From 6e7458a6f074c71e74cda31c483114e65ea0f570 Mon Sep 17 00:00:00 2001 From: Ulrich Obergfell Date: Mon, 13 Oct 2014 15:55:35 -0700 Subject: 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 Signed-off-by: Andrew Jones Signed-off-by: Don Zickus Signed-off-by: Don Zickus Cc: Stephen Rothwell Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/nmi.h | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'include/linux') 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, -- cgit v1.2.3