[Devel] [PATCH VZ10] fs/fuse kio: avoid hung-task warning on krpc_watcher

[Alexey Kuznetsov]

Nack!

This is not a correct solution. The task is still accounted as
contributor to load avarage
which is inacceptable.

Look how other kthreads do it. Ancient mechanism used
TASK_INTERUPTIBLE and blocked signals or cleared them.
Also we had to handle freeze. Generally it was chumbersome. What's
about modern state: I still did not figure this out.



On Fri, Jun 5, 2026 at 5:26 PM Liu Kui <kui.liu at virtuozzo.com> wrote:
>
> The indefinite wait_event() makes the watcher in TASK_UNINTERRUPTIBLE,
> so a long-lived watched process triggers khungtaskd:
>
>   INFO: task krpc_watcher:225326 blocked for more than 1228 seconds.
>
> Use wait_event_timeout() with a 60s period in a while-loop so the
> task periodically reschedules and the warning goes away.
>
> Signed-off-by: Liu Kui <kui.liu at virtuozzo.com>
> ---
>  fs/fuse/kio/pcs/pcs_krpc.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/fs/fuse/kio/pcs/pcs_krpc.c b/fs/fuse/kio/pcs/pcs_krpc.c
> index 7d5a9619276d..03ae995eaf55 100644
> --- a/fs/fuse/kio/pcs/pcs_krpc.c
> +++ b/fs/fuse/kio/pcs/pcs_krpc.c
> @@ -665,12 +665,22 @@ static bool process_has_exited(struct pid *pid)
>         return exited;
>  }
>
> +static inline bool krpc_watcher_should_stop(struct pid *watched_pid)
> +{
> +       return process_has_exited(watched_pid) || kthread_should_stop();
> +}
> +
>  static int krpc_watcher_fn(void *data)
>  {
>         struct pcs_krpc_set *krpcs = data;
> +       struct pid *watched_pid = krpcs->watched_pid;
>
> -       wait_event(krpcs->watched_pid->wait_pidfd,
> -                       process_has_exited(krpcs->watched_pid) || kthread_should_stop());
> +       while (!krpc_watcher_should_stop(watched_pid)) {
> +               /* Periodic wakeup so khungtaskd doesn't flag the watcher. */
> +               wait_event_timeout(watched_pid->wait_pidfd,
> +                                       krpc_watcher_should_stop(watched_pid),
> +                                       60 * HZ);
> +       }
>
>         kthread_stop(krpcs->sender_task);
>         put_task_struct(krpcs->sender_task);
> --
> 2.50.1 (Apple Git-155)