Messages in this thread Patch in this message |  | | Date | Mon, 4 Jul 2016 10:21:39 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH] ftrace: move function_stats out of __initdata |
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On Mon, 4 Jul 2016 15:09:44 +0200 Arnd Bergmann <arnd@arndb.de> wrote:
> Not marking ftrace_init_tracefs() as __init causes a link time warning: > > WARNING: vmlinux.o(.text+0xf5fcc): Section mismatch in reference from the function ftrace_init_tracefs() to the (unknown reference) .init.data:(unknown) > > The problem here is that ftrace_init_tracefs() now gets called by > init_tracer_tracefs(), which cannot be __init because it is called > post init-time from instance_mkdir(). The function calls to the > init-time ftrace_init_dyn_tracefs() and ftrace_profile_tracefs() > functions apparently only happen for the initial call to > ftrace_init_tracefs(), so we could safely ignore the warning, but > at the same time, it all gets inlined anyway and we may as well > remove the annotations. > > The alternative would be restructuring the code so we only call > trace_create_file() from init_tracer_tracefs(), but not the other > init-time functions. > > Signed-off-by: Arnd Bergmann <arnd@arndb.de> > Fixes: 345ddcc882d8 ("ftrace: Have set_ftrace_pid use the bitmap like events do")
I know about this, and this is not the fix. The issue is that ftrace_init_tracefs() has:
if (tr->flags & TRACE_ARRAY_FL_GLOBAL) { ftrace_init_dyn_tracefs(d_tracer); ftrace_profile_tracefs(d_tracer); }
Where that condition is only true on boot up. Hence, those two functions will never get called during normal runtime situations.
I have a patch to fix this, I just haven't gotten around to running it through my test suite, or even committing it for that matter. It's a US holiday today and I wont be doing any more with this till tomorrow.
Below is the patch. Feel free to test it out (I haven't done much with it yet).
-- Steve
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 8b488f4dd8e8..84752c8e28b5 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -5539,16 +5539,20 @@ static const struct file_operations ftrace_pid_fops = { void ftrace_init_tracefs(struct trace_array *tr, struct dentry *d_tracer) { - /* Only the top level directory has the dyn_tracefs and profile */ - if (tr->flags & TRACE_ARRAY_FL_GLOBAL) { - ftrace_init_dyn_tracefs(d_tracer); - ftrace_profile_tracefs(d_tracer); - } - trace_create_file("set_ftrace_pid", 0644, d_tracer, tr, &ftrace_pid_fops); } +void __init ftrace_init_tracefs_toplevel(struct trace_array *tr, + struct dentry *d_tracer) +{ + /* Only the top level directory has the dyn_tracefs and profile */ + WARN_ON(!(tr->flags & TRACE_ARRAY_FL_GLOBAL)); + + ftrace_init_dyn_tracefs(d_tracer); + ftrace_profile_tracefs(d_tracer); +} + /** * ftrace_kill - kill ftrace * diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 3d9f31b576f3..5fd53a7847bc 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -7369,6 +7369,7 @@ static __init int tracer_init_tracefs(void) return 0; init_tracer_tracefs(&global_trace, d_tracer); + ftrace_init_tracefs_toplevel(&global_trace, d_tracer); trace_create_file("tracing_thresh", 0644, d_tracer, &global_trace, &tracing_thresh_fops); diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index eaee458755a4..d751ed7c663b 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -857,6 +857,8 @@ void ftrace_init_array_ops(struct trace_array *tr, ftrace_func_t func); void ftrace_reset_array_ops(struct trace_array *tr); int using_ftrace_ops_list_func(void); void ftrace_init_tracefs(struct trace_array *tr, struct dentry *d_tracer); +void ftrace_init_tracefs_toplevel(struct trace_array *tr, + struct dentry *d_tracer); #else static inline int ftrace_trace_task(struct trace_array *tr) {
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