diff options
| author | Tejun Heo <tj@kernel.org> | 2026-03-24 10:21:25 -1000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2026-04-11 14:29:23 +0200 |
| commit | 78c72bce4a87819126211c0d24e18350010604fb (patch) | |
| tree | e858af1d5081a04620d332cc8105c69efadb9d99 /include | |
| parent | c7de0861526b8b62b1c4978b55ec792ffc941114 (diff) | |
cgroup: Wait for dying tasks to leave on rmdir
[ Upstream commit 1b164b876c36c3eb5561dd9b37702b04401b0166 ]
a72f73c4dd9b ("cgroup: Don't expose dead tasks in cgroup") hid PF_EXITING
tasks from cgroup.procs so that systemd doesn't see tasks that have already
been reaped via waitpid(). However, the populated counter (nr_populated_csets)
is only decremented when the task later passes through cgroup_task_dead() in
finish_task_switch(). This means cgroup.procs can appear empty while the
cgroup is still populated, causing rmdir to fail with -EBUSY.
Fix this by making cgroup_rmdir() wait for dying tasks to fully leave. If the
cgroup is populated but all remaining tasks have PF_EXITING set (the task
iterator returns none due to the existing filter), wait for a kick from
cgroup_task_dead() and retry. The wait is brief as tasks are removed from the
cgroup's css_set between PF_EXITING assertion in do_exit() and
cgroup_task_dead() in finish_task_switch().
v2: cgroup_is_populated() true to false transition happens under css_set_lock
not cgroup_mutex, so retest under css_set_lock before sleeping to avoid
missed wakeups (Sebastian).
Fixes: a72f73c4dd9b ("cgroup: Don't expose dead tasks in cgroup")
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202603222104.2c81684e-lkp@intel.com
Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Bert Karwatzki <spasswolf@web.de>
Cc: Michal Koutny <mkoutny@suse.com>
Cc: cgroups@vger.kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/cgroup-defs.h | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h index f7cc60de0058..2bff3e2be0d3 100644 --- a/include/linux/cgroup-defs.h +++ b/include/linux/cgroup-defs.h @@ -609,6 +609,9 @@ struct cgroup { /* used to wait for offlining of csses */ wait_queue_head_t offline_waitq; + /* used by cgroup_rmdir() to wait for dying tasks to leave */ + wait_queue_head_t dying_populated_waitq; + /* used to schedule release agent */ struct work_struct release_agent_work; |