From a01fdc897fa56ffb596d0a0cd7ea2ab3bd8398c5 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Google)" Date: Thu, 20 Oct 2022 21:00:56 -0400 Subject: tracing: Add trace_trigger kernel command line option Allow triggers to be enabled at kernel boot up. For example: trace_trigger="sched_switch.stacktrace if prev_state == 2" The above will enable the stacktrace trigger on top of the sched_switch event and only trigger if its prev_state is 2 (TASK_UNINTERRUPTIBLE). Then at boot up, a stacktrace will trigger and be recorded in the tracing ring buffer every time the sched_switch happens where the previous state is TASK_INTERRUPTIBLE. Another useful trigger would be "traceoff" which can stop tracing on an event if a field of the event matches a certain value defined by the filter ("if" statement). Link: https://lore.kernel.org/linux-trace-kernel/20221020210056.0d8d0a5b@gandalf.local.home Signed-off-by: Steven Rostedt (Google) --- Documentation/admin-guide/kernel-parameters.txt | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) (limited to 'Documentation/admin-guide') diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index a465d5242774..ccf91a4bf113 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -6257,6 +6257,25 @@ See also Documentation/trace/ftrace.rst "trace options" section. + trace_trigger=[trigger-list] + [FTRACE] Add a event trigger on specific events. + Set a trigger on top of a specific event, with an optional + filter. + + The format is is "trace_trigger=.[ if ],..." + Where more than one trigger may be specified that are comma deliminated. + + For example: + + trace_trigger="sched_switch.stacktrace if prev_state == 2" + + The above will enable the "stacktrace" trigger on the "sched_switch" + event but only trigger it if the "prev_state" of the "sched_switch" + event is "2" (TASK_UNINTERUPTIBLE). + + See also "Event triggers" in Documentation/trace/events.rst + + traceoff_on_warning [FTRACE] enable this option to disable tracing when a warning is hit. This turns off "tracing_on". Tracing can -- cgit v1.2.3