pstore/ftrace: Convert to its own enable/disable debugfs knob
With this patch we no longer reuse function tracer infrastructure, now
we register our own tracer back-end via a debugfs knob.
It's a bit more code, but that is the only downside. On the bright side we
have:
- Ability to make persistent_ram module removable (when needed, we can
move ftrace_ops struct into a module). Note that persistent_ram is still
not removable for other reasons, but with this patch it's just one
thing less to worry about;
- Pstore part is more isolated from the generic function tracer. We tried
it already by registering our own tracer in available_tracers, but that
way we're loosing ability to see the traces while we record them to
pstore. This solution is somewhere in the middle: we only register
"internal ftracer" back-end, but not the "front-end";
- When there is only pstore tracing enabled, the kernel will only write
to the pstore buffer, omitting function tracer buffer (which, of course,
still can be enabled via 'echo function > current_tracer').
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
diff --git a/Documentation/ramoops.txt b/Documentation/ramoops.txt
index 197ad59..69b3cac 100644
--- a/Documentation/ramoops.txt
+++ b/Documentation/ramoops.txt
@@ -102,9 +102,7 @@
file. Here is an example of usage:
# mount -t debugfs debugfs /sys/kernel/debug/
- # cd /sys/kernel/debug/tracing
- # echo function > current_tracer
- # echo 1 > options/func_pstore
+ # echo 1 > /sys/kernel/debug/pstore/record_ftrace
# reboot -f
[...]
# mount -t pstore pstore /mnt/