linux-kernel - RE: ftrace not showing the process names for all processes on syscall events

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Date:   Wed, 1 Apr 2020 14:37:28 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Steven Rostedt' <rostedt@...dmis.org>
CC:     'Linux Kernel Mailing List' <linux-kernel@...r.kernel.org>
Subject: RE: ftrace not showing the process names for all processes on syscall
 events

From: David Laight
> Sent: 30 March 2020 19:15
> From: Steven Rostedt
> > Sent: 30 March 2020 19:08
> > On Mon, 30 Mar 2020 15:34:08 +0000
> > David Laight <David.Laight@...LAB.COM> wrote:
> >
> > > Oh, does the 'function_graph' code ignore tail calls?
> >
> > Yes and no ;-)  It works by dumb luck. As it was a year after function
> > graph tracing was live (some time in 2010 I believe) that someone brought
> > up tail calls, and I had to take a look at how it never crashed, and was
> > surprised that it "just worked". Here's a summary:
> 
> 'Dumb luck' seems to be failing me :-)
> I'll look more closely tomorrow.

The 'problem' is that some files like lib/iov_iter.c don't have the
tracepoints compiled in.

So calls I was expecting to see were absent.

	David

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