linux-kernel - Re: [for-next][PATCH 08/20] tracing: Warn if a tracepoint is not set via debugfs

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Message-ID: <20140311104602.151bfdb3@gandalf.local.home>
Date:	Tue, 11 Mar 2014 10:46:02 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc:	"Frank Ch. Eigler" <fche@...hat.com>, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...nel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Berg <johannes.berg@...el.com>
Subject: Re: [for-next][PATCH 08/20] tracing: Warn if a tracepoint is not
 set via debugfs

On Tue, 11 Mar 2014 04:08:27 +0000 (UTC)
Mathieu Desnoyers <mathieu.desnoyers@...icios.com> wrote:

 
> > That's my argument.
> 
> So basically, all we'd have to do in LTTng is to add a hash table tracking the
> tracepoint probes which are registered, but for which there are no
> tracepoint call sites. Whenever registration of a probe would fail due to
> -ENODEV (assuming we unregister the probe within tracepoint.c when we return
> -ENODEV, as you initially proposed), we would put this probe in the hash table.
> Upon module coming, we would iterate on the module's tracepoints and check
> if any of those match the content of the hash table, and then register the
> probe.
> 
> I guess I'd prefer that to the weird successful failure return value in
> tracepoint.c.
> 

OK, then I'll add back in the removal of the tracepoint on this error.
Then your LTTng module can handle the tracepoints that don't exist yet.

-- Steve
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