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diff --git a/devdocs/c/thread%2Fthrd_yield.html b/devdocs/c/thread%2Fthrd_yield.html new file mode 100644 index 00000000..7eb8bcad --- /dev/null +++ b/devdocs/c/thread%2Fthrd_yield.html @@ -0,0 +1,52 @@ + <h1 id="firstHeading" class="firstHeading">thrd_yield</h1> <table class="t-dcl-begin"> <tr class="t-dsc-header"> <th> Defined in header <code><threads.h></code> </th> <th> </th> <th> </th> </tr> <tr class="t-dcl t-since-c11"> <td> <pre data-language="c">void thrd_yield(void);</pre> +</td> <td class="t-dcl-nopad"> </td> <td> <span class="t-mark-rev t-since-c11">(since C11)</span> </td> </tr> </table> <p>Provides a hint to the implementation to reschedule the execution of threads, allowing other threads to run.</p> +<h3 id="Parameters"> Parameters</h3> <p>(none)</p> +<h3 id="Return_value"> Return value</h3> <p>(none)</p> +<h3 id="Notes"> Notes</h3> <p>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 (<code>SCHED_FIFO</code> 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, <code>yield</code> has no effect).</p> +<p>The POSIX equivalent of this function is <a rel="nofollow" class="external text" href="http://pubs.opengroup.org/onlinepubs/9699919799/functions/sched_yield.html"><code>sched_yield</code></a>.</p> +<h3 id="Example"> Example</h3> <div class="t-example"> <div class="c source-c"><pre data-language="c">#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)); +}</pre></div> <p>Possible output:</p> +<div class="text source-text"><pre data-language="c">Waited for 100.344 us</pre></div> </div> <h3 id="References"> References</h3> <ul> +<li> C17 standard (ISO/IEC 9899:2018): </li> +<ul><li> 7.26.5.8 The thrd_yield function (p: 281) </li></ul> +<li> C11 standard (ISO/IEC 9899:2011): </li> +<ul><li> 7.26.5.8 The thrd_yield function (p: 385) </li></ul> +</ul> <h3 id="See_also"> See also</h3> <table class="t-dsc-begin"> <tr class="t-dsc"> <td> <div><a href="thrd_sleep" title="c/thread/thrd sleep"> <span class="t-lines"><span>thrd_sleep</span></span></a></div> +<div><span class="t-lines"><span><span class="t-mark-rev t-since-c11">(C11)</span></span></span></div> </td> <td> suspends execution of the calling thread for the given period of time <br> <span class="t-mark">(function)</span> </td> +</tr> <tr class="t-dsc"> <td colspan="2"> <span><a href="https://en.cppreference.com/w/cpp/thread/yield" title="cpp/thread/yield">C++ documentation</a></span> for <code>yield</code> </td> +</tr> </table> <div class="_attribution"> + <p class="_attribution-p"> + © cppreference.com<br>Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.<br> + <a href="https://en.cppreference.com/w/c/thread/thrd_yield" class="_attribution-link">https://en.cppreference.com/w/c/thread/thrd_yield</a> + </p> +</div> |