freebsd-nq/lib/libkse/thread/thr_yield.c
Daniel Eischen fd626336fd Add a method of yielding the current thread with the scheduler
lock held (_thr_sched_switch_unlocked()) and use this to avoid
dropping the scheduler lock and having the scheduler retake the
same lock again.

Add a better way of detecting if a low-level lock is in use.

When switching out a thread due to blocking in the UTS, don't
switch to the KSE's scheduler stack only to switch back to
another thread.  If possible switch to the new thread directly
from the old thread and avoid the overhead of the extra
context switch.

Check for pending signals on a thread when entering the scheduler
and add them to the threads signal frame.  This includes some
other minor signal fixes.

Most of this was a joint effor between davidxu and myself.

Reviewed by:	davidxu
Approved by:	re@ (blanket for libpthread)
2003-05-16 19:58:30 +00:00

66 lines
2.4 KiB
C

/*
* Copyright (c) 1995 John Birrell <jb@cimlogic.com.au>.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by John Birrell.
* 4. Neither the name of the author nor the names of any co-contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $FreeBSD$
*/
#include <pthread.h>
#include "thr_private.h"
__weak_reference(_sched_yield, sched_yield);
__weak_reference(_pthread_yield, pthread_yield);
int
_sched_yield(void)
{
struct pthread *curthread = _get_curthread();
/* Reset the accumulated time slice value for the current thread: */
curthread->slice_usec = -1;
/* Schedule the next thread: */
_thr_sched_switch(curthread);
/* Always return no error. */
return(0);
}
/* Draft 4 yield */
void
_pthread_yield(void)
{
struct pthread *curthread = _get_curthread();
/* Reset the accumulated time slice value for the current thread: */
curthread->slice_usec = -1;
/* Schedule the next thread: */
_thr_sched_switch(curthread);
}