From: Matthew Auld <matthew.william.auld@gmail.com>
To: George Spelvin <lkml@sdf.org>
Cc: Intel Graphics Development <intel-gfx@lists.freedesktop.org>,
Matthew Auld <matthew.auld@intel.com>
Subject: Re: [Intel-gfx] [PATCH] drivers/gpu/drm/i915/selftests/i915_buddy.c: Fix bug
Date: Thu, 26 Mar 2020 17:04:43 +0000 [thread overview]
Message-ID: <CAM0jSHNGok83kk1Z7vm4rKJw3O1uC=9czSuNfidW6wb900HppQ@mail.gmail.com> (raw)
In-Reply-To: <20200325192429.GA8865@SDF.ORG>
On Wed, 25 Mar 2020 at 21:23, George Spelvin <lkml@sdf.org> wrote:
>
> igt_mm_config() calls ilog2() on the (pseudo)random 21-bit number
> s>>12. Once in 2 million seeds, this is zero and ilog2 summons
> the nasal demons.
>
> There was an attempt to handle this case with a max(), but that's
> too late; ms could already be something bizarre.
>
> Given that the low 12 bits of s and ms are always zero, it's a lot
> simpler just to divide them by 4096, then everything fits into 32
> bits, and we can easily generate a random number 1 <= s <= 0x1fffff.
>
> Signed-off-by: George Spelvin <lkml@sdf.org>
> Fixes: 14d1b9a6247c
> Cc: Matthew Auld <matthew.auld@intel.com>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: intel-gfx@lists.freedesktop.org
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
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next prev parent reply other threads:[~2020-03-26 17:05 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-25 19:24 [Intel-gfx] [PATCH] drivers/gpu/drm/i915/selftests/i915_buddy.c: Fix bug George Spelvin
2020-03-25 23:09 ` [Intel-gfx] ✗ Fi.CI.CHECKPATCH: warning for " Patchwork
2020-03-25 23:35 ` [Intel-gfx] ✓ Fi.CI.BAT: success " Patchwork
2020-03-26 3:44 ` [Intel-gfx] ✗ Fi.CI.IGT: failure " Patchwork
2020-03-26 17:04 ` Matthew Auld [this message]
2020-03-26 20:21 ` [Intel-gfx] [PATCH] " George Spelvin
2020-03-27 10:45 ` Matthew Auld
2020-08-06 16:02 ` Chris Wilson
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