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authorUlrich Obergfell <uobergfe@redhat.com>2014-10-13 15:55:35 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-10-14 02:18:27 +0200
commit6e7458a6f074c71e74cda31c483114e65ea0f570 (patch)
treed942b6b9ec308d66f64649b94d088b02bf2e6309 /include/linux
parent8a1db92830d0a71e1429725992eb91470214c820 (diff)
kernel/watchdog.c: control hard lockup detection default
In some cases we don't want hard lockup detection enabled by default. An example is when running as a guest. Introduce watchdog_enable_hardlockup_detector(bool) allowing those cases to disable hard lockup detection. This must be executed early by the boot processor from e.g. smp_prepare_boot_cpu, in order to allow kernel command line arguments to override it, as well as to avoid hard lockup detection being enabled before we've had a chance to indicate that it's unwanted. In summary, initial boot: default=enabled smp_prepare_boot_cpu watchdog_enable_hardlockup_detector(false): default=disabled cmdline has 'nmi_watchdog=1': default=enabled The running kernel still has the ability to enable/disable at any time with /proc/sys/kernel/nmi_watchdog us usual. However even when the default has been overridden /proc/sys/kernel/nmi_watchdog will initially show '1'. To truly turn it on one must disable/enable it, i.e. echo 0 > /proc/sys/kernel/nmi_watchdog echo 1 > /proc/sys/kernel/nmi_watchdog This patch will be immediately useful for KVM with the next patch of this series. Other hypervisor guest types may find it useful as well. [akpm@linux-foundation.org: fix build] [dzickus@redhat.com: fix compile issues on sparc] Signed-off-by: Ulrich Obergfell <uobergfe@redhat.com> Signed-off-by: Andrew Jones <drjones@redhat.com> Signed-off-by: Don Zickus <dzickus@redhat.com> Signed-off-by: Don Zickus <dzickus@redhat.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux')
-rw-r--r--include/linux/nmi.h13
1 files changed, 13 insertions, 0 deletions
diff --git a/include/linux/nmi.h b/include/linux/nmi.h
index 1d2a6ab6b8bb..9b2022ab4d85 100644
--- a/include/linux/nmi.h
+++ b/include/linux/nmi.h
@@ -24,6 +24,19 @@ static inline void touch_nmi_watchdog(void)
}
#endif
+#if defined(CONFIG_HARDLOCKUP_DETECTOR)
+extern void watchdog_enable_hardlockup_detector(bool val);
+extern bool watchdog_hardlockup_detector_is_enabled(void);
+#else
+static inline void watchdog_enable_hardlockup_detector(bool val)
+{
+}
+static inline bool watchdog_hardlockup_detector_is_enabled(void)
+{
+ return true;
+}
+#endif
+
/*
* Create trigger_all_cpu_backtrace() out of the arch-provided
* base function. Return whether such support was available,