linux-kernel - Re: [PATCH v4 2/4] ftrace: Add support for function argument to graph tracer

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Message-ID: <c41e5ee7-18ba-40cf-8a31-19062d94f7b9@sirena.org.uk>
Date: Fri, 11 Apr 2025 14:00:40 +0100
From: Mark Brown <broonie@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
	bpf@...r.kernel.org, Masami Hiramatsu <mhiramat@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Sven Schnelle <svens@...ux.ibm.com>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>, Guo Ren <guoren@...nel.org>,
	Donglin Peng <dolinux.peng@...il.com>,
	Zheng Yejian <zhengyejian@...weicloud.com>, Aishwarya.TCV@....com
Subject: Re: [PATCH v4 2/4] ftrace: Add support for function argument to
 graph tracer

On Thu, Apr 10, 2025 at 01:17:45PM -0400, Steven Rostedt wrote:
> Mark Brown <broonie@...nel.org> wrote:

> > We've been seeing the PID filters selftest failing for a while on
> > several arm64 systems, a bisect I managed to run without running into
> > any confounding issues pointed to this patch which is in mainline as
> > ff5c9c576e75.  It's in the ftrace code, but I'm not immediately seeing
> > the relevance.  Output from a failing run:

> Hmm, I wonder if there's junk being added into the trace.

> Can you add this patch, and show me the output when it fails again?

# # + cat trace
# # # tracer: function_graph
# # #
# # # CPU  TASK/PID         DURATION                  FUNCTION CALLS
# # # |     |    |           |   |                     |   |   |   |
# # 0)  ftracet-5190  | ! 537.633 us  |  kernel_clone(); /* ret=0x1470 */
# # 
# # 0)  ftracet-5190  | ! 508.253 us  |  kernel_clone(); /* ret=0x1471 */
# # 
# # 0)  ftracet-5190  | ! 215.716 us  |  kernel_clone(); /* ret=0x1476 */
# # 
# # 0)  ftracet-5190  | ! 493.890 us  |  kernel_clone(); /* ret=0x147b */
# # 
# # + fail PID filtering not working?

...

# # + cat trace
# # # tracer: function_graph
# # #
# # # CPU  TASK/PID         DURATION                  FUNCTION CALLS
# # # |     |    |           |   |                     |   |   |   |
# # 0) ftracet-12279  | ! 598.118 us  |  kernel_clone(); /* ret=0x301f */
# # 
# # 0) ftracet-12279  | ! 492.539 us  |  kernel_clone(); /* ret=0x3020 */
# # 
# # 0) ftracet-12279  | ! 231.104 us  |  kernel_clone(); /* ret=0x3025 */
# # 
# # 0) ftracet-12279  | ! 555.566 us  |  kernel_clone(); /* ret=0x302a */
# # 
# # + fail PID filtering not working?

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