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selftests/bpf: End the loop of parallel_test_bitmap after 50 ms

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The two progs of parallel_test_bitmap change bits of the same words in a
loop of 10000000 iterations with can_loop. The loop goes on until may_goto
stops it. The functions that it calls retry a cmpxchg that fails:

  do {
          ...
          actual = cmpxchg(&bmp->bits[idx], old, new);
          if (actual == old)
                  return true;
  } while (can_loop);
  return false;

The retry is always possible only while each stack frame has a time slice
of its own. With one time slice for all may_goto of a prog, a function that
is called after the time is up makes no iteration. The bit does not change,
and the test fails with -EINVAL, in 53 of 900 runs.

Leave the loop after 50 ms.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://patch.msgid.link/20261031215543.682284-5-alexei.starovoitov@gmail.com
This commit is contained in:
Alexei Starovoitov 2026-10-31 21:55:38 +00:00
parent 40a3a2e686
commit 5eced83779
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1 changed files with 10 additions and 0 deletions
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10
tools/testing/selftests/bpf/libarena/selftests/test_parallel_bitmap.bpf.c
View File

@ -11,6 +11,7 @@
#define TEST_BITMAP_BITS (2 * BITS_PER_LONG_LONG)
#define TEST_BITMAP_SYNC_SPINS BPF_MAX_LOOPS
#define TEST_BITMAP_ITERS 10 * 1000 * 1000
#define TEST_BITMAP_NSEC (50 * 1000 * 1000)
static struct arena_bitmap __arena *bitmap;
static volatile u64 started;
@ -129,6 +130,7 @@ static int bitmap_test_common_single(int parity)
static int bitmap_test_common(int parity)
{
u64 start;
int ret;
u32 i;
@ -138,6 +140,7 @@ static int bitmap_test_common(int parity)
if (ret)
return ret;
start = bpf_ktime_get_ns();
for (i = zero; i < TEST_BITMAP_ITERS && can_loop; i++) {
ret = bitmap_test_common_single(parity);
if (ret)
@ -147,6 +150,13 @@ static int bitmap_test_common(int parity)
break;
bitmap_test_reset_single(parity);
/*
* Stop before the time slice of may_goto is used up. After that the
* bmp_*() functions can't retry a cmpxchg that fails.
*/
if (bpf_ktime_get_ns() - start > TEST_BITMAP_NSEC)
break;
}
return 0;