu(watchdog_ev, cpu) = event;
|
|
out_enable:
|
|
perf_event_enable(per_cpu(watchdog_ev, cpu));
|
|
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);
|
|
}
|
|
if (cpu == 0) {
|
|
/* watchdog_nmi_enable() expects this to be zero initially. */
|
|
cpu0_err = 0;
|
|
}
|
|
}
|
|
|
|
#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,
|
|
};
|
|
|
|
/*
|
|
* park all watchdog threads that are specified in 'watchdog_cpumask'
|
|
*
|
|
* This function returns an error if kthread_park() of a watchdog thread
|
|
* fails. In this situation, the watchdog threads of some CPUs can already
|
|
* be parked and the watchdog threads of other CPUs can still be runnable.
|
|
* Callers are expected to handle this special condition as appropriate in
|
|
* their context.
|
|
*
|
|
* This function may only be called in a context that is protected against
|
|
* races with CPU hotplug - for example, via get_online_cpus().
|
|
*/
|
|
static int watchdog_park_threads(void)
|
|
{
|
|
int cpu, ret = 0;
|
|
|
|
for_each_watchdog_cpu(cpu) {
|
|
ret = kthread_park(per_cpu(softlockup_watchdog, cpu));
|
|
if (ret)
|
|
break;
|
|
}
|
|
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* unpark all watchdog threads that are specified in 'watchdog_cpumask'
|
|
*
|
|
* This function may only be called in a context that is protected against
|
|
* races with CPU hotplug - for example, via get_online_cpus().
|
|
*/
|
|
static void watchdog_unpark_threads(void)
|
|
{
|
|
int cpu;
|
|
|
|
for_each_watchdog_cpu(cpu)
|
|
kthread_unpark(per_cpu(softlockup_watchdog, cpu));
|
|
}
|
|
|
|
/*
|
|
* Suspend the hard and soft lockup detector by parking the watchdog threads.
|
|
*/
|
|
int lockup_detector_suspend(void)
|
|
{
|
|
int ret = 0;
|
|
|
|
get_online_cpus();
|
|
mutex_lock(&watchdog_proc_mutex);
|
|
/*
|
|
* Multiple suspend requests can be active in parallel (counted by
|
|
* the 'watchdog_suspended' variable). If the watchdog threads are
|
|
* running, the first caller takes care that they will be parked.
|
|
* The state of 'watchdog_running' cannot change while a suspend
|
|
* request is active (see related code in 'proc' handlers).
|
|
*/
|
|
if (watchdog_running && !watchdog_suspended)
|
|
ret = watchdog_park_threads();
|
|
|
|
if (ret == 0)
|
|
watchdog_suspended++;
|
|
else {
|
|
watchdog_disable_all_cpus();
|
|
pr_err("Failed to suspend lockup detectors, disabled\n");
|
|
watchdog_enabled = 0;
|
|
}
|
|
|
|
mutex_unlock(&watchdog_proc_mutex);
|
|
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Resume the hard and soft lockup detector by unparking the watchdog threads.
|
|
*/
|
|
void lockup_detector_resume(void)
|
|
{
|
|
mutex_lock(&watchdog_proc_mutex);
|
|
|
|
watchdog_suspended--;
|
|
/*
|
|
* The watchdog threads are unparked if they were previously running
|
|
* and if there is no more active suspend request.
|
|
*/
|
|
if (watchdog_running && !watchdog_suspended)
|
|
watchdog_unpark_threads();
|
|
|
|
mutex_unlock(&watchdog_proc_mutex);
|
|
put_online_cpus();
|
|
}
|
|
|
|
static int update_watchdog_all_cpus(void)
|
|
{
|
|
int ret;
|
|
|
|
ret = watchdog_park_threads();
|
|
if (ret)
|
|
return ret;
|
|
|
|
watchdog_unpark_threads();
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int watchdog_enable_all_cpus(void)
|
|
{
|
|
int err = 0;
|
|
|
|
if (!watchdog_running) {
|
|
err = smpboot_register_percpu_thread_cpumask(&watchdog_threads,
|
|
&watchdog_cpumask);
|
|
if (err)
|
|
pr_err("Failed to create watchdog threads, disabled\n");
|
|
else
|
|
watchdog_running = 1;
|
|
} else {
|
|
/*
|
|
* Enable/disable the lockup detectors or
|
|
* change the sample period 'on the fly'.
