freebsd-dev/lib/libkse/thread/thr_kern.c

/*
 * Copyright (c) 1995-1998 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 <errno.h>
#include <poll.h>
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>
#include <unistd.h>
#include <sys/param.h>
#include <sys/types.h>
#include <sys/signalvar.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/socket.h>
#include <sys/uio.h>
#include <sys/syscall.h>
#include <fcntl.h>
#include <pthread.h>
#include "thr_private.h"

/* #define DEBUG_THREAD_KERN */
#ifdef DEBUG_THREAD_KERN
#define DBG_MSG		stdout_debug
#else
#define DBG_MSG(x...)
#endif

/* Static function prototype definitions: */
static void
thread_kern_idle(void);

static void
dequeue_signals(void);

static inline void
thread_run_switch_hook(pthread_t thread_out, pthread_t thread_in);

/* Static variables: */
static int	last_tick = 0;

void
_thread_kern_sched(void)
{
	struct pthread	*curthread = _get_curthread();

	/*
	 * Flag the pthread kernel as executing scheduler code
	 * to avoid a scheduler signal from interrupting this
	 * execution and calling the scheduler again.
	 */
	_thread_kern_in_sched = 1;

	/* Switch into the scheduler's context. */
	swapcontext(&curthread->ctx, &_thread_kern_sched_ctx);
	DBG_MSG("Returned from swapcontext, thread %p\n", curthread);

	/*
	 * This point is reached when swapcontext() is called
	 * to restore the state of a thread.
	 *
	 * This is the normal way out of the scheduler.
	 */
	_thread_kern_in_sched = 0;

	if (curthread->sig_defer_count == 0) {
		if (((curthread->cancelflags &
		    PTHREAD_AT_CANCEL_POINT) == 0) &&
		    ((curthread->cancelflags &
		    PTHREAD_CANCEL_ASYNCHRONOUS) != 0))
			/*
			 * Stick a cancellation point at the
			 * start of each async-cancellable
			 * thread's resumption.
			 *
			 * We allow threads woken at cancel
			 * points to do their own checks.
			 */
			pthread_testcancel();
	}

	if (_sched_switch_hook != NULL) {
		/* Run the installed switch hook: */
		thread_run_switch_hook(_last_user_thread, curthread);
	}
}

void
_thread_kern_scheduler(void)
{
	struct timespec	ts;
	struct timeval	tv;
	struct pthread	*curthread = _get_curthread();
	pthread_t	pthread, pthread_h;
	unsigned int	current_tick;
	int		add_to_prioq;

	/*
	 * Enter a scheduling loop that finds the next thread that is
	 * ready to run. This loop completes when there are no more threads
	 * in the global list. It is interrupted each time a thread is
	 * scheduled, but will continue when we return.
	 */
	while (!(TAILQ_EMPTY(&_thread_list))) {

		/* If the currently running thread is a user thread, save it: */
		if ((curthread->flags & PTHREAD_FLAGS_PRIVATE) == 0)
			_last_user_thread = curthread;

		/* Get the current time of day: */
		GET_CURRENT_TOD(tv);
		TIMEVAL_TO_TIMESPEC(&tv, &ts);
		current_tick = _sched_ticks;

		add_to_prioq = 0;
		if (curthread != &_thread_kern_thread) {
			/*
			 * This thread no longer needs to yield the CPU.
			 */
			if (curthread->state != PS_RUNNING) {
				/*
				 * Save the current time as the time that the
				 * thread became inactive:
				 */
				curthread->last_inactive = (long)current_tick;
				if (curthread->last_inactive <
				    curthread->last_active) {
					/* Account for a rollover: */
					curthread->last_inactive =+
					    UINT_MAX + 1;
				}
			}

			/*
			 * Place the currently running thread into the
			 * appropriate queue(s).
			 */
			switch (curthread->state) {
			case PS_DEAD:
			case PS_STATE_MAX: /* to silence -Wall */
			case PS_SUSPENDED:
				/*
				 * Dead and suspended threads are not placed
				 * in any queue:
				 */
				break;

			case PS_RUNNING:
				/*
				 * Runnable threads can't be placed in the
				 * priority queue until after waiting threads
				 * are polled (to preserve round-robin
				 * scheduling).
				 */
				add_to_prioq = 1;
				break;

			/*
			 * States which do not depend on file descriptor I/O
			 * operations or timeouts:
			 */
			case PS_DEADLOCK:
			case PS_JOIN:
			case PS_MUTEX_WAIT:
			case PS_WAIT_WAIT:
				/* No timeouts for these states: */
				curthread->wakeup_time.tv_sec = -1;
				curthread->wakeup_time.tv_nsec = -1;

