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cgroup/pids: Restore pids.events notifications in local mode

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A fork rejected by the pids controller increments the counter reported by
pids.events. When local event accounting is selected, however, pids_event()
returns after notifying only events_local_file, leaving pids.events pollers
asleep.

On legacy hierarchies, pids.events.local does not exist. With
pids_localevents, pids.events reports the same local counter. In both
cases, pids.events changes without generating a notification.

This can be reproduced with a pids_localevents mount:

    mkdir /tmp/test
    mount -t cgroup2 -o pids_localevents none /tmp/test
    mkdir /tmp/test/t
    echo 1 > /tmp/test/t/pids.max
    cat /tmp/test/t/pids.events                 # max 0
    timeout 3 inotifywait -e modify /tmp/test/t/pids.events &
    sh -c 'echo $$ > /tmp/test/t/cgroup.procs; (true &)' 2>/dev/null
    wait
    cat /tmp/test/t/pids.events                 # max 1

Without this patch, inotifywait times out without reporting an event.
Notify pids.events before returning from the local event path.

Fixes: 3f26a885a0 ("cgroup/pids: Add pids.events.local")
Cc: stable@vger.kernel.org # v6.11+
Signed-off-by: Guopeng Zhang <zhangguopeng@kylinos.cn>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Guopeng Zhang 2026-09-24 17:15:36 +08:00 committed by Tejun Heo
parent c774ec8f0a
commit 1765a153d9
1 changed files with 5 additions and 0 deletions
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5
kernel/cgroup/pids.c
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@ -253,6 +253,11 @@ static void pids_event(struct pids_cgroup *pids_forking,
}
if (!cgroup_subsys_on_dfl(pids_cgrp_subsys) ||
cgrp_dfl_root.flags & CGRP_ROOT_PIDS_LOCAL_EVENTS) {
/*
* pids.events reports the local counter on legacy hierarchies
* and when pids_localevents is enabled.
*/
cgroup_file_notify(&p->events_file);
cgroup_file_notify(&p->events_local_file);
return;
}