|
|
*/
|
|
err = update_watchdog_all_cpus();
|
|
|
|
if (err) {
|
|
watchdog_disable_all_cpus();
|
|
pr_err("Failed to update lockup detectors, disabled\n");
|
|
}
|
|
}
|
|
|
|
if (err)
|
|
watchdog_enabled = 0;
|
|
|
|
return err;
|
|
}
|
|
|
|
static void watchdog_disable_all_cpus(void)
|
|
{
|
|
if (watchdog_running) {
|
|
watchdog_running = 0;
|
|
smpboot_unregister_percpu_thread(&watchdog_threads);
|
|
}
|
|
}
|
|
|
|
#ifdef CONFIG_SYSCTL
|
|
|
|
/*
|
|
* Update the run state of the lockup detectors.
|
|
*/
|
|
static int proc_watchdog_update(void)
|
|
{
|
|
int err = 0;
|
|
|
|
/*
|
|
* Watchdog threads won't be started if they are already active.
|
|
* The 'watchdog_running' variable in watchdog_*_all_cpus() takes
|
|
* care of this. If those threads are already active, the sample
|
|
* period will be updated and the lockup detectors will be enabled
|
|
* or disabled 'on the fly'.
|
|
*/
|
|
if (watchdog_enabled && watchdog_thresh)
|
|
err = watchdog_enable_all_cpus();
|
|
else
|
|
watchdog_disable_all_cpus();
|
|
|
|
return err;
|
|
|
|
}
|
|
|
|
/*
|
|
* common function for watchdog, nmi_watchdog and soft_watchdog parameter
|
|
*
|
|
* caller | table->data points to | 'which' contains the flag(s)
|
|
* -------------------|-----------------------|-----------------------------
|
|
* proc_watchdog | watchdog_user_enabled | NMI_WATCHDOG_ENABLED or'ed
|
|
* | | with SOFT_WATCHDOG_ENABLED
|
|
* -------------------|-----------------------|-----------------------------
|
|
* proc_nmi_watchdog | nmi_watchdog_enabled | NMI_WATCHDOG_ENABLED
|
|
* -------------------|-----------------------|-----------------------------
|
|
* proc_soft_watchdog | soft_watchdog_enabled | SOFT_WATCHDOG_ENABLED
|
|
*/
|
|
static int proc_watchdog_common(int which, struct ctl_table *table, int write,
|
|
void __user *buffer, size_t *lenp, loff_t *ppos)
|
|
{
|
|
int err, old, new;
|
|
int *watchdog_param = (int *)table->data;
|
|
|
|
get_online_cpus();
|
|
mutex_lock(&watchdog_proc_mutex);
|
|
|
|
if (watchdog_suspended) {
|
|
/* no parameter changes allowed while watchdog is suspended */
|
|
err = -EAGAIN;
|
|
goto out;
|
|
}
|
|
|
|
/*
|
|
* If the parameter is being read return the state of the corresponding
|
|
* bit(s) in 'watchdog_enabled', else update 'watchdog_enabled' and the
|
|
* run state of the lockup detectors.
|
|
*/
|
|
if (!write) {
|
|
*watchdog_param = (watchdog_enabled & which) != 0;
|
|
err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
|
|
} else {
|
|
err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
|
|
if (err)
|
|
goto out;
|
|
|
|
/*
|
|
* There is a race window between fetching the current value
|
|
* from 'watchdog_enabled' and storing the new value. During
|
|
* this race window, watchdog_nmi_enable() can sneak in and
|
|
* clear the NMI_WATCHDOG_ENABLED bit in 'watchdog_enabled'.
|
|
* The 'cmpxchg' detects this race and the loop retries.
|
|
*/
|
|
do {
|
|
old = watchdog_enabled;
|
|
/*
|
|
* If the parameter value is not zero set the
|
|
* corresponding bit(s), else clear it(them).
|
|
*/
|
|
if (*watchdog_param)
|
|
new = old | which;
|
|
else
|
|
new = old & ~which;
|
|
} while (cmpxchg(&watchdog_enabled, old, new) != old);
|
|
|
|
/*
|
|
* Update the run state of the lockup detectors. There is _no_
|
|
* need to check the value returned by proc_watchdog_update()
|
|
* and to restore the previous value of 'watchdog_enabled' as
|
|
* both lockup detectors are disabled if proc_watchdog_update()
|
|
* returns an error.
