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| author | Michal Koutný <mkoutny@suse.com> | 2023-10-09 15:58:11 +0200 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2023-10-09 06:42:05 -1000 |
| commit | 1ca0b605150501b7dc59f3016271da4eb3e96fce (patch) | |
| tree | 7ad8733ea44511c6e188f27d622936224c1c3477 /kernel/cgroup | |
| parent | 94f6f0550c625fab1f373bb86a6669b45e9748b3 (diff) | |
| download | lwn-1ca0b605150501b7dc59f3016271da4eb3e96fce.tar.gz lwn-1ca0b605150501b7dc59f3016271da4eb3e96fce.zip | |
cgroup: Remove duplicates in cgroup v1 tasks file
One PID may appear multiple times in a preloaded pidlist.
(Possibly due to PID recycling but we have reports of the same
task_struct appearing with different PIDs, thus possibly involving
transfer of PID via de_thread().)
Because v1 seq_file iterator uses PIDs as position, it leads to
a message:
> seq_file: buggy .next function kernfs_seq_next did not update position index
Conservative and quick fix consists of removing duplicates from `tasks`
file (as opposed to removing pidlists altogether). It doesn't affect
correctness (it's sufficient to show a PID once), performance impact
would be hidden by unconditional sorting of the pidlist already in place
(asymptotically).
Link: https://lore.kernel.org/r/20230823174804.23632-1-mkoutny@suse.com/
Suggested-by: Firo Yang <firo.yang@suse.com>
Signed-off-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: stable@vger.kernel.org
Diffstat (limited to 'kernel/cgroup')
| -rw-r--r-- | kernel/cgroup/cgroup-v1.c | 5 |
1 files changed, 2 insertions, 3 deletions
diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c index c487ffef6652..76db6c67e39a 100644 --- a/kernel/cgroup/cgroup-v1.c +++ b/kernel/cgroup/cgroup-v1.c @@ -360,10 +360,9 @@ static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type, } css_task_iter_end(&it); length = n; - /* now sort & (if procs) strip out duplicates */ + /* now sort & strip out duplicates (tgids or recycled thread PIDs) */ sort(array, length, sizeof(pid_t), cmppid, NULL); - if (type == CGROUP_FILE_PROCS) - length = pidlist_uniq(array, length); + length = pidlist_uniq(array, length); l = cgroup_pidlist_find_create(cgrp, type); if (!l) { |