[PATCH v3 7/8] Documentation: tracing: boot: Add an example of tracing function-calls
From: Masami Hiramatsu <mhiramat@kernel.org>
Date: 2020-09-10 08:58:48
Also in:
linux-kselftest, lkml
Subsystem:
documentation, the rest, tracing · Maintainers:
Jonathan Corbet, Linus Torvalds, Steven Rostedt, Masami Hiramatsu
Add an example of tracing function calls on a specific function. Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> --- Documentation/trace/boottime-trace.rst | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+)
diff --git a/Documentation/trace/boottime-trace.rst b/Documentation/trace/boottime-trace.rst
index 1341b449acaa..c216f5695ae2 100644
--- a/Documentation/trace/boottime-trace.rst
+++ b/Documentation/trace/boottime-trace.rst@@ -168,6 +168,26 @@ is for tracing functions starting with "user\_", and others tracing The instance node also accepts event nodes so that each instance can customize its event tracing. +With the trigger action and kprobes, you can trace function-graph while +a function is called. For example, this will trace all function calls in +the pci_proc_init():: + + ftrace { + tracing_on = 0 + tracer = function_graph + event.kprobes { + start_event { + probes = "pci_proc_init" + actions = "traceon" + } + end_event { + probes = "pci_proc_init%return" + actions = "traceoff" + } + } + } + + This boot-time tracing also supports ftrace kernel parameters via boot config. For example, following kernel parameters::