Re: [RFC PATCH v2] posix-timers: Support delivery of signals to the current thread

Oleg Nesterov
2023-01-25T12:44:05Z

On 01/12, Dmitry Vyukov wrote:
>
> --- a/kernel/time/posix-timers.c
> +++ b/kernel/time/posix-timers.c
> @@ -336,6 +336,7 @@ void posixtimer_rearm(struct kernel_siginfo *info)
> int posix_timer_event(struct k_itimer *timr, int si_private)
> {
> enum pid_type type;
> + struct pid *pid;
> int ret;
> /*
> * FIXME: if ->sigq is queued we can race with
> @@ -350,8 +351,9 @@ int posix_timer_event(struct k_itimer *timr, int si_private)
> */
> timr->sigq->info.si_sys_private = si_private;
>
> + pid = timr->it_pid ?: task_pid(current);
> type = !(timr->it_sigev_notify & SIGEV_THREAD_ID) ? PIDTYPE_TGID : PIDTYPE_PID;

can't resist... somehow the line above looks confusing to me, perhaps you
can change it to

type = (timr->it_sigev_notify & SIGEV_THREAD_ID) ? PIDTYPE_PID : PIDTYPE_TGID;

> -static struct pid *good_sigevent(sigevent_t * event)
> +static struct pid *good_sigevent(sigevent_t *event, clockid_t which_clock)
> {
> struct pid *pid = task_tgid(current);
> struct task_struct *rtn;
>
> switch (event->sigev_notify) {
> case SIGEV_SIGNAL | SIGEV_THREAD_ID:
> + /* This will use the current task for signals. */
> + if (which_clock == CLOCK_PROCESS_CPUTIME_ID &&
> + !event->sigev_notify_thread_id)
> + return NULL;

this doesn't look right, this skips the "sigev_signo" check below.

Other than that I see nothing wrong in this patch, but I forgot everything
about posix timers many years ago ;)

> @@ -527,9 +534,11 @@ static int do_timer_create(clockid_t which_clock, struct sigevent *event,
>
> if (event) {
> rcu_read_lock();
> - new_timer->it_pid = get_pid(good_sigevent(event));
> + pid = good_sigevent(event, which_clock);
> + if (!IS_ERR(pid))
> + new_timer->it_pid = get_pid(pid);

Another cosmetic nit, feel free to ignore... If you change good_sigevent()

case SIGEV_NONE:
- return pid;
+ return get_pid(pid);

you can remove this "if (!IS_ERR(pid))" code above.

Oleg.