linux-kernel - Re: [PATCH v2 2.6.38-rc8-tip 17/20] 17: uprobes: filter chain

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Message-ID: <20110318221042.GA3586@fibrous.localdomain>
Date:	Fri, 18 Mar 2011 18:10:42 -0400
From:	Stephen Wilson <wilsons@...rt.ca>
To:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	Steven Rostedt <rostedt@...dmis.org>,
	Linux-mm <linux-mm@...ck.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Christoph Hellwig <hch@...radead.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Oleg Nesterov <oleg@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	SystemTap <systemtap@...rces.redhat.com>,
	Jim Keniston <jkenisto@...ux.vnet.ibm.com>,
	Roland McGrath <roland@...k.frob.com>,
	Andi Kleen <andi@...stfloor.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [PATCH v2 2.6.38-rc8-tip 17/20] 17: uprobes: filter chain


On Sat, Mar 19, 2011 at 12:46:48AM +0530, Srikar Dronamraju wrote:
> > > +	for (consumer = uprobe->consumers; consumer;
> > > +					consumer = consumer->next) {
> > > +		if (!consumer->filter || consumer->filter(consumer, t)) {
> > 
> > The implementation does not seem to match the changelog description.
> > Should this not be:
> > 
> >                 if (consumer->filter && consumer->filter(consumer, t))
> > 
> >   ?
> 
> filter is optional; if filter is present, then it means that the
> tracer is interested in a specific set of processes that maps this
> inode. If there is no filter; it means that it is interested in all
> processes that map this filter. 

Ah OK.  That does make sense then.  Thanks!


> filter_chain() should return true if any consumer is interested in
> tracing this task.  if there is a consumer who hasnt defined a filter
> then we dont need to loop thro remaining consumers.
> 
> Hence 
> 
> if (!consumer->filter || consumer->filter(consumer, t)) {
>  
> seems better suited to me.

-- 
steve

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