[LTP] [PATCH v2 0/2] Fix sporadic failures in pids shell tests

[LTP] [PATCH v2 0/2] Fix sporadic failures in pids shell tests

[Andrea Cervesato]

Signed-off-by: Andrea Cervesato <andrea.cervesato@suse.com>
---
Changes in v2:
- handle ESRCH only when ret < 0
- Link to v1: https://lore.kernel.org/r/20260615-fix_pids_errors-v1-0-99a54a205180@suse.com

---
Andrea Cervesato (2):
      pids: fix cleanup of orphaned pids_task1 children
      tst_cgroup: tolerate ESRCH in cgroup_drain()

 lib/tst_cgroup.c                          | 6 +++++-
 testcases/kernel/controllers/pids/pids.sh | 5 +++--
 2 files changed, 8 insertions(+), 3 deletions(-)
---
base-commit: b4d31ea5d5c16628b9c45932fc98b929ca2ceece
change-id: 20260615-fix_pids_errors-19399419c8ee

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


-- 
Mailing list info: https://lists.linux.it/listinfo/ltp

[LTP] [PATCH v2 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.

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


-- 
Mailing list info: https://lists.linux.it/listinfo/ltp

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

[linuxtestproject.agent]

Hi Andrea,

On Tue, 16 Jun 2026, Andrea Cervesato wrote:
> pids: fix cleanup of orphaned pids_task1 children
> tst_cgroup: tolerate ESRCH in cgroup_drain()

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

-- 
Mailing list info: https://lists.linux.it/listinfo/ltp

[LTP] [PATCH v2 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 | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/lib/tst_cgroup.c b/lib/tst_cgroup.c
index a37bf1516aabfbcb9a02fedd6fddb98e85ecc653..f548c0e01cf60803ad4c1e898e7ec2d39dc33c84 100644
--- a/lib/tst_cgroup.c
+++ b/lib/tst_cgroup.c
@@ -974,8 +974,12 @@ 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)) {
+			if (ret < 0 && errno == ESRCH)
+				continue;
+
 			tst_brk(TBROK | TERRNO, "Failed to drain %s", tok);
+		}
 	}
 	SAFE_CLOSE(fd);
 }

-- 
2.51.0


-- 
Mailing list info: https://lists.linux.it/listinfo/ltp

Re: [LTP] [PATCH v2 2/2] tst_cgroup: tolerate ESRCH in cgroup_drain()

[Li Wang]

On Tue, Jun 16, 2026 at 10:30:07AM +0200, Andrea Cervesato wrote:
> 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>

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

-- 
Regards,
Li Wang

-- 
Mailing list info: https://lists.linux.it/listinfo/ltp

Re: [LTP] [PATCH v2 2/2] tst_cgroup: tolerate ESRCH in cgroup_drain()

[Cyril Hrubis]

Hi!
> 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 | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/tst_cgroup.c b/lib/tst_cgroup.c
> index a37bf1516aabfbcb9a02fedd6fddb98e85ecc653..f548c0e01cf60803ad4c1e898e7ec2d39dc33c84 100644
> --- a/lib/tst_cgroup.c
> +++ b/lib/tst_cgroup.c
> @@ -974,8 +974,12 @@ 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)) {
> +			if (ret < 0 && errno == ESRCH)
> +				continue;

Maybe we can print tst_res(TINFO, "Pid %s died during drain", tok);
here as well, so that when this happens we will have the information in
the test log.

Otherwise:

Reviewed-by: Cyril Hrubis <chrubis@suse.cz>

>  			tst_brk(TBROK | TERRNO, "Failed to drain %s", tok);
> +		}
>  	}
>  	SAFE_CLOSE(fd);
>  }
> 
> -- 
> 2.51.0
> 
> 
> -- 
> Mailing list info: https://lists.linux.it/listinfo/ltp

-- 
Cyril Hrubis
chrubis@suse.cz

-- 
Mailing list info: https://lists.linux.it/listinfo/ltp

Re: [LTP] [PATCH v2 2/2] tst_cgroup: tolerate ESRCH in cgroup_drain()

[Andrea Cervesato via ltp]

> Maybe we can print tst_res(TINFO, "Pid %s died during drain", tok);
> here as well, so that when this happens we will have the information in
> the test log.

What about TDEBUG ?

--
Andrea Cervesato
SUSE QE Automation Engineer Linux
andrea.cervesato@suse.com

-- 
Mailing list info: https://lists.linux.it/listinfo/ltp

Re: [LTP] [PATCH v2 2/2] tst_cgroup: tolerate ESRCH in cgroup_drain()

[Cyril Hrubis]

Hi!
> > Maybe we can print tst_res(TINFO, "Pid %s died during drain", tok);
> > here as well, so that when this happens we will have the information in
> > the test log.
> 
> What about TDEBUG ?

I was thinking about TDEBUG but in the end I think TINFO is better
because:

- the message is not going to be printed very often
- it's visible by default, i.e. included in logs from CI

-- 
Cyril Hrubis
chrubis@suse.cz

-- 
Mailing list info: https://lists.linux.it/listinfo/ltp

Re: [LTP] [PATCH v2 2/2] tst_cgroup: tolerate ESRCH in cgroup_drain()

[Andrea Cervesato via ltp]

Merged, Thanks!

With suggested @Cyril TINFO message on ESRCH.

--
Andrea Cervesato
SUSE QE Automation Engineer Linux
andrea.cervesato@suse.com

-- 
Mailing list info: https://lists.linux.it/listinfo/ltp