watchdog: new definitions and variables, initialization (84d56e66) · Commits · 戴 / test

The hardlockup and softockup had always been tied together. Due to the request of KVM folks, they had a need to have one enabled but not the other. Internally rework the code to split things apart more cleanly. There is a bunch of churn here, but the end result should be code that should be easier to maintain and fix without knowing the internals of what is going on. This patch (of 9): Introduce new definitions and variables to separate the user interface in /proc/sys/kernel from the internal run state of the lockup detectors. The internal run state is represented by two bits in a new variable that is named 'watchdog_enabled'. This helps simplify the code, for example: - In order to check if any of the two lockup detectors is enabled, it is sufficient to check if 'watchdog_enabled' is not zero. - In order to enable/disable one or both lockup detectors, it is sufficient to set/clear one or both bits in 'watchdog_enabled'. - Concurrent updates of 'watchdog_enabled' need not be synchronized via a spinlock or a mutex. Updates can either be atomic or concurrency can be detected by using 'cmpxchg'. 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>

include/linux/nmi.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -68,6 +68,8 @@ static inline bool trigger_allbutself_cpu_backtrace(void)
		#ifdef CONFIG_LOCKUP_DETECTOR
		int hw_nmi_is_cpu_stuck(struct pt_regs *);
		u64 hw_nmi_get_sample_period(int watchdog_thresh);
		extern int nmi_watchdog_enabled;
		extern int soft_watchdog_enabled;
		extern int watchdog_user_enabled;
		extern int watchdog_thresh;
		extern int sysctl_softlockup_all_cpu_backtrace;

kernel/watchdog.c

+26 −1

Original line number	Diff line number	Diff line
		@@ -24,8 +24,33 @@
		#include <linux/kvm_para.h>
		#include <linux/perf_event.h>

		int watchdog_user_enabled = 1;
		/*
		* The run state of the lockup detectors is controlled by the content of the
		* 'watchdog_enabled' variable. Each lockup detector has its dedicated bit -
		* bit 0 for the hard lockup detector and bit 1 for the soft lockup detector.
		*
		* 'watchdog_user_enabled', 'nmi_watchdog_enabled' and 'soft_watchdog_enabled'
		* are variables that are only used as an 'interface' between the parameters
		* in /proc/sys/kernel and the internal state bits in 'watchdog_enabled'. The
		* 'watchdog_thresh' variable is handled differently because its value is not
		* boolean, and the lockup detectors are 'suspended' while 'watchdog_thresh'
		* is equal zero.
		*/
		#define NMI_WATCHDOG_ENABLED_BIT 0
		#define SOFT_WATCHDOG_ENABLED_BIT 1
		#define NMI_WATCHDOG_ENABLED (1 << NMI_WATCHDOG_ENABLED_BIT)
		#define SOFT_WATCHDOG_ENABLED (1 << SOFT_WATCHDOG_ENABLED_BIT)

		#ifdef CONFIG_HARDLOCKUP_DETECTOR
		static unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED\|NMI_WATCHDOG_ENABLED;
		#else
		static unsigned long __read_mostly watchdog_enabled = SOFT_WATCHDOG_ENABLED;
		#endif
		int __read_mostly nmi_watchdog_enabled;
		int __read_mostly soft_watchdog_enabled;
		int __read_mostly watchdog_user_enabled;
		int __read_mostly watchdog_thresh = 10;

		#ifdef CONFIG_SMP
		int __read_mostly sysctl_softlockup_all_cpu_backtrace;
		#else

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