				/* Restart the time slice: */
				curthread->slice_usec = -1;

				/* Insert into the waiting queue: */
				PTHREAD_WAITQ_INSERT(curthread);
				break;

			/* States which can timeout: */
			case PS_COND_WAIT:
			case PS_SLEEP_WAIT:
				/* Restart the time slice: */
				curthread->slice_usec = -1;

				/* Insert into the waiting queue: */
				PTHREAD_WAITQ_INSERT(curthread);
				break;
	
			/* States that require periodic work: */
			case PS_SPINBLOCK:
				/* No timeouts for this state: */
				curthread->wakeup_time.tv_sec = -1;
				curthread->wakeup_time.tv_nsec = -1;

				/* Increment spinblock count: */
				_spinblock_count++;

				/* FALLTHROUGH */
			}
		}

		last_tick = current_tick;

		/*
		 * Wake up threads that have timedout.  This has to be
		 * done after polling in case a thread does a poll or
		 * select with zero time.
		 */
		PTHREAD_WAITQ_SETACTIVE();
		while (((pthread = TAILQ_FIRST(&_waitingq)) != NULL) &&
		    (pthread->wakeup_time.tv_sec != -1) &&
		    (((pthread->wakeup_time.tv_sec == 0) &&
		    (pthread->wakeup_time.tv_nsec == 0)) ||
		    (pthread->wakeup_time.tv_sec < ts.tv_sec) ||
		    ((pthread->wakeup_time.tv_sec == ts.tv_sec) &&
		    (pthread->wakeup_time.tv_nsec <= ts.tv_nsec)))) {
			/*
			 * Remove this thread from the waiting queue
			 * (and work queue if necessary) and place it
			 * in the ready queue.
			 */
			PTHREAD_WAITQ_CLEARACTIVE();
			if (pthread->flags & PTHREAD_FLAGS_IN_WORKQ)
				PTHREAD_WORKQ_REMOVE(pthread);
			PTHREAD_NEW_STATE(pthread, PS_RUNNING);
			PTHREAD_WAITQ_SETACTIVE();
			/*
			 * Flag the timeout in the thread structure:
			 */
			pthread->timeout = 1;
		}
		PTHREAD_WAITQ_CLEARACTIVE();

		/*
		 * Check to see if the current thread needs to be added
		 * to the priority queue:
		 */
		if (add_to_prioq != 0) {
			/*
			 * Save the current time as the time that the
			 * thread became inactive:
			 */
			current_tick = _sched_ticks;
			curthread->last_inactive = (long)current_tick;
			if (curthread->last_inactive <
			    curthread->last_active) {
				/* Account for a rollover: */
				curthread->last_inactive =+ UINT_MAX + 1;
			}

			if ((curthread->slice_usec != -1) &&
		 	   (curthread->attr.sched_policy != SCHED_FIFO)) {
				/*
				 * Accumulate the number of microseconds for
				 * which the current thread has run:
				 */
				curthread->slice_usec +=
				    (curthread->last_inactive -
				    curthread->last_active) *
				    (long)_clock_res_usec;
				/* Check for time quantum exceeded: */
				if (curthread->slice_usec > TIMESLICE_USEC)
					curthread->slice_usec = -1;
			}

			if (curthread->slice_usec == -1) {
				/*
				 * The thread exceeded its time
				 * quantum or it yielded the CPU;
				 * place it at the tail of the
				 * queue for its priority.
				 */
				PTHREAD_PRIOQ_INSERT_TAIL(curthread);
			} else {
				/*
				 * The thread hasn't exceeded its
				 * interval.  Place it at the head
				 * of the queue for its priority.
				 */
				PTHREAD_PRIOQ_INSERT_HEAD(curthread);
			}
		}

		/*
		 * Get the highest priority thread in the ready queue.
		 */
		pthread_h = PTHREAD_PRIOQ_FIRST();

		/* Check if there are no threads ready to run: */
		if (pthread_h == NULL) {
			/*
			 * Lock the pthread kernel by changing the pointer to
			 * the running thread to point to the global kernel
			 * thread structure:
			 */
			_set_curthread(&_thread_kern_thread);
			curthread = &_thread_kern_thread;

			DBG_MSG("No runnable threads, using kernel thread %p\n",
			    curthread);

