Re: [PATCH 1/1] function trace: fix a bug of single thread function trace

[Ingo Molnar <mingo@elte.hu>]

* Liming Wang <liming.wang@windriver.com> wrote:

> Impact: fix a bug in ftrace_update_pid_func
> 
> When disabling single thread function trace using
> "echo -1 > set_ftrace_pid", the normal function trace
> has to restore to original function, otherwise the normal
> function trace will not work well.
> Without this commit, something like below:
> 
> 	$ ps |grep 850
> 	  850 root      2556 S    -/bin/sh
> 	$ echo 850 > /debug/tracing/set_ftrace_pid
> 	$ echo function > /debug/tracing/current_tracer
> 	$ echo 1 > /debug/tracing/tracing_enabled
> 	$ sleep 1
> 	$ echo 0 > /debug/tracing/tracing_enabled
> 	$ cat /debug/tracing/trace_pipe |wc -l
> 	59704
> 	$ echo -1 > /debug/tracing/set_ftrace_pid
> 	$ echo 1 > /debug/tracing/tracing_enabled
> 	$ sleep 1
> 	$ echo 0 > /debug/tracing/tracing_enabled
> 	$ more /debug/tracing/trace_pipe
> 		<====== nothing output now!
> 			it should output trace record.
> 
> Signed-off-by: Liming Wang <liming.wang@windriver.com>
> ---
>  kernel/trace/ftrace.c |    6 ++----
>  1 files changed, 2 insertions(+), 4 deletions(-)

applied to tip/tracing/ftrace, thanks!

	Ingo