linux-kernel - Re: [PATCH 0/7] tracing: bug fixes for tracing/filters

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Message-ID: <20090412100205.GA3023@elte.hu>
Date:	Sun, 12 Apr 2009 12:02:05 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Tom Zanussi <tzanussi@...il.com>, Li Zefan <lizf@...fujitsu.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>, paulmck@...ux.vnet.ibm.com
Subject: Re: [PATCH 0/7] tracing: bug fixes for tracing/filters


* Frederic Weisbecker <fweisbec@...il.com> wrote:

> On Sat, Apr 11, 2009 at 04:30:48AM -0500, Tom Zanussi wrote:
> > Hi,
> > 
> > On Sat, 2009-04-11 at 15:52 +0800, Li Zefan wrote:
> > > This patchset fixes some bugs in tracing/filters. Most of the change
> > > goes to the last patch, and others are small ones.
> > > 
> > 
> > At first glance, they look good and fix real problems - thanks for
> > fixing them.  Re patch 7, there's been some discussion about using rcu
> > for this.  See:
> > 
> > http://lkml.org/lkml/2009/4/5/46
> > 
> > >From that discussion, it seems some non-trivial changes to rcu would be
> > needed for this.  I'm playing around with a different idea now to
> > hopefully avoid the need for that, or the other approach mentioned, of
> > temporarily stopping tracing while removing/changing the filters.
> > 
> > Basically my thought is to avoid the problem by not allocating or
> > destroying the preds when removing filters but instead switch out the
> > pred->fns with a nop version while keeping the fields intact for awhile.
> > I think that will work for removing filters, but I still need to think
> > about how it would (or would not) work for replacing them.
> >  
> > Tom
> 
> 
> 
> It would be sort of reinventing rcu :-)
>
> Well, Paul proposed something recently, hmm I should 
> double check this discussion.
> 
> Anyway, the fixes from Li (other than 4 and 7 for which we 
> have comments) look very good!

Ok, i've applied 1,2,3,6 to tip/tracing/urgent (most of them 
are fixes needed for current mainline).

5 had dependency on 4 which is being discussed. 7 is being 
discussed as well, with Tom having promised a patch.

Thanks,

	Ingo
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