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;
*/
void __init hardlockup_detector_disable(void)
{
- watchdog_enabled &= ~NMI_WATCHDOG_ENABLED;
+ nmi_watchdog_user_enabled = 0;
}
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);
*/
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 */
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);
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);
}
* 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;
mutex_lock(&watchdog_mutex);
softlockup_threads_initialized = true;
- softlockup_reconfigure_threads(watchdog_enabled && watchdog_thresh);
+ softlockup_reconfigure_threads();
mutex_unlock(&watchdog_mutex);
}
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 */
{
/* 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();
}
/*
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;
projects / mirror_ubuntu-bionic-kernel.git / blobdiff