atmega: thread exit deadlock

[Josar]

When a thread ends and was not set to sleep there is a deadlock, might be related to #6526.
Enabling debug in scheduler.c removes the deadlock but then all xtimer values are wrong.

Testing with this

#include <inttypes.h>
#include <stdio.h>

#include "xtimer.h"
#include "timex.h"
#include "thread.h"

#include "Board.h"

volatile uint32_t end_times[2];

static char stack[THREAD_STACKSIZE_MAIN];
static void *_thread(void *arg)
{
    (void) arg;

    puts("thread(): waiting going to sleep!");

    //while (1) {
        thread_sleep();
        end_times[1] = _xtimer_now();
        printf("Woke up.\n");
        /* deadlock if thread is not put to sleep before return */
        /* But if ENABLE_DEBUG is activated in sched.c no deadlock,
         *  but then the timer values are wrong */
        //thread_sleep();
    //}
    return NULL;
}

int main(void)
{
    xtimer_t xtimer[2];
    uint32_t start[2];
    uint32_t interval[2];

    kernel_pid_t pid_main = thread_getpid();

    kernel_pid_t pid_1 = thread_create(stack,
                                       sizeof(stack),
                                       THREAD_PRIORITY_MAIN - 1,
                                       THREAD_CREATE_STACKTEST,
                                       _thread,
                                       NULL,
                                       "second_thread");

    interval[1] = _xtimer_usec_from_ticks(40000);
    start[1] = _xtimer_now();
    xtimer_set_wakeup(&xtimer[1], interval[1], pid_1);

    interval[0] = _xtimer_usec_from_ticks(50000);
    start[0] = _xtimer_now();
    xtimer_set_wakeup(&xtimer[0], interval[0], pid_main);

    thread_sleep();
    end_times[0] = _xtimer_now();
    for (unsigned n = 0; n < 2; n++) {
        uint32_t diff = end_times[n] - start[n];
        printf("%" PRIu32 " %" PRIu32 " slept for %" PRIu32 " ticks (%" PRIu32
               " us) expected %" PRIu32 " ticks, diff %" PRIu32 " ticks\n",
               start[n], end_times[n], diff, _xtimer_usec_from_ticks(diff),
               _xtimer_ticks_from_usec(interval[n]), diff - _xtimer_ticks_from_usec(interval[n])
               );
    }

    for (unsigned n = 0; n < 5; n++) {
        uint32_t start, end, diff, interval= 10000;

        start = _xtimer_now();
        _xtimer_tsleep32(interval);
        end = _xtimer_now();

        diff = end - start;

        printf("%" PRIu32 " %" PRIu32 " slept for %" PRIu32 " ticks (%" PRIu32
               " us) expected %" PRIu32 " ticks, diff %" PRIu32 " ticks\n",
               start, end, diff, _xtimer_usec_from_ticks(diff),
               interval, diff - interval );
    }

    return 0;
}

[ZetaR60]

@Josar does this issue still exist since #8904 has been merged?

[Josar]

@ZetaR60 deadlock seems to be resolved.