[LTP] [PATCH 0/2] Fix sporadic failures in pids shell tests

[LTP] [PATCH 0/2] Fix sporadic failures in pids shell tests

[Andrea Cervesato]

Signed-off-by: Andrea Cervesato <andrea.cervesato@suse.com>
---
Andrea Cervesato (2):
      pids: fix cleanup of orphaned pids_task1 children
      tst_cgroup: tolerate ESRCH in cgroup_drain()

 lib/tst_cgroup.c                          | 2 +-
 testcases/kernel/controllers/pids/pids.sh | 5 +++--
 2 files changed, 4 insertions(+), 3 deletions(-)
---
base-commit: b4d31ea5d5c16628b9c45932fc98b929ca2ceece
change-id: 20260615-fix_pids_errors-19399419c8ee

Best regards,
-- 
Andrea Cervesato <andrea.cervesato@suse.com>


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[LTP] [PATCH 1/2] pids: fix cleanup of orphaned pids_task1 children

[Andrea Cervesato]

From: Andrea Cervesato <andrea.cervesato@suse.com>

pids_task1 forks a child that calls pause(), then the parent exits.
The orphaned child remains in the cgroup but gets reparented to init,
so it is not a child of the test shell.

stop_pids_tasks_path() reads cgroup.procs which includes this orphan.
kill -9 succeeds but wait fails with 'not a child of this shell'.
Using ROD for kill also unnecessarily aborts if the process is already
dead.

Fix by suppressing errors from both kill and wait, and add killall
for pids_task1 in cleanup() to catch any remaining orphans.

Signed-off-by: Andrea Cervesato <andrea.cervesato@suse.com>
---
 testcases/kernel/controllers/pids/pids.sh | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/testcases/kernel/controllers/pids/pids.sh b/testcases/kernel/controllers/pids/pids.sh
index 26a0c6a221ea63e683016ebfea33f2744800aaea..dd27b5616f0c4b55c625ca57efa2507325949b07 100755
--- a/testcases/kernel/controllers/pids/pids.sh
+++ b/testcases/kernel/controllers/pids/pids.sh
@@ -35,6 +35,7 @@ EOF
 cleanup()
 {
 	killall -9 pids_task2 >/dev/null 2>&1
+	killall -9 pids_task1 >/dev/null 2>&1
 
 	cgroup_cleanup
 }
@@ -79,8 +80,8 @@ stop_pids_tasks_path()
 	path=$1
 
 	for i in $(cat "$path/$task_list"); do
-		ROD kill -9 $i
-		wait $i
+		kill -9 $i 2>/dev/null
+		wait $i 2>/dev/null
 	done
 }
 

-- 
2.51.0


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Re: [LTP] pids: fix cleanup of orphaned pids_task1 children

[linuxtestproject.agent]

Hi Andrea,

On Mon, 15 Jun 2026, Andrea Cervesato wrote:
> pids: fix cleanup of orphaned pids_task1 children

Verdict - Reviewed

---
Note:

The agent can sometimes produce false positives although often its
findings are genuine. If you find issues with the review, please
comment this email or ignore the suggestions.

Regards,
LTP AI Reviewer

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Re: [LTP] [PATCH 1/2] pids: fix cleanup of orphaned pids_task1 children

[Li Wang]

> From: Andrea Cervesato <andrea.cervesato@suse.com>
> 
> pids_task1 forks a child that calls pause(), then the parent exits.
> The orphaned child remains in the cgroup but gets reparented to init,
> so it is not a child of the test shell.
> 
> stop_pids_tasks_path() reads cgroup.procs which includes this orphan.
> kill -9 succeeds but wait fails with 'not a child of this shell'.
> Using ROD for kill also unnecessarily aborts if the process is already
> dead.
> 
> Fix by suppressing errors from both kill and wait, and add killall
> for pids_task1 in cleanup() to catch any remaining orphans.
> 
> Signed-off-by: Andrea Cervesato <andrea.cervesato@suse.com>

Reviewed-by: Li Wang <li.wang@linux.dev>

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Regards,
Li Wang

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[LTP] [PATCH 2/2] tst_cgroup: tolerate ESRCH in cgroup_drain()

[Andrea Cervesato]

From: Andrea Cervesato <andrea.cervesato@suse.com>

A process can die between reading cgroup.procs and writing its PID
to the destination cgroup. When this happens, the kernel returns
ESRCH which is a normal race condition, not a test infrastructure
failure.

Skip ESRCH errors instead of aborting with TBROK.

Signed-off-by: Andrea Cervesato <andrea.cervesato@suse.com>
---
 lib/tst_cgroup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/tst_cgroup.c b/lib/tst_cgroup.c
index a37bf1516aabfbcb9a02fedd6fddb98e85ecc653..42d07912aebc0fae423b52f22c36c6beab0ee5c6 100644
--- a/lib/tst_cgroup.c
+++ b/lib/tst_cgroup.c
@@ -974,7 +974,7 @@ static void cgroup_drain(const enum tst_cg_ver ver,
 	for (tok = strtok(pid_list, "\n"); tok; tok = strtok(NULL, "\n")) {
 		ret = dprintf(fd, "%s", tok);
 
-		if (ret < (ssize_t)strlen(tok))
+		if (ret < (ssize_t)strlen(tok) && errno != ESRCH)
 			tst_brk(TBROK | TERRNO, "Failed to drain %s", tok);
 	}
 	SAFE_CLOSE(fd);

-- 
2.51.0


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Re: [LTP] [PATCH 2/2] tst_cgroup: tolerate ESRCH in cgroup_drain()

[Li Wang]

> From: Andrea Cervesato <andrea.cervesato@suse.com>
> 
> A process can die between reading cgroup.procs and writing its PID
> to the destination cgroup. When this happens, the kernel returns
> ESRCH which is a normal race condition, not a test infrastructure
> failure.
> 
> Skip ESRCH errors instead of aborting with TBROK.
> 
> Signed-off-by: Andrea Cervesato <andrea.cervesato@suse.com>
> ---
>  lib/tst_cgroup.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/tst_cgroup.c b/lib/tst_cgroup.c
> index a37bf1516aabfbcb9a02fedd6fddb98e85ecc653..42d07912aebc0fae423b52f22c36c6beab0ee5c6 100644
> --- a/lib/tst_cgroup.c
> +++ b/lib/tst_cgroup.c
> @@ -974,7 +974,7 @@ static void cgroup_drain(const enum tst_cg_ver ver,
>  	for (tok = strtok(pid_list, "\n"); tok; tok = strtok(NULL, "\n")) {
>  		ret = dprintf(fd, "%s", tok);
>  
> -		if (ret < (ssize_t)strlen(tok))
> +		if (ret < (ssize_t)strlen(tok) && errno != ESRCH)

errno is only meaningful after a call that actually failed (ret < 0).
With a short but non-negative return, errno holds whatever value some
earlier libc/syscall left there.

So maybe better like this:

    if (ret < (ssize_t)strlen(tok)) {
        if (ret < 0 && errno == ESRCH)
            continue;

        tst_brk(TBROK | TERRNO, "Failed to drain %s", tok);
    }

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Regards,
Li Wang

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