linux-kernel - Re: [PATCH 2/5] tools lib traceevent: handle the '->' operator

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Message-ID: <20140318111523.750c34a0@gandalf.local.home>
Date:	Tue, 18 Mar 2014 11:15:23 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	Ramkumar Ramachandra <artagnon@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Jiri Olsa <jolsa@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Ben Widawsky <ben@...dawsk.net>,
	Chris Wilson <chris@...is-wilson.co.uk>,
	Daniel Vetter <daniel.vetter@...ll.ch>
Subject: Re: [PATCH 2/5] tools lib traceevent: handle the '->' operator

On Tue, 18 Mar 2014 23:18:24 +0900
Namhyung Kim <namhyung@...nel.org> wrote:

> Hi Ramkumar,
> 
> On Tue, Mar 18, 2014 at 11:12 PM, Ramkumar Ramachandra
> <artagnon@...il.com> wrote:
> > Hi Namhyung,
> >
> > On Tue, Mar 18, 2014 at 3:58 AM, Namhyung Kim <namhyung@...nel.org> wrote:
> >> Hmm.. AFAIK we don't support the '->' operator so I think it's an error
> >> in the callsite.  Where do you see the message though?  I couldn't find
> >> it on my setup.
> >>
> >> I'd also like to add following patch to see the location of parse
> >> failure easily.
> >
> > I applied your patch and ran 'perf test'. I get:
> >
> >   Warning: [i915:i915_gem_evict_vm] unknown op '->'
> >
> > So, where should we dig to find this callsite?
> 
> /sys/kernel/debug/tracing/events/i915/i915_gen_evict_vm/format :)
> 

Actually, that's a bug in the kernel. You should *NEVER* redirect from
the ring buffer. There's no guarantee that the data still exists and
this can cause a kernel oops.

-- Steve
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