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

Oleg Nesterov
2023-01-25T15:18:15Z

On 01/25, Oleg Nesterov wrote:
>
> Other than that I see nothing wrong in this patch, but I forgot everything
> about posix timers many years ago ;)

Stupid question. Am I right that in posix_timer_event()

same_thread_group(current, pid_task(timr->it_pid, PIDTYPE_PID))

is always true?

If yes, perhaps we can do a much simpler change which doesn't even affect API?
See the trivial patch below.

send_sigqueue(PIDTYPE_TGID) notify any thread in thread group, so this doesn't
really change the semantics, just complete_signal() will likely choose "current"
as a target for signal_wake_up() and iiuc this is what we want for balancing?

Oleg.

diff --git a/kernel/time/posix-timers.c b/kernel/time/posix-timers.c
index 5dead89308b7..e38b53a0f814 100644
--- 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;

- type = !(timr->it_sigev_notify & SIGEV_THREAD_ID) ? PIDTYPE_TGID : PIDTYPE_PID;
- ret = send_sigqueue(timr->sigq, timr->it_pid, type);
+ type = (timr->it_sigev_notify & SIGEV_THREAD_ID) ? PIDTYPE_PID : PIDTYPE_TGID;
+ pid = (type == PIDTYPE_PID) ? timr->it_pid : task_pid(current);
+ ret = send_sigqueue(timr->sigq, pid, type);
/* If we failed to send the signal the timer stops. */
return ret > 0;
}