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Re: [PATCH v2 2.6.38-rc8-tip 17/20] 17: uprobes: filter chain
- From: Srikar Dronamraju <srikar at linux dot vnet dot ibm dot com>
- To: Stephen Wilson <wilsons at start dot ca>
- Cc: Peter Zijlstra <peterz at infradead dot org>, Ingo Molnar <mingo at elte dot hu>, Steven Rostedt <rostedt at goodmis dot org>, Linux-mm <linux-mm at kvack dot org>, Arnaldo Carvalho de Melo <acme at infradead dot org>, Linus Torvalds <torvalds at linux-foundation dot org>, Christoph Hellwig <hch at infradead dot org>, Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>, Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>, Oleg Nesterov <oleg at redhat dot com>, LKML <linux-kernel at vger dot kernel dot org>, SystemTap <systemtap at sources dot redhat dot com>, Jim Keniston <jkenisto at linux dot vnet dot ibm dot com>, Roland McGrath <roland at hack dot frob dot com>, Andi Kleen <andi at firstfloor dot org>, Andrew Morton <akpm at linux-foundation dot org>, "Paul E. McKenney" <paulmck at linux dot vnet dot ibm dot com>
- Date: Sat, 19 Mar 2011 00:46:48 +0530
- Subject: Re: [PATCH v2 2.6.38-rc8-tip 17/20] 17: uprobes: filter chain
- References: <20110314133403.27435.7901.sendpatchset@localhost6.localdomain6> <20110314133722.27435.55663.sendpatchset@localhost6.localdomain6> <20110315194914.GA24972@fibrous.localdomain>
- Reply-to: Srikar Dronamraju <srikar at linux dot vnet dot ibm dot com>
* Stephen Wilson <wilsons@start.ca> [2011-03-15 15:49:14]:
>
>
>
> On Mon, Mar 14, 2011 at 07:07:22PM +0530, Srikar Dronamraju wrote:
> >
> > Loops through the filters callbacks of currently registered
> > consumers to see if any consumer is interested in tracing this task.
>
> Should this be part of the series? It is not currently used.
>
> > /* Acquires uprobe->consumer_rwsem */
> > +static bool filter_chain(struct uprobe *uprobe, struct task_struct *t)
> > +{
> > + struct uprobe_consumer *consumer;
> > + bool ret = false;
> > +
> > + down_read(&uprobe->consumer_rwsem);
> > + 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.
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.
--
Thanks and Regards
Srikar