linux-kernel - Re: [PATCH 3/6] uprobes/tracing: Make uprobe_{trace,perf}

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Date:	Sat, 13 Apr 2013 15:01:44 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Anton Arapov <anton@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/6] uprobes/tracing: Make uprobe_{trace,perf}_print()
 uretprobe-friendly

* Oleg Nesterov <oleg@...hat.com> [2013-04-09 15:33:33]:

> On 04/07, Srikar Dronamraju wrote:
> >
> > * Oleg Nesterov <oleg@...hat.com> [2013-04-01 18:08:51]:
> >
> > > diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
> > > index e91a354..db2718a 100644
> > > --- a/kernel/trace/trace_uprobe.c
> > > +++ b/kernel/trace/trace_uprobe.c
> > > @@ -515,15 +515,26 @@ static void uprobe_trace_print(struct trace_uprobe *tu,
> > >  	int size, i;
> > >  	struct ftrace_event_call *call = &tu->call;
> > >
> > > -	size = SIZEOF_TRACE_ENTRY(1) + tu->size;
> > > +	if (is_ret_probe(tu))
> >
> > One nit:
> > Here and couple of places below .. we could check for func instead of
> > is_ret_probe() right?
> 
> Yes we could. And note that we do not really need both uprobe_trace_func()
> and uretprobe_perf_func(), we could use a single function and check "func".
> 
> But:
> 
> > Or is there an advantage of checking is_ret_probe() over func?
> 
> I believe yes. Firstly, we can't use 0ul as "invalid func address" to detect
> the !is_ret_probe() case, we need, say, -1ul which probably needs a symbolic
> name. In fact, I'd prefer to add another "is_return" argument if we want to
> avoid is_ret_probe() and unify 2 functions.
> 
> But more importantly, I think that is_ret_probe() is much more grep-friendly
> and thus more understandable and consistent with other checks which can not
> rely on "func".

Okay, Agree. 


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