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-rw-r--r--Documentation/sysctl/kernel.txt21
1 files changed, 21 insertions, 0 deletions
diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index c831001c45f1..e5d528e0c46e 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -923,6 +923,27 @@ and nmi_watchdog.
==============================================================
+watchdog_cpumask:
+
+This value can be used to control on which cpus the watchdog may run.
+The default cpumask is all possible cores, but if NO_HZ_FULL is
+enabled in the kernel config, and cores are specified with the
+nohz_full= boot argument, those cores are excluded by default.
+Offline cores can be included in this mask, and if the core is later
+brought online, the watchdog will be started based on the mask value.
+
+Typically this value would only be touched in the nohz_full case
+to re-enable cores that by default were not running the watchdog,
+if a kernel lockup was suspected on those cores.
+
+The argument value is the standard cpulist format for cpumasks,
+so for example to enable the watchdog on cores 0, 2, 3, and 4 you
+might say:
+
+ echo 0,2-4 > /proc/sys/kernel/watchdog_cpumask
+
+==============================================================
+
watchdog_thresh:
This value can be used to control the frequency of hrtimer and NMI