watchdog: enable the new user interface of the watchdog mechanism
With the current user interface of the watchdog mechanism it is only
possible to disable or enable both lockup detectors at the same time.
This series introduces new kernel parameters and changes the semantics of
some existing kernel parameters, so that the hard lockup detector and the
soft lockup detector can be disabled or enabled individually. With this
series applied, the user interface is as follows.
- parameters in /proc/sys/kernel
. soft_watchdog
This is a new parameter to control and examine the run state of
the soft lockup detector.
. nmi_watchdog
The semantics of this parameter have changed. It can now be used
to control and examine the run state of the hard lockup detector.
. watchdog
This parameter is still available to control the run state of both
lockup detectors at the same time. If this parameter is examined,
it shows the logical OR of soft_watchdog and nmi_watchdog.
. watchdog_thresh
The semantics of this parameter are not affected by the patch.
- kernel command line parameters
. nosoftlockup
The semantics of this parameter have changed. It can now be used
to disable the soft lockup detector at boot time.
. nmi_watchdog=0 or nmi_watchdog=1
Disable or enable the hard lockup detector at boot time. The patch
introduces '=1' as a new option.
. nowatchdog
The semantics of this parameter are not affected by the patch. It
is still available to disable both lockup detectors at boot time.
Also, remove the proc_dowatchdog() function which is no longer needed.
[dzickus@redhat.com: wrote changelog]
[dzickus@redhat.com: update documentation for kernel params and sysctl]
Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index fd2b6dc..63d7028 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -110,15 +110,9 @@
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 @@
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 @@
{
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 @@
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 @@
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);
}