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selftests/bpf: fix flaky build_id test

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The build_id selftest occasionally fails because MADV_PAGEOUT
does not guarantee the immediate eviction of the page. The test
assumes eviction happens and proceeds without verifying
that the page was actually reclaimed, leading to false test
failures.

Fix the test by retrying the page-out sequence until eviction
is successful, instead of relying on a single MADV_PAGEOUT attempt.

Signed-off-by: Gregory Bell <grbell@redhat.com>
Link: https://lore.kernel.org/r/038bd27c69dd3a16958894fcb19e4fb6fbfe317e.1771338492.git.grbell@redhat.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Gregory Bell
2026-02-17 09:32:36 -05:00
committed by Alexei Starovoitov
parent b0a67f310b
commit d820fa3114
1 changed files with 16 additions and 3 deletions
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19
tools/testing/selftests/bpf/uprobe_multi.c
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@@ -100,6 +100,9 @@ int __attribute__((weak)) trigger_uprobe(bool build_id_resident)
int page_sz = sysconf(_SC_PAGESIZE);
void *addr;
unsigned char vec[1];
int poll = 0;
/* page-align build ID start */
addr = (void *)((uintptr_t)&build_id_start & ~(page_sz - 1));
@@ -108,9 +111,19 @@ int __attribute__((weak)) trigger_uprobe(bool build_id_resident)
* do MADV_POPULATE_READ, and then MADV_PAGEOUT, if necessary
*/
madvise(addr, page_sz, MADV_POPULATE_READ);
if (!build_id_resident)
madvise(addr, page_sz, MADV_PAGEOUT);
if (!build_id_resident) {
do {
madvise(addr, page_sz, MADV_PAGEOUT);
/* check if page has been evicted */
mincore(addr, page_sz, vec);
if (!(vec[0] & 1))
break;
/* if page is still resident re-attempt MADV_POPULATE_READ/MADV_PAGEOUT */
madvise(addr, page_sz, MADV_POPULATE_READ);
poll++;
usleep(100);
} while (poll < 500);
}
(void)uprobe();
return 0;