linux-kernel - Re: WARNING in tracepoint_probe_register

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Message-ID: <20180315083125.GU4064@hirez.programming.kicks-ass.net>
Date:   Thu, 15 Mar 2018 09:31:25 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        syzbot <syzbot+9c0d616860575a73166a@...kaller.appspotmail.com>,
        Ingo Molnar <mingo@...hat.com>, acme <acme@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        syzkaller-bugs@...glegroups.com,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>
Subject: Re: WARNING in tracepoint_probe_register_prio (2)

On Wed, Mar 14, 2018 at 05:37:46PM -0400, Steven Rostedt wrote:
> On Tue, 13 Mar 2018 11:29:51 -0400 (EDT)
> Mathieu Desnoyers <mathieu.desnoyers@...icios.com> wrote:
> 
> > Here is a WARN_ON() splat in tracepoint.c, which I suspect is caused
> > by perf trying to register the same probe twice to the tracepoint API.
> > We got another splat on unregister too, which I will forward in a
> > separate email.
> > 
> > Thoughts ?
> 
> Yes, it looks like it's perf not accounting for registered events
> properly.
> 
> Peter?

I've not yet managed to reproduce, but if you look at the provided
repro.c file, you'll see it opens two _different_ events.