Re: test_bitmap fails on ppc/ppc64 on kernels v7.1.3, v7.2-rc2
From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Date: 2026-07-08 10:52:37
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On Wed, Jul 08, 2026 at 09:51:34AM +0200, Christophe Leroy (CS GROUP) wrote:
Le 08/07/2026 à 09:43, Andy Shevchenko a écrit :quoted
On Wed, Jul 08, 2026 at 01:25:01AM +0200, Erhard Furtner wrote:
...
quoted
Oh, this is nice. So, there are two (more?) options I see to mitigate the issue: - carefully copy the garbage from the stack to the expected values (effectively merge the whatever is on stack with the expected value) - allocate buffers on heap The latter seems the easiest and right thing to do (since we can't really predict if the stack pattern is the same or bitmap APIs scatters the bits just on top of the respective set or clear ones over that pattern). I will send a patch, thanks for the report and analysis!The following change fixes the issue for me:
Indeed, I missed that and before seeing this message I also realised that this is the probably best fix. Can you submit it as a formal patch, please?
quoted hunk ↗ jump to hunk
diff --git a/lib/test_bitmap.c b/lib/test_bitmap.c index 69813c10e6c0b..448c3eb48a4a8 100644 --- a/lib/test_bitmap.c +++ b/lib/test_bitmap.c@@ -392,6 +392,7 @@ static void __init test_bitmap_sg(void) /* Scatter/gather relationship */ bitmap_zero(bmap_tmp, 100); + bitmap_zero(bmap_res, 100); bitmap_gather(bmap_tmp, bmap_scatter, sg_mask, nbits); bitmap_scatter(bmap_res, bmap_tmp, sg_mask, nbits); expect_eq_bitmap(bmap_scatter, bmap_res, 100);
-- With Best Regards, Andy Shevchenko