Re: [PATCH] clk: vt8500: don't return possibly uninitialized data

From	Arnd Bergmann <arnd@arndb.de>
Newsgroups	linux.kernel
Subject	Re: [PATCH] clk: vt8500: don't return possibly uninitialized data
Date	2016-02-03 10:20 +0100
Message-ID	<qY1Lr-8sb-7@gated-at.bofh.it> (permalink)
References	<qXjU6-19m-11@gated-at.bofh.it> <qXPqV-8iU-1@gated-at.bofh.it> <qY18K-7WJ-19@gated-at.bofh.it>
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On Wednesday 03 February 2016 11:36:26 Roman Volkov wrote:
> 
> Hi Arnd,
> 
> Thanks for fixing this code! Did someone reproduce this bug, or this
> is something theoretical, based on the code analysis? I just never
> heard about the issue. I can look into the code on the weekends too, I
> have WM8505\WM8650 machines to test.

I only fixed it after analysing the gcc warnings I got after Andrzej Hajda's
patch, and he also did it to fix the initial problem he found using
coccinelle, so I don't think anyone has run into the problem on live
hardware.

As long as all drivers ask for clock rates that are valid, you won't
see either problem.

> Is it enough to run the regular kernel build for WM8650 to see the
> warnings, or there are special options in the kernel to run the compiler
> test?

The warning is hidden if you build with -Os (CONFIG_CC_OPTIMIZE_FOR_SIZE),
and it may not happen with all gcc versions. I was using gcc-5.2.

	Arnd

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Thread

[PATCH] clk: vt8500: don't return possibly uninitialized data Arnd Bergmann <arnd@arndb.de> - 2016-02-01 11:30 +0100
  Re: [PATCH] clk: vt8500: don't return possibly uninitialized data Stephen Boyd <sboyd@codeaurora.org> - 2016-02-02 02:20 +0100
    Re: [PATCH] clk: vt8500: don't return possibly uninitialized data Arnd Bergmann <arnd@arndb.de> - 2016-02-02 14:00 +0100
      Re: [PATCH] clk: vt8500: don't return possibly uninitialized data Stephen Boyd <sboyd@codeaurora.org> - 2016-02-02 20:50 +0100
        Re: [PATCH] clk: vt8500: don't return possibly uninitialized data Arnd Bergmann <arnd@arndb.de> - 2016-02-02 21:10 +0100
          Re: [PATCH] clk: vt8500: don't return possibly uninitialized data Roman Volkov <v1ron@mail.ru> - 2016-02-03 09:40 +0100
            Re: [PATCH] clk: vt8500: don't return possibly uninitialized data Arnd Bergmann <arnd@arndb.de> - 2016-02-03 10:20 +0100

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