|
|
*/
|
|
err = proc_watchdog_update();
|
|
}
|
|
out:
|
|
mutex_unlock(&watchdog_proc_mutex);
|
|
put_online_cpus();
|
|
return err;
|
|
}
|
|
|
|
/*
|
|
* /proc/sys/kernel/watchdog
|
|
*/
|
|
int proc_watchdog(struct ctl_table *table, int write,
|
|
void __user *buffer, size_t *lenp, loff_t *ppos)
|
|
{
|
|
return proc_watchdog_common(NMI_WATCHDOG_ENABLED|SOFT_WATCHDOG_ENABLED,
|
|
table, write, buffer, lenp, ppos);
|
|
}
|
|
|
|
/*
|
|
* /proc/sys/kernel/nmi_watchdog
|
|
*/
|
|
int proc_nmi_watchdog(struct ctl_table *table, int write,
|
|
void __user *buffer, size_t *lenp, loff_t *ppos)
|
|
{
|
|
return proc_watchdog_common(NMI_WATCHDOG_ENABLED,
|
|
table, write, buffer, lenp, ppos);
|
|
}
|
|
|
|
/*
|
|
* /proc/sys/kernel/soft_watchdog
|
|
*/
|
|
int proc_soft_watchdog(struct ctl_table *table, int write,
|
|
void __user *buffer, size_t *lenp, loff_t *ppos)
|
|
{
|
|
return proc_watchdog_common(SOFT_WATCHDOG_ENABLED,
|
|
table, write, buffer, lenp, ppos);
|
|
}
|
|
|
|
/*
|
|
* /proc/sys/kernel/watchdog_thresh
|
|
*/
|
|
int proc_watchdog_thresh(struct ctl_table *table, int write,
|
|
void __user *buffer, size_t *lenp, loff_t *ppos)
|
|
{
|
|
int err, old;
|
|
|
|
get_online_cpus();
|
|
mutex_lock(&watchdog_proc_mutex);
|
|
|
|
if (watchdog_suspended) {
|
|
/* no parameter changes allowed while watchdog is suspended */
|
|
err = -EAGAIN;
|
|
goto out;
|
|
}
|
|
|
|
old = ACCESS_ONCE(watchdog_thresh);
|
|
err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
|
|
|
|
if (err || !write)
|
|
goto out;
|
|
|
|
/*
|
|
* Update the sample period. Restore on failure.
|
|
*/
|
|
set_sample_period();
|
|
err = proc_watchdog_update();
|
|
if (err) {
|
|
watchdog_thresh = old;
|
|
set_sample_period();
|
|
}
|
|
out:
|
|
mutex_unlock(&watchdog_proc_mutex);
|
|
put_online_cpus();
|
|
return err;
|
|
}
|
|
|
|
/*
|
|
* The cpumask is the mask of possible cpus that the watchdog can run
|
|
* on, not the mask of cpus it is actually running on. This allows the
|
|
* user to specify a mask that will include cpus that have not yet
|
|
* been brought online, if desired.
|
|
*/
|
|
int proc_watchdog_cpumask(struct ctl_table *table, int write,
|
|
void __user *buffer, size_t *lenp, loff_t *ppos)
|
|
{
|
|
int err;
|
|
|
|
get_online_cpus();
|
|
mutex_lock(&watchdog_proc_mutex);
|
|
|
|
if (watchdog_suspended) {
|
|
/* no parameter changes allowed while watchdog is suspended */
|
|
err = -EAGAIN;
|
|
goto out;
|
|
}
|
|
|
|
err = proc_do_large_bitmap(table, write, buffer, lenp, ppos);
|
|
if (!err && write) {
|
|
/* Remove impossible cpus to keep sysctl output cleaner. */
|
|
cpumask_and(&watchdog_cpumask, &watchdog_cpumask,
|
|
cpu_possible_mask);
|
|
|
|
if (watchdog_running) {
|
|
/*
|
|
* Failure would be due to being unable to allocate
|
|
* a temporary cpumask, so we are likely not in a
|
|
* position to do much else to make things better.
|
|
*/
|
|
if (smpboot_update_cpumask_percpu_thread(
|
|
&watchdog_threads, &watchdog_cpumask) != 0)
|
|
pr_err("cpumask update failed\n");
|
|
}
|
|
}
|
|
out:
|
|
mutex_unlock(&watchdog_proc_mutex);
|
|
put_online_cpus();
|
|
return err;
|
|
}
|
|
|
|
#endif /* CONFIG_SYSCTL */
|
|
|
|
void __init lockup_detector_init(void)
|
|
{
|
|
set_sample_period();
|
|
|
|
#ifdef CONFIG_NO_HZ_FULL
|
|
if (tick_nohz_full_enabled()) {
|
|
pr_info("Disabling watchdog on nohz_full cores by default\n");
|
|
cpumask_copy(&watchdog_cpumask, housekeeping_mask);
|
|
} else
|
|
cpumask_copy(&watchdog_cpumask, cpu_possible_mask);
|
|
#else
|
|
cpumask_copy(&watchdog_cpumask, cpu_possible_mask);
|
|
#endif
|
|
|
|
if (watchdog_enabled)
|
|
watchdog_enable_all_cpus();
|
|
}
|