diff options
| -rw-r--r-- | Documentation/kernel-parameters.txt | 6 | ||||
| -rw-r--r-- | Documentation/sysctl/kernel.txt | 62 | ||||
| -rw-r--r-- | include/linux/nmi.h | 2 | ||||
| -rw-r--r-- | kernel/sysctl.c | 35 | ||||
| -rw-r--r-- | kernel/watchdog.c | 81 |
5 files changed, 97 insertions, 89 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 01aa47d3b6ab..71eecb263250 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -2236,8 +2236,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted. nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels Format: [panic,][nopanic,][num] - Valid num: 0 + Valid num: 0 or 1 0 - turn nmi_watchdog off + 1 - turn nmi_watchdog on When panic is specified, panic when an NMI watchdog timeout occurs (or 'nopanic' to override the opposite default). @@ -2464,7 +2465,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted. nousb [USB] Disable the USB subsystem - nowatchdog [KNL] Disable the lockup detector (NMI watchdog). + nowatchdog [KNL] Disable both lockup detectors, i.e. + soft-lockup and NMI watchdog (hard-lockup). nowb [ARM] diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt index 83ab25660fc9..99d7eb3a1416 100644 --- a/Documentation/sysctl/kernel.txt +++ b/Documentation/sysctl/kernel.txt @@ -77,12 +77,14 @@ show up in /proc/sys/kernel: - shmmax [ sysv ipc ] - shmmni - softlockup_all_cpu_backtrace +- soft_watchdog - stop-a [ SPARC only ] - sysrq ==> Documentation/sysrq.txt - sysctl_writes_strict - tainted - threads-max - unknown_nmi_panic +- watchdog - watchdog_thresh - version @@ -417,16 +419,23 @@ successful IPC object allocation. nmi_watchdog: -Enables/Disables the NMI watchdog on x86 systems. When the value is -non-zero the NMI watchdog is enabled and will continuously test all -online cpus to determine whether or not they are still functioning -properly. Currently, passing "nmi_watchdog=" parameter at boot time is -required for this function to work. +This parameter can be used to control the NMI watchdog +(i.e. the hard lockup detector) on x86 systems. -If LAPIC NMI watchdog method is in use (nmi_watchdog=2 kernel -parameter), the NMI watchdog shares registers with oprofile. By -disabling the NMI watchdog, oprofile may have more registers to -utilize. + 0 - disable the hard lockup detector + 1 - enable the hard lockup detector + +The hard lockup detector monitors each CPU for its ability to respond to +timer interrupts. The mechanism utilizes CPU performance counter registers +that are programmed to generate Non-Maskable Interrupts (NMIs) periodically +while a CPU is busy. Hence, the alternative name 'NMI watchdog'. + +The NMI watchdog is disabled by default if the kernel is running as a guest +in a KVM virtual machine. This default can be overridden by adding + + nmi_watchdog=1 + +to the guest kernel command line (see Documentation/kernel-parameters.txt). ============================================================== @@ -816,6 +825,22 @@ NMI. ============================================================== +soft_watchdog + +This parameter can be used to control the soft lockup detector. + + 0 - disable the soft lockup detector + 1 - enable the soft lockup detector + +The soft lockup detector monitors CPUs for threads that are hogging the CPUs +without rescheduling voluntarily, and thus prevent the 'watchdog/N' threads +from running. The mechanism depends on the CPUs ability to respond to timer +interrupts which are needed for the 'watchdog/N' threads to be woken up by +the watchdog timer function, otherwise the NMI watchdog - if enabled - can +detect a hard lockup condition. + +============================================================== + tainted: Non-zero if the kernel has been tainted. Numeric values, which @@ -858,6 +883,25 @@ example. If a system hangs up, try pressing the NMI switch. ============================================================== +watchdog: + +This parameter can be used to disable or enable the soft lockup detector +_and_ the NMI watchdog (i.e. the hard lockup detector) at the same time. + + 0 - disable both lockup detectors + 1 - enable both lockup detectors + +The soft lockup detector and the NMI watchdog can also be disabled or +enabled individually, using the soft_watchdog and nmi_watchdog parameters. +If the watchdog parameter is read, for example by executing + + cat /proc/sys/kernel/watchdog + +the output of this command (0 or 1) shows the logical OR of soft_watchdog +and nmi_watchdog. + +============================================================== + watchdog_thresh: This value can be used to control the frequency of hrtimer and NMI diff --git a/include/linux/nmi.h b/include/linux/nmi.h index 5b5450585b8a..0426357297d5 100644 --- a/include/linux/nmi.h +++ b/include/linux/nmi.h @@ -82,8 +82,6 @@ extern int proc_soft_watchdog(struct ctl_table *, int , void __user *, size_t *, loff_t *); extern int proc_watchdog_thresh(struct ctl_table *, int , void __user *, size_t *, loff_t *); -extern int proc_dowatchdog(struct ctl_table *, int , - void __user *, size_t *, loff_t *); #endif #ifdef CONFIG_HAVE_ACPI_APEI_NMI diff --git a/kernel/sysctl.c b/kernel/sysctl.c index ce410bb9f2e1..245e7dcc3741 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -846,7 +846,7 @@ static struct ctl_table kern_table[] = { .data = &watchdog_user_enabled, .maxlen = sizeof (int), .mode = 0644, - .proc_handler = proc_dowatchdog, + .proc_handler = proc_watchdog, .extra1 = &zero, .extra2 = &one, }, @@ -855,11 +855,33 @@ static struct ctl_table kern_table[] = { .data = &watchdog_thresh, .maxlen = sizeof(int), .mode = 0644, - .proc_handler = proc_dowatchdog, + .proc_handler = proc_watchdog_thresh, .extra1 = &zero, .extra2 = &sixty, }, { + .procname = "nmi_watchdog", + .data = &nmi_watchdog_enabled, + .maxlen = sizeof (int), + .mode = 0644, + .proc_handler = proc_nmi_watchdog, + .extra1 = &zero, +#if defined(CONFIG_HAVE_NMI_WATCHDOG) || defined(CONFIG_HARDLOCKUP_DETECTOR) + .extra2 = &one, +#else + .extra2 = &zero, +#endif + }, + { + .procname = "soft_watchdog", + .data = &soft_watchdog_enabled, + .maxlen = sizeof (int), + .mode = 0644, + .proc_handler = proc_soft_watchdog, + .extra1 = &zero, + .extra2 = &one, + }, + { .procname = "softlockup_panic", .data = &softlockup_panic, .maxlen = sizeof(int), @@ -879,15 +901,6 @@ static struct ctl_table kern_table[] = { .extra2 = &one, }, #endif /* CONFIG_SMP */ - { - .procname = "nmi_watchdog", - .data = &watchdog_user_enabled, - .maxlen = sizeof (int), - .mode = 0644, - .proc_handler = proc_dowatchdog, - .extra1 = &zero, - .extra2 = &one, - }, #endif #if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86) { diff --git a/kernel/watchdog.c b/kernel/watchdog.c index fd2b6dc14486..63d702885686 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -110,15 +110,9 @@ static int __init hardlockup_panic_setup(char *str) else if (!strncmp(str, "nopanic", 7)) hardlockup_panic = 0; else if (!strncmp(str, "0", 1)) - watchdog_user_enabled = 0; - else if (!strncmp(str, "1", 1) || !strncmp(str, "2", 1)) { - /* - * Setting 'nmi_watchdog=1' or 'nmi_watchdog=2' (legacy option) - * has the same effect. - */ - watchdog_user_enabled = 1; - watchdog_enable_hardlockup_detector(true); - } + watchdog_enabled &= ~NMI_WATCHDOG_ENABLED; + else if (!strncmp(str, "1", 1)) + watchdog_enabled |= NMI_WATCHDOG_ENABLED; return 1; } __setup("nmi_watchdog=", hardlockup_panic_setup); @@ -137,19 +131,18 @@ __setup("softlockup_panic=", softlockup_panic_setup); static int __init nowatchdog_setup(char *str) { - watchdog_user_enabled = 0; + watchdog_enabled = 0; return 1; } __setup("nowatchdog", nowatchdog_setup); -/* deprecated */ static int __init nosoftlockup_setup(char *str) { - watchdog_user_enabled = 0; + watchdog_enabled &= ~SOFT_WATCHDOG_ENABLED; return 1; } __setup("nosoftlockup", nosoftlockup_setup); -/* */ + #ifdef CONFIG_SMP static int __init softlockup_all_cpu_backtrace_setup(char *str) { @@ -264,10 +257,11 @@ static int is_softlockup(unsigned long touch_ts) { unsigned long now = get_timestamp(); - /* Warn about unreasonable delays: */ - if (time_after(now, touch_ts + get_softlockup_thresh())) - return now - touch_ts; - + if (watchdog_enabled & SOFT_WATCHDOG_ENABLED) { + /* Warn about unreasonable delays. */ + if (time_after(now, touch_ts + get_softlockup_thresh())) + return now - touch_ts; + } return 0; } @@ -532,6 +526,10 @@ 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; + /* * Some kernels need to default hard lockup detection to * 'disabled', for example a guest on a hypervisor. @@ -856,59 +854,12 @@ out: mutex_unlock(&watchdog_proc_mutex); return err; } - -/* - * 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; - bool old_hardlockup; - - mutex_lock(&watchdog_proc_mutex); - old_thresh = ACCESS_ONCE(watchdog_thresh); - old_enabled = ACCESS_ONCE(watchdog_user_enabled); - old_hardlockup = watchdog_hardlockup_detector_is_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) { - /* - * Prevent a change in watchdog_thresh accidentally overriding - * the enablement of the hardlockup detector. - */ - if (watchdog_user_enabled != old_enabled) - watchdog_enable_hardlockup_detector(true); - 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; - watchdog_enable_hardlockup_detector(old_hardlockup); - } -out: - mutex_unlock(&watchdog_proc_mutex); - return err; -} #endif /* CONFIG_SYSCTL */ void __init lockup_detector_init(void) { set_sample_period(); - if (watchdog_user_enabled) + if (watchdog_enabled) watchdog_enable_all_cpus(false); } |