[LTP] [PATCH] ftrace_stress_test: check if tracing_enabled is supported

[Steven Rostedt <srostedt@redhat.com>]

On Thu, 2016-02-04 at 16:11 +0100, Cyril Hrubis wrote:

> Also looking at the stress test all it does is writing to various files
> (in several background loops) that store tracing parameters. Is that
> even reasonable test? I guess that it can find out race conditions
> between functions that handle the write for the options...

I don't use the LTP tests for ftrace, so I wouldn't know.

> 
> And it uses the tracing_on file as well. So we can just skip starting
> the loop writes to the ftrace_enabled file if it's not present.
> 

ftrace_enabled is completely different. It disables function tracing
capabilities (and should be avoided
if /sys/kernel/debug/tracing/options/function-trace is present. As that
will only disable function hooks for tracing,
where /proc/sys/kernel/ftrace_enabled disables *all* hooks (including
those for live kernel patching). Which I need to make a patch to prevent
that :-/

-- Steve