On Tue, Jul 23, 2019 at 02:45:39PM +0800, Jason Xing wrote:
> Only when calling the poll syscall the first time can user
> receive POLLPRI correctly. After that, user always fails to
> acquire the event signal.
>
> Reproduce case:
> 1. Get the monitor code in Documentation/accounting/psi.txt
> 2. Run it, and wait for the event triggered.
> 3. Kill and restart the process.
>
> If the user doesn't kill the monitor process, it seems the
> poll_work works fine. After killing and restarting the monitor,
> the poll_work in kernel will never run again due to the wrong
> value of poll_scheduled. Therefore, we should reset the value
> as group_init() does after the last trigger is destroyed.
>
> Signed-off-by: Jason Xing <kerneljasonx...@linux.alibaba.com>
Reviewed-by: Caspar Zhang <cas...@linux.alibaba.com>
> ---
> kernel/sched/psi.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
> index 7acc632..66f4385 100644
> --- a/kernel/sched/psi.c
> +++ b/kernel/sched/psi.c
> @@ -1133,6 +1133,12 @@ static void psi_trigger_destroy(struct kref *ref)
> if (kworker_to_destroy) {
> kthread_cancel_delayed_work_sync(&group->poll_work);
> kthread_destroy_worker(kworker_to_destroy);
> + /*
> + * The poll_work should have the chance to be put into the
> + * kthread queue when calling poll syscall next time. So
> + * reset poll_scheduled to zero as group_init() does
> + */
> + atomic_set(&group->poll_scheduled, 0);
> }
> kfree(t);
> }
> --
> 1.8.3.1
>
--
Thanks,
Caspar
