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Message-ID: <1b6e8526-59cb-4de0-bd82-8b0964cb6233@linux.ibm.com>
Date: Thu, 3 Jul 2025 20:01:45 +0530
From: Donet Tom <donettom@...ux.ibm.com>
To: David Hildenbrand <david@...hat.com>,
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, ritesh.list@...il.com
Subject: Re: [PATCH v2 5/7] selftests/mm: Fix child process exit codes in
ksm_functional_tests
On 7/3/25 2:44 PM, David Hildenbrand wrote:
> On 03.07.25 10:51, Donet Tom wrote:
>> Hi David
>>
>> On 7/3/25 2:03 PM, David Hildenbrand wrote:
>>> 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?
>>>
>>
>> The problem with the exec test is that it uses its own binary to exec.
>>
>> } else if (child_pid == 0) {
>> char *prg_name = "./ksm_functional_tests";
>> char *argv_for_program[] = { prg_name,
>> FORK_EXEC_CHILD_PRG_NAME, NULL };
>>
>> execv(prg_name, argv_for_program);
>> return;
>> }
> > > So we should run it on the same directory where the binary present.
>
> So, I assume the execv fails. We should handle that, and figure out
> why it fails.
>
> diff --git a/tools/testing/selftests/mm/ksm_functional_tests.c
> b/tools/testing/selftests/mm/ksm_functional_tests.c
> index d8bd1911dfc0a..0ddbb390df33b 100644
> --- a/tools/testing/selftests/mm/ksm_functional_tests.c
> +++ b/tools/testing/selftests/mm/ksm_functional_tests.c
> @@ -527,6 +527,8 @@ static void test_child_ksm_err(int status)
> ksft_test_result_fail("Merge in child failed\n");
> else if (status == -3)
> ksft_test_result_skip("Merge in child skipped\n");
> + else if (status == 4)
> + ksft_test_result_fail("Binary not found\n");
> }
>
> /* Verify that prctl ksm flag is inherited. */
> @@ -598,7 +600,7 @@ static void test_prctl_fork_exec(void)
> char *argv_for_program[] = { prg_name,
> FORK_EXEC_CHILD_PRG_NAME };
>
> execv(prg_name, argv_for_program);
> - return;
> + exit(4);
> }
>
> if (waitpid(child_pid, &status, 0) > 0) {
>
> results in
>
> 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
> not ok 8 Binary not found
> # [RUN] test_prctl_unmerge
> ok 9 Pages were unmerged
> Bail out! 1 out of 9 tests failed
> # Totals: pass:8 fail:1 xfail:0 xpass:0 skip:0 error:0
Thanks David.
We will add this in next version.
>
>
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