linux-kernel - Re: [PATCH v3 2/2] lib: make a test module with set/clear bit

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Date:   Fri, 21 Feb 2020 15:16:11 -0800
From:   Jesse Brandeburg <jesse.brandeburg@...el.com>
To:     Andy Shevchenko <andriy.shevchenko@...el.com>
Cc:     <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
        <x86@...nel.org>, <linux-kernel@...r.kernel.org>,
        <linux@...musvillemoes.dk>, <dan.j.williams@...el.com>,
        <peterz@...radead.org>
Subject: Re: [PATCH v3 2/2] lib: make a test module with set/clear bit

On Fri, 21 Feb 2020 12:25:18 +0200 Andy wrote:
> On Thu, Feb 20, 2020 at 03:21:55PM -0800, Jesse Brandeburg wrote:
> > Test some bit clears/sets to make sure assembly doesn't change, and
> > that the set_bit and clear_bit functions work and don't cause sparse
> > warnings.
> > 
> > Instruct Kbuild to build this file with extra warning level -Wextra,
> > to catch new issues, and also doesn't hurt to build with C=1.
> > 
> > This was used to test changes to arch/x86/include/asm/bitops.h.
> > 
> > In particular, sparse (C=1) was very concerned when the last bit
> > before a natural boundary, like 7, or 31, was being tested, as this
> > causes sign extension (0xffffff7f) for instance when clearing bit 7.
> > 
> > Recommended usage:
> > make defconfig
> > scripts/config -m CONFIG_TEST_BITOPS
> > make modules_prepare
> > make C=1 W=1 lib/test_bitops.ko
> > objdump -S -d lib/test_bitops.ko  
> 
> Thanks!
> One comments below, after addressing:
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@...el.com>

Thanks!

> 	BITOPS_LAST = 255,
> 	BITOPS_LENGTH = 256
> 
> and...
> 
> static DECLARE_BITMAP(g_bitmap, BITOPS_LENGTH);

Fixed in v4