linux-kernel - Re: [PATCH] tracing/kprobes: Add trace event trigger invocations

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Date:	Mon, 06 Jan 2014 13:44:00 -0600
From:	Tom Zanussi <tom.zanussi@...ux.intel.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Jean-Jacques Hiblot <jjhiblot@...phandler.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tracing/kprobes: Add trace event trigger invocations

On Mon, 2014-01-06 at 11:10 -0500, Steven Rostedt wrote:
> On Sat, 28 Dec 2013 20:24:08 -0600
> Tom Zanussi <tom.zanussi@...ux.intel.com> wrote:
> 
> > Add code to the kprobe/kretprobe event functions that will invoke any
> > event triggers associated with a probe's ftrace_event_file.
> > 
> > The code to do this is very similar to the invocation code already
> > used to invoke the triggers associated with static events and
> > essentially replaces the existing soft-disable checks with a superset
> > that preserves the original behavior but adds the bits needed to
> > support event triggers.
> > 
> > Signed-off-by: Tom Zanussi <tom.zanussi@...ux.intel.com>
> > ---
> >  kernel/trace/trace_kprobe.c | 42 ++++++++++++++++++++++++++++++++++++------
> >  1 file changed, 36 insertions(+), 6 deletions(-)
> > 
> > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> > index dae9541..1ee13eb 100644
> > --- a/kernel/trace/trace_kprobe.c
> > +++ b/kernel/trace/trace_kprobe.c
> > @@ -812,12 +812,20 @@ __kprobe_trace_func(struct trace_probe *tp, struct pt_regs *regs,
> >  	struct ring_buffer *buffer;
> >  	int size, dsize, pc;
> >  	unsigned long irq_flags;
> > +	unsigned long eflags;
> > +	enum event_trigger_type __tt = ETT_NONE;
> 
> What's the significance of the "__" in the variable?
> 
> Looks as if you copied it from the ftrace_raw_event_* macro. The "__"
> there is usually recommended because it is a macro and we try to avoid
> namespace collisions by adding the "__".
> 
> This is a proper function, please remove the "__" from it.
> 

Right, it was just for consistency with the other invocations.  Updates
to this and the syscall invocations which also do the same thing, coming
up...

Tom

> Thanks,
> 
> -- Steve
> 
> 
> >  	struct ftrace_event_call *call = &tp->call;
> >  
> >  	WARN_ON(call != ftrace_file->event_call);
> >  
> > -	if (test_bit(FTRACE_EVENT_FL_SOFT_DISABLED_BIT, &ftrace_file->flags))
> > -		return;
> > +	eflags = ftrace_file->flags;
> > +
> > +	if (!(eflags & FTRACE_EVENT_FL_TRIGGER_COND)) {
> > +		if (eflags & FTRACE_EVENT_FL_TRIGGER_MODE)
> > +			event_triggers_call(ftrace_file, NULL);
> > +		if (eflags & FTRACE_EVENT_FL_SOFT_DISABLED)
> > +			return;
> > +	}
> >  
> >  	local_save_flags(irq_flags);
> >  	pc = preempt_count();


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