Re: [PATCH] tracing: Export key trace event symbols

From: Pawel Moll <pawel.moll@arm.com>
To: David Ahern <dsahern@gmail.com>
Cc: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ron Rechenmacher <ron@fnal.gov>,
	Christoph Hellwig <hch@infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Arjan van de Ven <arjan@linux.intel.com>,
	Namhyung Kim <namhyung@kernel.org>,
	Stephane Eranian <eranian@google.com>
Subject: Re: [PATCH] tracing: Export key trace event symbols
Date: Thu, 23 Apr 2015 16:33:42 +0100	[thread overview]
Message-ID: <1429803222.3242.24.camel@arm.com> (raw)
In-Reply-To: <1429802909.3242.23.camel@arm.com>

On Thu, 2015-04-23 at 16:28 +0100, Pawel Moll wrote:
> On Wed, 2015-04-22 at 16:36 +0100, David Ahern wrote:
> > On 4/22/15 8:47 AM, Arnaldo Carvalho de Melo wrote:
> > > Em Wed, Apr 22, 2015 at 08:53:14AM -0400, Steven Rostedt escreveu:
> > >> >On Tue, 21 Apr 2015 21:24:51 -0500
> > >> >Ron Rechenmacher<ron@fnal.gov>  wrote:
> > >>> > >I've looked at the above reference briefly and it appears that user-space
> > >>> > >would be mmapping the buffer read-only. Is that correct?
> > >> >
> > >> >Correct, but I'm sure we could still add something (if it doesn't
> > >> >already exist) to have userspace write into the buffer. Ftrace has that
> > >> >with the trace_marker file.
> > > There is something in the works, I guess Pawell Moll (sp) was working on it, and
> > > David Ahern (CCed) should know, David?
> > >
> > 
> > I played around with generating perf events in userspace with the 
> > intention of having the userspace events get merged with kernel events 
> > during the processing stage, but I did not take it to the point of 
> > integrating into perf. This was around October 2013. I got distracted 
> > with other topics and have not come back to it.
> > 
> > Pawel has a patch that allows userspace to inject events into the stream 
> > via ioctl calls.
> 
> In the last version it was even a prctl - no need for a perf file
> descriptor any more :-)
> 
> But the patch requires more care if it's to go in, so I'm open to people
> screaming "yes, we need it!" ;-)

Forgot to quote the link:

http://article.gmane.org/gmane.linux.kernel.api/5851

Pawel