thrd_yield

 

C

Language

Headers

Type support

Program utilities

Variadic function support

Error handling

Dynamic memory management

Date and time utilities

Strings library

Algorithms

Numerics

Input/output support

Localization support

Atomic operations (C11)

Thread support (C11)

Technical Specifications

 

Thread support library

Threads
thrd_create thrd_equal thrd_current thrd_sleep thrd_yield thrd_exit	thrd_detach thrd_join thrd_successthrd_timedoutthrd_busythrd_nomemthrd_error
Mutual exclusion
mtx_init mtx_lock mtx_timedlock mtx_trylock call_once	mtx_unlock mtx_destroy mtx_plainmtx_recursivemtx_timed
Condition variables
cnd_init cnd_signal cnd_broadcast	cnd_wait cnd_timedwait cnd_destroy
Thread-local storage
thread_local TSS_DTOR_ITERATIONS tss_create	tss_get tss_set tss_delete

 

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

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

Parameters

(none)

Return value

(none)

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.

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 {
        thrd_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

References

• C11 standard (ISO/IEC 9899:2011):

• 7.26.5.8 The thrd_yield function (p: 385)

See also

thrd_sleep (C11)	suspends execution of the calling thread for the given period of time (function)
C++ documentation for yield