			/*
			 * There are no threads ready to run, so wait until
			 * something happens that changes this condition:
			 */
			thread_kern_idle();

			/*
			 * This process' usage will likely be very small
			 * while waiting in a poll.  Since the scheduling
			 * clock is based on the profiling timer, it is
			 * unlikely that the profiling timer will fire
			 * and update the time of day.  To account for this,
			 * get the time of day after polling with a timeout.
			 */
			gettimeofday((struct timeval *) &_sched_tod, NULL);
			
			/* Check once more for a runnable thread: */
			pthread_h = PTHREAD_PRIOQ_FIRST();
		}

		if (pthread_h != NULL) {
			/* Remove the thread from the ready queue: */
			PTHREAD_PRIOQ_REMOVE(pthread_h);

			/* Make the selected thread the current thread: */
			_set_curthread(pthread_h);
			curthread = pthread_h;

			/*
			 * Save the current time as the time that the thread
			 * became active:
			 */
			current_tick = _sched_ticks;
			curthread->last_active = (long) current_tick;

			/*
			 * Check if this thread is running for the first time
			 * or running again after using its full time slice
			 * allocation:
			 */
			if (curthread->slice_usec == -1) {
				/* Reset the accumulated time slice period: */
				curthread->slice_usec = 0;
			}

			/*
			 * If we had a context switch, run any
			 * installed switch hooks.
			 */
			if ((_sched_switch_hook != NULL) &&
			    (_last_user_thread != curthread)) {
				thread_run_switch_hook(_last_user_thread,
				    curthread);
			}
			/*
			 * Continue the thread at its current frame:
			 */
			swapcontext(&_thread_kern_sched_ctx, &curthread->ctx);
		}
	}

	/* There are no more threads, so exit this process: */
	exit(0);
}

void
_thread_kern_sched_state(enum pthread_state state, char *fname, int lineno)
{
	struct pthread	*curthread = _get_curthread();

	/*
	 * Flag the pthread kernel as executing scheduler code
	 * to avoid a scheduler signal from interrupting this
	 * execution and calling the scheduler again.
	 */
	_thread_kern_in_sched = 1;

	/* Change the state of the current thread: */
	curthread->state = state;
	curthread->fname = fname;
	curthread->lineno = lineno;

	/* Schedule the next thread that is ready: */
	_thread_kern_sched();
}

void
_thread_kern_sched_state_unlock(enum pthread_state state,
    spinlock_t *lock, char *fname, int lineno)
{
	struct pthread	*curthread = _get_curthread();

	/*
	 * Flag the pthread kernel as executing scheduler code
	 * to avoid a scheduler signal from interrupting this
	 * execution and calling the scheduler again.
	 */
	_thread_kern_in_sched = 1;

	/* Change the state of the current thread: */
	curthread->state = state;
	curthread->fname = fname;
	curthread->lineno = lineno;

	_SPINUNLOCK(lock);

	/* Schedule the next thread that is ready: */
	_thread_kern_sched();
}

static void
thread_kern_idle()
{
	int             i, found;
	int		kern_pipe_added = 0;
	int             nfds = 0;
	int		timeout_ms = 0;
	struct pthread	*pthread;
	struct timespec ts;
	struct timeval  tv;

	/* Get the current time of day: */
	GET_CURRENT_TOD(tv);
	TIMEVAL_TO_TIMESPEC(&tv, &ts);

	pthread = TAILQ_FIRST(&_waitingq);

	if ((pthread == NULL) || (pthread->wakeup_time.tv_sec == -1)) {
		/*
		 * Either there are no threads in the waiting queue,
		 * or there are no threads that can timeout.
		 */
		PANIC("Would idle forever");
	}
	else if (pthread->wakeup_time.tv_sec - ts.tv_sec > 60000)
		/* Limit maximum timeout to prevent rollover. */
		timeout_ms = 60000;
	else {
		/*
		 * Calculate the time left for the next thread to
		 * timeout:
		 */
		timeout_ms = ((pthread->wakeup_time.tv_sec - ts.tv_sec) *
		    1000) + ((pthread->wakeup_time.tv_nsec - ts.tv_nsec) /
		    1000000);
		/*
		 * Only idle if we would be.
		 */
		if (timeout_ms <= 0)
			return;
	}

	/*
	 * Check for a thread that became runnable due to a signal:
	 */
	if (PTHREAD_PRIOQ_FIRST() != NULL) {
		/*
		 * Since there is at least one runnable thread,
		 * disable the wait.
		 */
		timeout_ms = 0;
	}

