linux-kernel - Re: [PATCH v2 5/7] selftests/mm: Fix child process exit codes in ksm_functional

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Message-ID: <9586f8ff-3b34-4613-853b-0c808fcbb9d2@redhat.com>
Date: Thu, 3 Jul 2025 10:33:13 +0200
From: David Hildenbrand <david@...hat.com>
To: Aboorva Devarajan <aboorvad@...ux.ibm.com>, akpm@...ux-foundation.org,
 Liam.Howlett@...cle.com, lorenzo.stoakes@...cle.com, shuah@...nel.org,
 pfalcato@...e.de, ziy@...dia.com, baolin.wang@...ux.alibaba.com,
 npache@...hat.com, ryan.roberts@....com, dev.jain@....com, baohua@...nel.org
Cc: linux-mm@...ck.org, linux-kselftest@...r.kernel.org,
 linux-kernel@...r.kernel.org, donettom@...ux.ibm.com, ritesh.list@...il.com
Subject: Re: [PATCH v2 5/7] selftests/mm: Fix child process exit codes in
 ksm_functional_tests

On 03.07.25 08:06, Aboorva Devarajan wrote:
> In ksm_functional_tests, test_child_ksm() returned negative values
> to indicate errors. However, when passed to exit(), these were
> interpreted as large unsigned values (e.g, -2 became 254), leading to
> incorrect handling in the parent process. As a result, some tests
> appeared to be skipped or silently failed.
> 
> This patch changes test_child_ksm() to return positive error codes
> (1, 2, 3) and updates test_child_ksm_err() to interpret them correctly.
> This ensures the parent accurately detects and reports child process
> failures.
> 
> --------------
> Before patch:
> --------------
> - [RUN] test_unmerge
> ok 1 Pages were unmerged
> ...
> - [RUN] test_prctl_fork
> - No pages got merged
> - [RUN] test_prctl_fork_exec
> ok 7 PR_SET_MEMORY_MERGE value is inherited
> ...
> Bail out! 1 out of 8 tests failed
> - Planned tests != run tests (9 != 8)
> - Totals: pass:7 fail:1 xfail:0 xpass:0 skip:0 error:0
> 
> --------------
> After patch:
> --------------
> - [RUN] test_unmerge
> ok 1 Pages were unmerged
> ...
> - [RUN] test_prctl_fork
> - No pages got merged
> not ok 7 Merge in child failed
> - [RUN] test_prctl_fork_exec
> ok 8 PR_SET_MEMORY_MERGE value is inherited
> ...
> Bail out! 2 out of 9 tests failed
> - Totals: pass:7 fail:2 xfail:0 xpass:0 skip:0 error:0
> 
> Fixes: 6c47de3be3a0 ("selftest/mm: ksm_functional_tests: extend test case for ksm fork/exec")
> Signed-off-by: Aboorva Devarajan <aboorvad@...ux.ibm.com>

BTW, when I run the test, I get this weird output

TAP version 13
1..9
# [RUN] test_unmerge
ok 1 Pages were unmerged
# [RUN] test_unmerge_zero_pages
ok 2 KSM zero pages were unmerged
# [RUN] test_unmerge_discarded
ok 3 Pages were unmerged
# [RUN] test_unmerge_uffd_wp
ok 4 Pages were unmerged
# [RUN] test_prot_none
ok 5 Pages were unmerged
# [RUN] test_prctl
ok 6 Setting/clearing PR_SET_MEMORY_MERGE works
# [RUN] test_prctl_fork
ok 7 PR_SET_MEMORY_MERGE value is inherited
# [RUN] test_prctl_fork_exec

^ where is the test?

# [RUN] test_prctl_unmerge
ok 8 Pages were unmerged
# Planned tests != run tests (9 != 8)
# Totals: pass:8 fail:0 xfail:0 xpass:0 skip:0 error:0

^ what?

ok 8 PR_SET_MEMORY_MERGE value is inherited
# [RUN] test_prctl_unmerge
ok 9 Pages were unmerged
# Totals: pass:9 fail:0 xfail:0 xpass:0 skip:0 error:0

^ huh, what now?

-- 
Cheers,

David / dhildenb