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docs: sysctl/kernel: document ftrace entries

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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>
This commit is contained in:
Stephen Kitt 2020-04-29 22:57:56 +02:00 committed by Jonathan Corbet
parent c624adc9cb
commit 50cdae76b8
1 changed files with 48 additions and 0 deletions
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48
Documentation/admin-guide/sysctl/kernel.rst
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@ -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
=================