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From: Jeremy Fertic <jeremyfertic@gmail.com>
To: Stefan Agner <stefan@agner.ch>
Cc: linux-arm-kernel@lists.infradead.org, rostedt@goodmis.org,
	Russell King <linux@armlinux.org.uk>,
	Arnd Bergmann <arnd@arndb.de>,
	linux-kernel@vger.kernel.org
Subject: ARM: config issue with ftrace function graph tracer
Date: Fri, 11 Jan 2019 18:01:39 -0700	[thread overview]
Message-ID: <20190112010139.GA5288@r2700x.localdomain> (raw)

I'm having a problem with the ftrace function graph tracer on a 32 bit arm
board (orangepi pc). A bisect points to the following commit:

f9b58e8c7d03 ("ARM: 8800/1: use choice for kernel unwinders")

Before this commit, if I use sunxi_defconfig and then menuconfig to enable
FTRACE and FUNCTION_TRACER then the function graph tracer works. With this
commit, and as of v5.0-rc1, doing the same as above results in a broken
function graph tracer and often an oops as well. The commit introduces a
choice group and it looks like it should default to UNWINDER_FRAME_POINTER
if FUNCTION_GRAPH_TRACER is enabled. FUNCTION_GRAPH_TRACER is enabled by
default when I enable FUNCTION_TRACER but this has no effect on the choice.
The choice always defaults to the other option which is UNWINDER_ARM. If I
manually choose UNWINDER_FRAME_POINTER then the function graph tracer works
fine.

Any idea why the default behaviour has changed?

Thanks,
Jeremy

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             reply	other threads:[~2019-01-12  1:02 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-12  1:01 Jeremy Fertic [this message]
2019-01-13 15:41 ` ARM: config issue with ftrace function graph tracer Stefan Agner
2019-01-13 16:14   ` Russell King - ARM Linux
2019-01-15 22:37     ` Stefan Agner

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