kernel/watchdog.c: add sysctl knob hardlockup_panic

The only way to enable a hardlockup to panic the machine is to set
'nmi_watchdog=panic' on the kernel command line.

This makes it awkward for end users and folks who want to run automate
tests (like myself).

Mimic the softlockup_panic knob and create a /proc/sys/kernel/hardlockup_panic
knob.

Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: Ulrich Obergfell <uobergfe@redhat.com>
Acked-by: Jiri Kosina <jkosina@suse.cz>
Reviewed-by: Aaron Tomlin <atomlin@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/Documentation/lockup-watchdogs.txt b/Documentation/lockup-watchdogs.txt
index 22dd6af..4a6e33e 100644 (file)
--- a/Documentation/lockup-watchdogs.txt
+++ b/Documentation/lockup-watchdogs.txt
@@ -20,8 +20,9 @@ kernel mode for more than 10 seconds (see "Implementation" below for
 details), without letting other interrupts have a chance to run.
 Similarly to the softlockup case, the current stack trace is displayed
 upon detection and the system will stay locked up unless the default
-behavior is changed, which can be done through a compile time knob,
-"BOOTPARAM_HARDLOCKUP_PANIC", and a kernel parameter, "nmi_watchdog"
+behavior is changed, which can be done through a sysctl,
+'hardlockup_panic', a compile time knob, "BOOTPARAM_HARDLOCKUP_PANIC",
+and a kernel parameter, "nmi_watchdog"
 (see "Documentation/kernel-parameters.txt" for details).
 
 The panic option can be used in combination with panic_timeout (this

diff --git a/include/linux/sched.h b/include/linux/sched.h
index c115d61..5423b9c 100644 (file)
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -384,6 +384,7 @@ extern int proc_dowatchdog_thresh(struct ctl_table *table, int write,
                                  void __user *buffer,
                                  size_t *lenp, loff_t *ppos);
 extern unsigned int  softlockup_panic;
+extern unsigned int  hardlockup_panic;
 void lockup_detector_init(void);
 #else
 static inline void touch_softlockup_watchdog(void)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 1a5faa3..dc6858d 100644 (file)
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -888,6 +888,17 @@ static struct ctl_table kern_table[] = {
                .extra1         = &zero,
                .extra2         = &one,
        },
+#ifdef CONFIG_HARDLOCKUP_DETECTOR
+       {
+               .procname       = "hardlockup_panic",
+               .data           = &hardlockup_panic,
+               .maxlen         = sizeof(int),
+               .mode           = 0644,
+               .proc_handler   = proc_dointvec_minmax,
+               .extra1         = &zero,
+               .extra2         = &one,
+       },
+#endif
 #ifdef CONFIG_SMP
        {
                .procname       = "softlockup_all_cpu_backtrace",

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index f6b32b8..0a23125 100644 (file)
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -112,7 +112,7 @@ static unsigned long soft_lockup_nmi_warn;
  * Should we panic when a soft-lockup or hard-lockup occurs:
  */
 #ifdef CONFIG_HARDLOCKUP_DETECTOR
-static int hardlockup_panic =
+unsigned int __read_mostly hardlockup_panic =
                        CONFIG_BOOTPARAM_HARDLOCKUP_PANIC_VALUE;
 static unsigned long hardlockup_allcpu_dumped;
 /*