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* watchdog: add watchdog_cpumask sysctl to assist nohzChris Metcalf2015-06-241-0/+18
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Change the default behavior of watchdog so it only runs on the housekeeping cores when nohz_full is enabled at build and boot time. Allow modifying the set of cores the watchdog is currently running on with a new kernel.watchdog_cpumask sysctl. In the current system, the watchdog subsystem runs a periodic timer that schedules the watchdog kthread to run. However, nohz_full cores are designed to allow userspace application code running on those cores to have 100% access to the CPU. So the watchdog system prevents the nohz_full application code from being able to run the way it wants to, thus the motivation to suppress the watchdog on nohz_full cores, which this patchset provides by default. However, if we disable the watchdog globally, then the housekeeping cores can't benefit from the watchdog functionality. So we allow disabling it only on some cores. See Documentation/lockup-watchdogs.txt for more information. [jhubbard@nvidia.com: fix a watchdog crash in some configurations] Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com> Acked-by: Don Zickus <dzickus@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Ulrich Obergfell <uobergfe@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: John Hubbard <jhubbard@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* lockup-watchdogs: Fix a typoHarish Jenny K N2014-08-261-1/+1
| | | | | | | | s/BOOTPARAM_HARDLOCKUP_PANIC/BOOTPARAM_SOFTLOCKUP_PANIC Signed-off-by: Harish Jenny K N <harish_kandiga@mentor.com> Acked-by: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
* watchdog: Update documentationFernando Luis Vázquez Cao2012-02-111-0/+63
The soft and hard lockup detectors are now built on top of the hrtimer and perf subsystems. Update the documentation accordingly. Signed-off-by: Fernando Luis Vazquez Cao<fernando@oss.ntt.co.jp> Acked-by: Randy Dunlap <rdunlap@xenotime.net> Signed-off-by: Don Zickus <dzickus@redhat.com> Link: http://lkml.kernel.org/r/1328827342-6253-1-git-send-email-dzickus@redhat.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
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