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# thrd_yield

From cppreference.com
< c‎ | thread

Defined in header `<threads.h>` |  |
void thrd_yield(); |  | (since C11)

Provides a hint to the implementation to reschedule the execution of threads, allowing other threads to run.

### [edit] Parameters

(none)

### [edit] Return value

(none)

### [edit] Notes

The exact behavior of this function depends on the implementation, in particular on the mechanics of the OS scheduler in use and the state of the system. For example, a first-in-first-out realtime scheduler (`SCHED_FIFO` in Linux) would suspend the current thread and put it on the back of the queue of the same-priority threads that are ready to run (and if there are no other threads at the same priority, `yield` has no effect).

The POSIX equivalent of this function is sched_yield.

### [edit] Example

Run this code

    #include <stdio.h>
    #include <time.h>
    #include <threads.h>

    // utility function: difference between timespecs in microseconds
    double usdiff(struct timespec s, struct timespec e)
    {
        double sdiff = difftime(e.tv_sec, s.tv_sec);
        long nsdiff = e.tv_nsec - s.tv_nsec;
        if(nsdiff < 0) return 1000000*(sdiff-1) + (1000000000L+nsdiff)/1000.0;
        else return 1000000*(sdiff) + nsdiff/1000.0;
    }

    // busy wait while yielding
    void sleep_100us()
    {
        struct timespec start, end;
        timespec_get(&start, TIME_UTC);
        do {
            thr_yield();
            timespec_get(&end, TIME_UTC);
        } while(usdiff(start, end) < 100.0);
    }

    int main()
    {
        struct timespec start, end;
        timespec_get(&start, TIME_UTC);
        sleep_100us();
        timespec_get(&end, TIME_UTC);
        printf("Waited for %.3f us\n", usdiff(start, end));
    }

Possible output:

    Waited for 100.344 us

### [edit] References

- C11 standard (ISO/IEC 9899:2011):

  - 7.26.5.8 The thrd_yield function (p: 385)

### [edit] See also

thrd_sleep (C11) | suspends execution of the calling thread for the given period of time (function) [edit]

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