2. System calls (functions provided by the kernel)
SCHED_YIELDSection: Linux Programmer's Manual (2)
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NAMEsched_yield - yield the processor
DESCRIPTIONsched_yield() causes the calling thread to relinquish the CPU. The thread is moved to the end of the queue for its static priority and a new thread gets to run.
RETURN VALUEOn success, sched_yield() returns 0. On error, -1 is returned, and errno is set appropriately.
ERRORSIn the Linux implementation, sched_yield() always succeeds.
CONFORMING TOPOSIX.1-2001, POSIX.1-2008.
NOTESIf the calling thread is the only thread in the highest priority list at that time, it will continue to run after a call to sched_yield().
POSIX systems on which sched_yield() is available define _POSIX_PRIORITY_SCHEDULING in <unistd.h>.
Strategic calls to sched_yield() can improve performance by giving other threads or processes a chance to run when (heavily) contended resources (e.g., mutexes) have been released by the caller. Avoid calling sched_yield() unnecessarily or inappropriately (e.g., when resources needed by other schedulable threads are still held by the caller), since doing so will result in unnecessary context switches, which will degrade system performance.
sched_yield() is intended for use with real-time scheduling policies (i.e., SCHED_FIFO or SCHED_RR). Use of sched_yield() with nondeterministic scheduling policies such as SCHED_OTHER is unspecified and very likely means your application design is broken.
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