Discourage sched_yield(2)

Hi Andrew,

Here's a patch set for discouraging sched_yield(2). See the formatted page at the bottom. I also updated some POSIX historic detail.

Cheers,
Alex

Alejandro Colomar (3):
sched_yield.2: HISTORY: POSIX.1-2008 makes this non-optional sched_yield.2: NOTES: Remove misleading sentence sched_yield.2: Rename NOTES to CAVEATS, and reorder contents

 man2/sched_yield.2 | 41 +++++++++++++++++++----------------------
 1 file changed, 19 insertions(+), 22 deletions(-)

---

$ MANWIDTH=72 man ./man2/sched_yield.2 | cat
sched_yield(2)            System Calls Manual           sched_yield(2)

NAME
sched_yield - yield the processor

LIBRARY
Standard C library (libc, -lc)

SYNOPSIS

       #include <sched.h>

       int sched_yield(void);

DESCRIPTION
sched_yield() causes the calling thread to relinquish the CPU. The thread is moved to the end of the queue for its static pri‐ ority and a new thread gets to run.

RETURN VALUE
On success, sched_yield() returns 0. On error, -1 is returned, and errno is set to indicate the error.

ERRORS
In the Linux implementation, sched_yield() always succeeds.

STANDARDS

       POSIX.1‐2008.

HISTORY
POSIX.1‐2001 (but optional). POSIX.1‐2008.

Before POSIX.1‐2008, systems on which sched_yield() is avail‐ able defined _POSIX_PRIORITY_SCHEDULING in <unistd.h>.

CAVEATS
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.

If the calling thread is the only thread in the highest prior‐ ity list at that time, it will continue to run after a call to sched_yield().

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 unnec‐ essary context switches, which will degrade system performance.

SEE ALSO

       sched(7)

Linux man‐pages (unreleased) (date) sched_yield(2)

2.40.1