2008-12-02 02:49:11

by tip-bot for Liming Wang

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

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 <[email protected]>
---
kernel/trace/ftrace.c | 6 ++----
1 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index cbf8b09..7540ef1 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -243,10 +243,8 @@ static void ftrace_update_pid_func(void)
set_ftrace_pid_function(func);
func = ftrace_pid_func;
} else {
- if (func != ftrace_pid_func)
- goto out;
-
- set_ftrace_pid_function(func);
+ if (func == ftrace_pid_func)
+ func = ftrace_pid_function;
}

#ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
--
1.6.0.3

2008-12-02 08:23:51

by Ingo Molnar

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

* Liming Wang <[email protected]> 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 <[email protected]>
> ---
> kernel/trace/ftrace.c | 6 ++----
> 1 files changed, 2 insertions(+), 4 deletions(-)

applied to tip/tracing/ftrace, thanks!

Ingo