diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/watchdog.c | 95 |
1 files changed, 47 insertions, 48 deletions
diff --git a/kernel/watchdog.c b/kernel/watchdog.c index 5693afd2b8ea..84886319d7b0 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -32,15 +32,17 @@ static DEFINE_MUTEX(watchdog_mutex); #if defined(CONFIG_HARDLOCKUP_DETECTOR) || defined(CONFIG_HAVE_NMI_WATCHDOG) -unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED | - NMI_WATCHDOG_ENABLED; +# define WATCHDOG_DEFAULT (SOFT_WATCHDOG_ENABLED | NMI_WATCHDOG_ENABLED) +# define NMI_WATCHDOG_DEFAULT 1 #else -unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED; +# define WATCHDOG_DEFAULT (SOFT_WATCHDOG_ENABLED) +# define NMI_WATCHDOG_DEFAULT 0 #endif -int __read_mostly nmi_watchdog_user_enabled; -int __read_mostly soft_watchdog_user_enabled; -int __read_mostly watchdog_user_enabled; +unsigned long __read_mostly watchdog_enabled; +int __read_mostly watchdog_user_enabled = 1; +int __read_mostly nmi_watchdog_user_enabled = NMI_WATCHDOG_DEFAULT; +int __read_mostly soft_watchdog_user_enabled = 1; int __read_mostly watchdog_thresh = 10; struct cpumask watchdog_allowed_mask __read_mostly; @@ -65,7 +67,7 @@ unsigned int __read_mostly hardlockup_panic = */ void __init hardlockup_detector_disable(void) { - watchdog_enabled &= ~NMI_WATCHDOG_ENABLED; + nmi_watchdog_user_enabled = 0; } static int __init hardlockup_panic_setup(char *str) @@ -75,9 +77,9 @@ static int __init hardlockup_panic_setup(char *str) else if (!strncmp(str, "nopanic", 7)) hardlockup_panic = 0; else if (!strncmp(str, "0", 1)) - watchdog_enabled &= ~NMI_WATCHDOG_ENABLED; + nmi_watchdog_user_enabled = 0; else if (!strncmp(str, "1", 1)) - watchdog_enabled |= NMI_WATCHDOG_ENABLED; + nmi_watchdog_user_enabled = 1; return 1; } __setup("nmi_watchdog=", hardlockup_panic_setup); @@ -132,6 +134,23 @@ void __weak watchdog_nmi_disable(unsigned int cpu) */ void __weak watchdog_nmi_reconfigure(bool run) { } +/** + * lockup_detector_update_enable - Update the sysctl enable bit + * + * Caller needs to make sure that the NMI/perf watchdogs are off, so this + * can't race with watchdog_nmi_disable(). + */ +static void lockup_detector_update_enable(void) +{ + watchdog_enabled = 0; + if (!watchdog_user_enabled) + return; + if (nmi_watchdog_user_enabled) + watchdog_enabled |= NMI_WATCHDOG_ENABLED; + if (soft_watchdog_user_enabled) + watchdog_enabled |= SOFT_WATCHDOG_ENABLED; +} + #ifdef CONFIG_SOFTLOCKUP_DETECTOR /* Global variables, exported for sysctl */ @@ -160,14 +179,14 @@ __setup("softlockup_panic=", softlockup_panic_setup); static int __init nowatchdog_setup(char *str) { - watchdog_enabled = 0; + watchdog_user_enabled = 0; return 1; } __setup("nowatchdog", nowatchdog_setup); static int __init nosoftlockup_setup(char *str) { - watchdog_enabled &= ~SOFT_WATCHDOG_ENABLED; + soft_watchdog_user_enabled = 0; return 1; } __setup("nosoftlockup", nosoftlockup_setup); @@ -521,12 +540,13 @@ static void softlockup_unpark_threads(void) softlockup_update_smpboot_threads(); } -static void softlockup_reconfigure_threads(bool enabled) +static void softlockup_reconfigure_threads(void) { watchdog_nmi_reconfigure(false); softlockup_park_all_threads(); set_sample_period(); - if (enabled) + lockup_detector_update_enable(); + if (watchdog_enabled && watchdog_thresh) softlockup_unpark_threads(); watchdog_nmi_reconfigure(true); } @@ -546,6 +566,8 @@ static __init void softlockup_init_threads(void) * If sysctl is off and watchdog got disabled on the command line, * nothing to do here. */ + lockup_detector_update_enable(); + if (!IS_ENABLED(CONFIG_SYSCTL) && !(watchdog_enabled && watchdog_thresh)) return; @@ -559,7 +581,7 @@ static __init void softlockup_init_threads(void) mutex_lock(&watchdog_mutex); softlockup_threads_initialized = true; - softlockup_reconfigure_threads(watchdog_enabled && watchdog_thresh); + softlockup_reconfigure_threads(); mutex_unlock(&watchdog_mutex); } @@ -569,9 +591,10 @@ static inline void watchdog_unpark_threads(void) { } static inline int watchdog_enable_all_cpus(void) { return 0; } static inline void watchdog_disable_all_cpus(void) { } static inline void softlockup_init_threads(void) { } -static void softlockup_reconfigure_threads(bool enabled) +static void softlockup_reconfigure_threads(void) { watchdog_nmi_reconfigure(false); + lockup_detector_update_enable(); watchdog_nmi_reconfigure(true); } #endif /* !CONFIG_SOFTLOCKUP_DETECTOR */ @@ -612,7 +635,7 @@ static void proc_watchdog_update(void) { /* Remove impossible cpus to keep sysctl output clean. */ cpumask_and(&watchdog_cpumask, &watchdog_cpumask, cpu_possible_mask); - softlockup_reconfigure_threads(watchdog_enabled && watchdog_thresh); + softlockup_reconfigure_threads(); } /* @@ -630,48 +653,24 @@ static void proc_watchdog_update(void) 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; + int err, old, *param = table->data; cpu_hotplug_disable(); mutex_lock(&watchdog_mutex); - /* - * 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; + /* + * On read synchronize the userspace interface. This is a + * racy snapshot. + */ + *param = (watchdog_enabled & which) != 0; err = proc_dointvec_minmax(table, write, buffer, lenp, ppos); } else { + old = READ_ONCE(*param); 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); - - if (old != new) + if (!err && old != READ_ONCE(*param)) proc_watchdog_update(); } -out: mutex_unlock(&watchdog_mutex); cpu_hotplug_enable(); return err; |