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authorStephen Kitt <steve@sk2.org>2020-04-29 23:57:56 +0300
committerJonathan Corbet <corbet@lwn.net>2020-05-05 18:53:45 +0300
commit50cdae76b8d021f31ea07af3bb30983486b79df8 (patch)
tree432b079776db2780d18dc5764b05510ffcd2ea14 /Documentation/admin-guide/sysctl
parentc624adc9cb6e6e8f1c0230a7775add700bc2409b (diff)
downloadlinux-50cdae76b8d021f31ea07af3bb30983486b79df8.tar.xz
docs: sysctl/kernel: document ftrace entries
Based on the ftrace documentation, the tp_printk boot parameter documentation, and the implementation in kernel/trace/trace.c. Signed-off-by: Stephen Kitt <steve@sk2.org> Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Link: https://lore.kernel.org/r/20200429205757.8677-1-steve@sk2.org Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Diffstat (limited to 'Documentation/admin-guide/sysctl')
-rw-r--r--Documentation/admin-guide/sysctl/kernel.rst48
1 files changed, 48 insertions, 0 deletions
diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
index 706c2158ad25..5de73768f14e 100644
--- a/Documentation/admin-guide/sysctl/kernel.rst
+++ b/Documentation/admin-guide/sysctl/kernel.rst
@@ -265,6 +265,27 @@ domain names are in general different. For a detailed discussion
see the ``hostname(1)`` man page.
+ftrace_dump_on_oops
+===================
+
+Determines whether ``ftrace_dump()`` should be called on an oops (or
+kernel panic). This will output the contents of the ftrace buffers to
+the console. This is very useful for capturing traces that lead to
+crashes and outputting them to a serial console.
+
+= ===================================================
+0 Disabled (default).
+1 Dump buffers of all CPUs.
+2 Dump the buffer of the CPU that triggered the oops.
+= ===================================================
+
+
+ftrace_enabled, stack_tracer_enabled
+====================================
+
+See :doc:`/trace/ftrace`.
+
+
hardlockup_all_cpu_backtrace
============================
@@ -1191,6 +1212,33 @@ If a value outside of this range is written to ``threads-max`` an
``EINVAL`` error occurs.
+traceoff_on_warning
+===================
+
+When set, disables tracing (see :doc:`/trace/ftrace`) when a
+``WARN()`` is hit.
+
+
+tracepoint_printk
+=================
+
+When tracepoints are sent to printk() (enabled by the ``tp_printk``
+boot parameter), this entry provides runtime control::
+
+ echo 0 > /proc/sys/kernel/tracepoint_printk
+
+will stop tracepoints from being sent to printk(), and::
+
+ echo 1 > /proc/sys/kernel/tracepoint_printk
+
+will send them to printk() again.
+
+This only works if the kernel was booted with ``tp_printk`` enabled.
+
+See :doc:`/admin-guide/kernel-parameters` and
+:doc:`/trace/boottime-trace`.
+
+
unknown_nmi_panic
=================