diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 01aa47d3b6ab607e6a66f2a6a827b4b1afe4da73..71eecb263250c5f5f44fe4d45dcb1a405ed9bedb 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 83ab25660fc961de2d498b3a56724ecc09f950b2..99d7eb3a14164f68ea20c8790db4c138dcb55be9 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 5b5450585b8a8359331a1ee5fc842b7bdb976c53..0426357297d55cba69ef716abc4b666a5a03c1aa 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 ce410bb9f2e103e0fcfda7d7b844948a0a28fbce..245e7dcc3741a59c051c4d0dad0ca953071d6991 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,
},
@@ -855,10 +855,32 @@ 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,
@@ -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 fd2b6dc14486a8e3671ae0cc8bd89b5e82ba636a..63d7028856867e2fd7af7782a8923be6d6b9b1ad 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 @@ int proc_watchdog_thresh(struct ctl_table *table, int write,
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);
}