From: Frederic Weisbecker Date: Thu, 6 Jun 2013 13:42:53 +0000 (+0200) Subject: watchdog: Register / unregister watchdog kthreads on sysctl control X-Git-Tag: v3.11-rc1~9^2~3^2~3 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b8900bc0217fac8e68085997bee2f05e6db931a2;p=pandora-kernel.git watchdog: Register / unregister watchdog kthreads on sysctl control The user activation/deactivation of the watchdog through boot parameters or systcl is currently implemented with a dance involving kthreads parking and unparking methods: the threads are unconditionally registered on boot and they park as soon as the user want the watchdog to be disabled. This method involves a few noisy details to handle though: the watchdog kthreads may be unparked anytime due to hotplug operations, after which the watchdog internals have to decide to park again if it is user-disabled. As a result the setup() and unpark() methods need to be able to request a reparking. This is not currently supported in the kthread infrastructure so this piece of the watchdog code only works halfway. Besides, unparking/reparking the watchdog kthreads consume unnecessary cputime on hotplug operations when those could be simply ignored in the first place. As suggested by Srivatsa, let's instead only register the watchdog threads when they are needed. This way we don't need to think about hotplug operations and we don't burden the CPU onlining when the watchdog is simply disabled. Suggested-by: Srivatsa S. Bhat Signed-off-by: Frederic Weisbecker Cc: Srivatsa S. Bhat Cc: Anish Singh Cc: Steven Rostedt Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Li Zhong Cc: Don Zickus --- Reading git-diff-tree failed