linux-kernel - Re: [PATCH 2/4] ftrace/instances: Clear function triggers when removing instances

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Date:   Tue, 6 Jun 2017 23:07:17 +0530
From:   "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To:     Shuah Khan <shuah@...nel.org>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH 2/4] ftrace/instances: Clear function triggers when
 removing instances

On 2017/06/06 11:06AM, Shuah Khan wrote:
> On 05/16/2017 12:33 PM, Steven Rostedt wrote:
> > On Tue, 16 May 2017 23:14:23 +0530
> > "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com> wrote:
> > 
> >> On 2017/05/16 07:31PM, Naveen N. Rao wrote:
> >>> On 2017/05/15 10:20PM, Steven Rostedt wrote:  
> >>>> On Sun, 14 May 2017 01:01:02 +0530
> >>>> "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com> wrote:
> >>>>   
> >>>
> >>> [snip]
> >>>   
> >>>>> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> >>>>> index c4536c449021..3f2aed4ad1ed 100644
> >>>>> --- a/kernel/trace/trace.c
> >>>>> +++ b/kernel/trace/trace.c
> >>>>> @@ -7550,6 +7550,7 @@ static int instance_rmdir(const char *name)
> >>>>>  	}
> >>>>>  
> >>>>>  	tracing_set_nop(tr);
> >>>>> +	clear_ftrace_function_probes(tr);
> >>>>>  	event_trace_del_tracer(tr);
> >>>>>  	ftrace_clear_pids(tr);
> >>>>>  	ftrace_destroy_function_files(tr);
> >>>>> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> >>>>> index 291a1bca5748..98e0845f7235 100644
> >>>>> --- a/kernel/trace/trace.h
> >>>>> +++ b/kernel/trace/trace.h
> >>>>> @@ -980,6 +980,7 @@ register_ftrace_function_probe(char *glob, struct trace_array *tr,
> >>>>>  extern int
> >>>>>  unregister_ftrace_function_probe_func(char *glob, struct trace_array *tr,
> >>>>>  				      struct ftrace_probe_ops *ops);
> >>>>> +extern void clear_ftrace_function_probes(struct trace_array *tr);  
> >>>>
> >>>> This needs to have a stub function when CONFIG_DYNAMIC_FTRACE is not
> >>>> defined. Otherwise we have:
> >>>>
> >>>> kernel/trace/trace.c:7553:2: error: implicit declaration of function 'clear_ftrace_function_probes' [-Werror=implicit-function-declaration]
> >>>>   clear_ftrace_function_probes(tr);
> >>>>   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~  
> >>
> >> The prototype in trace.h is actually guarded by:
> >> #if defined(CONFIG_FUNCTION_TRACER) && defined(CONFIG_DYNAMIC_FTRACE)
> >>
> >> So, I will guard the call to clear_ftrace_function_probes() in trace.c 
> >> with the same.
> >>
> > 
> > No, the proper thing to do is to make a stub function in the else part
> > of the #if that the prototype was declared in.
> > 
> > static inline void clear_ftrace_function_probes(struct trace_array *tr)
> > {
> > }
> > 
> > Please, lets limit the #ifdef ugliness from the code.
> > 
> > -- Steve
> > 
> > 
> 
> 
> Hi Steve,
> 
> Are you good with this patch series. I am looking to see which
> of these should go into 4.13-rc1 - please ack individual patches
> that should be pulled into 4.13-rc1

Hi Shuah,
I see that Steven has already sent v2 of this series to Linus, including 
the selftest patches:
https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1399833.html
https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1399832.html

And I also noticed (after I came back from vacation) that Steven had 
fixed the #ifdef ugliness I had introduced..

Thanks,
Naveen