linux-kernel - Re: [PATCH][next] drm/i915/selftests: fix uninitialized variable sum when summing up values

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Date:   Tue, 10 Dec 2019 14:34:48 +0000
From:   Chris Wilson <chris@...is-wilson.co.uk>
To:     Colin King <colin.king@...onical.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Matthew Auld <matthew.auld@...el.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        dri-devel@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] drm/i915/selftests: fix uninitialized variable sum when
 summing up values

Quoting Colin King (2019-12-10 14:32:05)
> From: Colin Ian King <colin.king@...onical.com>
> 
> Currently the variable sum is not uninitialized and hence will cause an
> incorrect result in the summation values.  Fix this by initializing
> sum to the first item in the summation.
> 
> Addresses-Coverity: ("Uninitialized scalar variable")
> Fixes: 3c7a44bbbfa7 ("drm/i915/selftests: Perform some basic cycle counting of MI ops")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  drivers/gpu/drm/i915/gt/selftest_engine_cs.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/selftest_engine_cs.c b/drivers/gpu/drm/i915/gt/selftest_engine_cs.c
> index 761d81f4bd68..f88e445a1cae 100644
> --- a/drivers/gpu/drm/i915/gt/selftest_engine_cs.c
> +++ b/drivers/gpu/drm/i915/gt/selftest_engine_cs.c
> @@ -108,7 +108,7 @@ static u32 trifilter(u32 *a)
>  
>         sort(a, COUNT, sizeof(*a), cmp_u32, NULL);
>  
> -       sum += mul_u32_u32(a[2], 2);
> +       sum = mul_u32_u32(a[2], 2);

/o\
Reviewed-by: Chris Wilson <chris@...is-wilson.co.uk>
-Chris