Re: [PATCH -tip 02/13] [CLEANUP]tracing/kprobes: merge trace probe enable/disable functions

[Steven Rostedt <rostedt@goodmis.org>]

On Mon, 2011-06-27 at 16:26 +0900, Masami Hiramatsu wrote:
> Merge redundant enable/disable functions into enable_trace_probe()
> and disable_trace_probe().
> 
> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Frederic Weisbecker <fweisbec@gmail.com>
> Cc: Ingo Molnar <mingo@redhat.com>
> ---
> 
>  kernel/trace/trace_kprobe.c |   88 +++++++++++++++++--------------------------
>  1 files changed, 34 insertions(+), 54 deletions(-)
> 
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index bad87e9..ce5e6aa 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -683,6 +683,34 @@ static struct trace_probe *find_trace_probe(const char *event,
>  	return NULL;
>  }
>  
> +/* Enable trace_probe - @flag must be TP_FLAG_TRACE or TP_FLAG_PROFILE */
> +static int enable_trace_probe(struct trace_probe *tp, int flag)
> +{
> +	int ret = 0;
> +
> +	tp->flags |= flag;
> +	if (tp->flags & (TP_FLAG_TRACE | TP_FLAG_PROFILE)) {
> +		if (trace_probe_is_return(tp))
> +			ret = enable_kretprobe(&tp->rp);
> +		else
> +			ret = enable_kprobe(&tp->rp.kp);
> +	}

Hmm, this seems weird. Should we have any protection here? I mean, is it
ok to call the enable_kprobe() twice? Or should we have something like:

{
	int old_flags = tp->flags;
	int ret = 0;

	tp->flags |= flag;

	if (!(old_flags & (TP_FLAG_TRACE | TP_FLAG_PROFILE)) &&
	    flag & (TP_FLAG_TRACE | TP_FLAG_PROFILE)) {
		[...]
	}

	return ret;
}


> +
> +	return ret;
> +}
> +
> +/* Disable trace_probe - @flag must be TP_FLAG_TRACE or TP_FLAG_PROFILE */
> +static void disable_trace_probe(struct trace_probe *tp, int flag)
> +{
> +	tp->flags &= ~flag;
> +	if (!(tp->flags & (TP_FLAG_TRACE | TP_FLAG_PROFILE))) {
> +		if (trace_probe_is_return(tp))
> +			disable_kretprobe(&tp->rp);
> +		else
> +			disable_kprobe(&tp->rp.kp);
> +	}
> +}

Same here.

Or do we want to reenable or re disable the probe?

-- Steve

> +
>  /* Unregister a trace_probe and probe_event: call with locking probe_lock */
>  static void unregister_trace_probe(struct trace_probe *tp)
>  {
> @@ -1512,30 +1540,6 @@ partial:
>  	return TRACE_TYPE_PARTIAL_LINE;
>  }
>  
> -static int probe_event_enable(struct ftrace_event_call *call)
> -{
> -	struct trace_probe *tp = (struct trace_probe *)call->data;
> -
> -	tp->flags |= TP_FLAG_TRACE;
> -	if (trace_probe_is_return(tp))
> -		return enable_kretprobe(&tp->rp);
> -	else
> -		return enable_kprobe(&tp->rp.kp);
> -}
> -
> -static void probe_event_disable(struct ftrace_event_call *call)
> -{
> -	struct trace_probe *tp = (struct trace_probe *)call->data;
> -
> -	tp->flags &= ~TP_FLAG_TRACE;
> -	if (!(tp->flags & (TP_FLAG_TRACE | TP_FLAG_PROFILE))) {
> -		if (trace_probe_is_return(tp))
> -			disable_kretprobe(&tp->rp);
> -		else
> -			disable_kprobe(&tp->rp.kp);
> -	}
> -}
> -
>  #undef DEFINE_FIELD
>  #define DEFINE_FIELD(type, item, name, is_signed)			\
>  	do {								\
> @@ -1714,49 +1718,25 @@ static __kprobes void kretprobe_perf_func(struct kretprobe_instance *ri,
>  	head = this_cpu_ptr(call->perf_events);
>  	perf_trace_buf_submit(entry, size, rctx, entry->ret_ip, 1, regs, head);
>  }
> -
> -static int probe_perf_enable(struct ftrace_event_call *call)
> -{
> -	struct trace_probe *tp = (struct trace_probe *)call->data;
> -
> -	tp->flags |= TP_FLAG_PROFILE;
> -
> -	if (trace_probe_is_return(tp))
> -		return enable_kretprobe(&tp->rp);
> -	else
> -		return enable_kprobe(&tp->rp.kp);
> -}
> -
> -static void probe_perf_disable(struct ftrace_event_call *call)
> -{
> -	struct trace_probe *tp = (struct trace_probe *)call->data;
> -
> -	tp->flags &= ~TP_FLAG_PROFILE;
> -
> -	if (!(tp->flags & TP_FLAG_TRACE)) {
> -		if (trace_probe_is_return(tp))
> -			disable_kretprobe(&tp->rp);
> -		else
> -			disable_kprobe(&tp->rp.kp);
> -	}
> -}
>  #endif	/* CONFIG_PERF_EVENTS */
>  
>  static __kprobes
>  int kprobe_register(struct ftrace_event_call *event, enum trace_reg type)
>  {
> +	struct trace_probe *tp = (struct trace_probe *)event->data;
> +
>  	switch (type) {
>  	case TRACE_REG_REGISTER:
> -		return probe_event_enable(event);
> +		return enable_trace_probe(tp, TP_FLAG_TRACE);
>  	case TRACE_REG_UNREGISTER:
> -		probe_event_disable(event);
> +		disable_trace_probe(tp, TP_FLAG_TRACE);
>  		return 0;
>  
>  #ifdef CONFIG_PERF_EVENTS
>  	case TRACE_REG_PERF_REGISTER:
> -		return probe_perf_enable(event);
> +		return enable_trace_probe(tp, TP_FLAG_PROFILE);
>  	case TRACE_REG_PERF_UNREGISTER:
> -		probe_perf_disable(event);
> +		disable_trace_probe(tp, TP_FLAG_PROFILE);
>  		return 0;
>  #endif
>  	}