linux-kernel - Re: [PATCH v5 2/5] lib/test_bitmap: add tests for bitmap

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Date:   Mon, 25 Sep 2023 15:23:11 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Alexander Potapenko <glider@...gle.com>
Cc:     catalin.marinas@....com, will@...nel.org, pcc@...gle.com,
        andreyknvl@...il.com, linux@...musvillemoes.dk,
        yury.norov@...il.com, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, eugenis@...gle.com,
        syednwaris@...il.com, william.gray@...aro.org
Subject: Re: [PATCH v5 2/5] lib/test_bitmap: add tests for
 bitmap_{read,write}()

On Mon, Sep 25, 2023 at 02:16:37PM +0200, Alexander Potapenko wrote:

...

> > +/*
> > + * Test bitmap should be big enough to include the cases when start is not in
> > + * the first word, and start+nbits lands in the following word.
> > + */
> > +#define TEST_BIT_LEN (1000)
> 
> Dunno why this didn't fire previously, but CONFIG_CPU_BIG_ENDIAN=y
> kernel reports mismatches here, presumably because the last quad word
> ends up partially initialized.

Hmm... But if designed and used correctly it shouldn't be the issue,
and 1000, I believe, is carefully chosen to be specifically not dividable
by pow-of-2 value.

> The easiest fix is to make TEST_BIT_LEN divisible by 64 (e.g. 1024)

Wouldn't it hide the real issue somewhere?

-- 
With Best Regards,
Andy Shevchenko