[Bug time/28739] New: Timer doesn't send SIGSTOP signal after expiration

["mmedon at student dot agh.edu.pl" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=28739

            Bug ID: 28739
           Summary: Timer doesn't send SIGSTOP signal after expiration
           Product: glibc
           Version: 2.34
            Status: UNCONFIRMED
          Severity: critical
          Priority: P2
         Component: time
          Assignee: unassigned at sourceware dot org
          Reporter: mmedon at student dot agh.edu.pl
  Target Milestone: ---

Timer doesn't send signal (SIGSTOP/SIGTSTP/SIGTTIN/SIGTTOU) when the time
period between timer expiration and SIGCONT delivering is at least two times
longer than value in itimerspec.

Code example:

#include <stdio.h>
#include <signal.h>
#include <time.h>
#include <stdlib.h>
#include <unistd.h>

int main(int argc, char *argv[]) {


    printf("PID: %d \n", getpid());
    timer_t timer;
    struct sigevent sev;
    sev.sigev_notify = SIGEV_SIGNAL;
    sev.sigev_signo = SIGSTOP;

    struct timespec timeForTimer = {.tv_sec = 10, .tv_nsec = 0};
    struct itimerspec ts = {.it_interval = timeForTimer, .it_value =
timeForTimer};

    if (timer_create(CLOCK_REALTIME, &sev, &timer) == -1) {
        perror("Error in timer_create!\n");
        exit(EXIT_FAILURE);
    }
    if (timer_settime(timer, 0, &ts, NULL) == -1) {
        perror("Error in timer_settime!\n");
        exit(EXIT_FAILURE);
    }

    struct timespec timeToWaitInLoop = {.tv_sec = 5, .tv_nsec = 0};

    for (;;) {
        time_t t = time(NULL);
        struct tm tm = *localtime(&t);
        printf("Time: %02d:%02d:%02d\n", tm.tm_hour, tm.tm_min, tm.tm_sec);
        nanosleep(&timeToWaitInLoop, NULL);
    }


}


Example output:
PID: 19139 
Time: 17:16:54
Time: 17:16:59 <- then SIGSTOP came
Time: 17:17:30 <- then I sent SIGCONT (from bash)
Time: 17:17:35
Time: 17:17:40
Time: 17:17:45
Time: 17:17:50

We should expect next SIGSTOP signal but it never comes
I also have created a thread on unix.stackexchange 
https://unix.stackexchange.com/questions/684192/specific-behavior-of-timers-with-sigev-notify-sigstop-signal

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