On Wed, Feb 1, 2023 at 8:56 PM Eric Biggers <ebiggers@xxxxxxxxxx> wrote: > > On Wed, Feb 01, 2023 at 07:00:23PM -0800, Munehisa Kamata wrote: > > diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c > > index 8ac8b81bfee6..6e66c15f6450 100644 > > --- a/kernel/sched/psi.c > > +++ b/kernel/sched/psi.c > > @@ -1343,10 +1343,11 @@ void psi_trigger_destroy(struct psi_trigger *t) > > > > group = t->group; > > /* > > - * Wakeup waiters to stop polling. Can happen if cgroup is deleted > > - * from under a polling process. > > + * Wakeup waiters to stop polling and clear the queue to prevent it from > > + * being accessed later. Can happen if cgroup is deleted from under a > > + * polling process otherwise. > > */ > > - wake_up_interruptible(&t->event_wait); > > + wake_up_pollfree(&t->event_wait); > > > > mutex_lock(&group->trigger_lock); > > wake_up_pollfree() should only be used in extremely rare cases. Why can't the > lifetime of the waitqueue be fixed instead? waitqueue lifetime in this case is linked to cgroup_file_release(), which seems appropriate to me here. Unfortunately cgroup_file_release() is not directly linked to the file's lifetime. For more details see: https://lore.kernel.org/all/CAJuCfpFZ3B4530TgsSHqp5F_gwfrDujwRYewKReJru==MdEHQg@xxxxxxxxxxxxxx/#t . So, if we want to fix the lifetime of the waitqueue, we would have to tie cgroup_file_release() to the fput() somehow. IOW, the fix would have to be done at the cgroups or higher (kernfs?) layer. Thanks, Suren. > > - Eric