	/*
	 * Idle.
	 */
	__sys_poll(NULL, 0, timeout_ms);

	if (_spinblock_count != 0) {
		/*
		 * Enter a loop to look for threads waiting on a spinlock
		 * that is now available.
		 */
		PTHREAD_WAITQ_SETACTIVE();
		TAILQ_FOREACH(pthread, &_workq, qe) {
			if (pthread->state == PS_SPINBLOCK) {
				/*
				 * If the lock is available, let the thread run.
				 */
				if (pthread->data.spinlock->access_lock == 0) {
					PTHREAD_WAITQ_CLEARACTIVE();
					PTHREAD_WORKQ_REMOVE(pthread);
					PTHREAD_NEW_STATE(pthread,PS_RUNNING);
					PTHREAD_WAITQ_SETACTIVE();

					/*
					 * One less thread in a spinblock state:
					 */
					_spinblock_count--;
				}
			}
		}
		PTHREAD_WAITQ_CLEARACTIVE();
	}
}

void
_thread_kern_set_timeout(const struct timespec * timeout)
{
	struct pthread	*curthread = _get_curthread();
	struct timespec current_time;
	struct timeval  tv;

	/* Reset the timeout flag for the running thread: */
	curthread->timeout = 0;

	/* Check if the thread is to wait forever: */
	if (timeout == NULL) {
		/*
		 * Set the wakeup time to something that can be recognised as
		 * different to an actual time of day:
		 */
		curthread->wakeup_time.tv_sec = -1;
		curthread->wakeup_time.tv_nsec = -1;
	}
	/* Check if no waiting is required: */
	else if (timeout->tv_sec == 0 && timeout->tv_nsec == 0) {
		/* Set the wake up time to 'immediately': */
		curthread->wakeup_time.tv_sec = 0;
		curthread->wakeup_time.tv_nsec = 0;
	} else {
		/* Get the current time: */
		GET_CURRENT_TOD(tv);
		TIMEVAL_TO_TIMESPEC(&tv, &current_time);

		/* Calculate the time for the current thread to wake up: */
		curthread->wakeup_time.tv_sec = current_time.tv_sec + timeout->tv_sec;
		curthread->wakeup_time.tv_nsec = current_time.tv_nsec + timeout->tv_nsec;

		/* Check if the nanosecond field needs to wrap: */
		if (curthread->wakeup_time.tv_nsec >= 1000000000) {
			/* Wrap the nanosecond field: */
			curthread->wakeup_time.tv_sec += 1;
			curthread->wakeup_time.tv_nsec -= 1000000000;
		}
	}
}

void
_thread_kern_sig_defer(void)
{
	struct pthread	*curthread = _get_curthread();

	/* Allow signal deferral to be recursive. */
	curthread->sig_defer_count++;
}

void
_thread_kern_sig_undefer(void)
{
	struct pthread	*curthread = _get_curthread();

	/*
	 * Perform checks to yield only if we are about to undefer
	 * signals.
	 */
	if (curthread->sig_defer_count > 1) {
		/* Decrement the signal deferral count. */
		curthread->sig_defer_count--;
	}
	else if (curthread->sig_defer_count == 1) {
		/* Reenable signals: */
		curthread->sig_defer_count = 0;

		/*
		 * Check for asynchronous cancellation before delivering any
		 * pending signals:
		 */
		if (((curthread->cancelflags & PTHREAD_AT_CANCEL_POINT) == 0) &&
		    ((curthread->cancelflags & PTHREAD_CANCEL_ASYNCHRONOUS) != 0))
			pthread_testcancel();
	}
}

static inline void
thread_run_switch_hook(pthread_t thread_out, pthread_t thread_in)
{
	pthread_t tid_out = thread_out;
	pthread_t tid_in = thread_in;

	if ((tid_out != NULL) &&
	    (tid_out->flags & PTHREAD_FLAGS_PRIVATE) != 0)
		tid_out = NULL;
	if ((tid_in != NULL) &&
	    (tid_in->flags & PTHREAD_FLAGS_PRIVATE) != 0)
		tid_in = NULL;

	if ((_sched_switch_hook != NULL) && (tid_out != tid_in)) {
		/* Run the scheduler switch hook: */
		_sched_switch_hook(tid_out, tid_in);
	}
}

struct pthread *
_get_curthread(void)
{
	if (_thread_initial == NULL)
		_thread_init();

	return (_thread_run);
}

void
_set_curthread(struct pthread *newthread)
{
	_thread_run = newthread;
}