The patch titled
Subject: lib/find_bit_benchmark.c: avoid soft lockup in test_find_first_bit()
has been added to the -mm tree. Its filename is
lib-avoid-soft-lockup-in-test_find_first_bit.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/lib-avoid-soft-lockup-in-test_find_first_bit.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/lib-avoid-soft-lockup-in-test_find_first_bit.patch
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------------------------------------------------------
From: Yury Norov <ynorov@xxxxxxxxxxxxxxxxxx>
Subject: lib/find_bit_benchmark.c: avoid soft lockup in test_find_first_bit()
test_find_first_bit() is intentionally sub-optimal, and may cause soft
lockup due to long time of run on some systems. So decrease length of
bitmap to traverse to avoid lockup.
With the change below, time of test execution doesn't exceed 0.2 seconds
on my testing system.
Link: http://lkml.kernel.org/r/20180420171949.15710-1-ynorov@xxxxxxxxxxxxxxxxxx
Fixes: 4441fca0a27f5 ("lib: test module for find_*_bit() functions")
Signed-off-by: Yury Norov <ynorov@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Reported-by: Fengguang Wu <fengguang.wu@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/find_bit_benchmark.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff -puN lib/find_bit_benchmark.c~lib-avoid-soft-lockup-in-test_find_first_bit lib/find_bit_benchmark.c
--- a/lib/find_bit_benchmark.c~lib-avoid-soft-lockup-in-test_find_first_bit
+++ a/lib/find_bit_benchmark.c
@@ -132,7 +132,12 @@ static int __init find_bit_test(void)
test_find_next_bit(bitmap, BITMAP_LEN);
test_find_next_zero_bit(bitmap, BITMAP_LEN);
test_find_last_bit(bitmap, BITMAP_LEN);
- test_find_first_bit(bitmap, BITMAP_LEN);
+
+ /*
+ * test_find_first_bit() may take some time, so
+ * traverse only part of bitmap to avoid soft lockup.
+ */
+ test_find_first_bit(bitmap, BITMAP_LEN / 10);
test_find_next_and_bit(bitmap, bitmap2, BITMAP_LEN);
pr_err("\nStart testing find_bit() with sparse bitmap\n");
_
Patches currently in -mm which might be from ynorov@xxxxxxxxxxxxxxxxxx are
lib-avoid-soft-lockup-in-test_find_first_bit.patch
lib-micro-optimization-for-__bitmap_complement.patch
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