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freebsd-nq/lib/libpthread/thread/thr_kern.c
Dmitrij Tejblum 4b12016bab Fix some bugs in pthread scheduler: 
make pthread_yield() more reliable,
  threads always (I hope) preempted at least every 0.1 sec, as intended.

PR:		bin/7744
Submitted by:	"Richard Seaman, Jr." <dick@tar.com>
1998-10-09 19:01:30 +00:00

1308 lines
33 KiB
C
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/*
* 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 REGENTS 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.
*
* $Id: uthread_kern.c,v 1.13 1998/09/30 06:36:56 jb Exp $
*
*/
#include <errno.h>
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>
#include <unistd.h>
#include <setjmp.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/socket.h>
#include <sys/uio.h>
#include <sys/syscall.h>
#include <fcntl.h>
#ifdef _THREAD_SAFE
#include <pthread.h>
#include "pthread_private.h"
/* Static function prototype definitions: */
static void
_thread_kern_select(int wait_reqd);
void
_thread_kern_sched(struct sigcontext * scp)
{
#ifndef __alpha__
char *fdata;
#endif
int prio = -1;
pthread_t pthread;
pthread_t pthread_h = NULL;
pthread_t pthread_s = NULL;
struct itimerval itimer;
struct timespec ts;
struct timespec ts1;
struct timeval tv;
struct timeval tv1;
/*
* 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;
/* Check if this function was called from the signal handler: */
if (scp != NULL) {
/*
* Copy the signal context to the current thread's jump
* buffer:
*/
memcpy(&_thread_run->saved_sigcontext, scp, sizeof(_thread_run->saved_sigcontext));
#ifndef __alpha__
/* Point to the floating point data in the running thread: */
fdata = _thread_run->saved_fp;
/* Save the floating point data: */
__asm__("fnsave %0": :"m"(*fdata));
#endif
/* Flag the signal context as the last state saved: */
_thread_run->sig_saved = 1;
}
/* Save the state of the current thread: */
else if (setjmp(_thread_run->saved_jmp_buf) != 0) {
/*
* This point is reached when a longjmp() is called to
* restore the state of a thread.
*
* This is the normal way out of the scheduler.
*/
_thread_kern_in_sched = 0;
/*
* There might be pending signals for this thread, so
* dispatch any that aren't blocked:
*/
_dispatch_signals();
return;
} else
/* Flag the jump buffer was the last state saved: */
_thread_run->sig_saved = 0;
/*
* Enter a the 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 or when a thread has its state restored by
* either a sigreturn (if the state was saved as a sigcontext) or a
* longjmp (if the state was saved by a setjmp).
*/
while (_thread_link_list != NULL) {
/* Get the current time of day: */
gettimeofday(&tv, NULL);
TIMEVAL_TO_TIMESPEC(&tv, &ts);
/*
* Poll file descriptors to update the state of threads
* waiting on file I/O where data may be available:
*/
_thread_kern_select(0);
/*
* Enter a loop to look for sleeping threads that are ready:
*/
for (pthread = _thread_link_list; pthread != NULL;
pthread = pthread->nxt) {
/* Check if this thread is to timeout: */
if (pthread->state == PS_COND_WAIT ||
pthread->state == PS_SLEEP_WAIT ||
pthread->state == PS_FDR_WAIT ||
pthread->state == PS_FDW_WAIT ||
pthread->state == PS_SELECT_WAIT) {
/* Check if this thread is to wait forever: */
if (pthread->wakeup_time.tv_sec == -1) {
}
/*
* Check if this thread is to wakeup
* immediately or if it is past its wakeup
* time:
*/
else if ((pthread->wakeup_time.tv_sec == 0 &&
pthread->wakeup_time.tv_nsec == 0) ||
(ts.tv_sec > pthread->wakeup_time.tv_sec) ||
((ts.tv_sec == pthread->wakeup_time.tv_sec) &&
(ts.tv_nsec >= pthread->wakeup_time.tv_nsec))) {
/*
* Check if this thread is waiting on
* select:
*/
if (pthread->state == PS_SELECT_WAIT) {
/*
* The select has timed out,
* so zero the file
* descriptor sets:
*/
FD_ZERO(&pthread->data.select_data->readfds);
FD_ZERO(&pthread->data.select_data->writefds);
FD_ZERO(&pthread->data.select_data->exceptfds);
pthread->data.select_data->nfds = 0;
}
/*
* Return an error as an interrupted
* wait:
*/
_thread_seterrno(pthread, EINTR);
/*
* Flag the timeout in the thread
* structure:
*/
pthread->timeout = 1;
/*
* Change the threads state to allow
* it to be restarted:
*/
PTHREAD_NEW_STATE(pthread,PS_RUNNING);
}
}
}
/* Check if there is a current thread: */
if (_thread_run != &_thread_kern_thread) {
/*
* Save the current time as the time that the thread
* became inactive:
*/
_thread_run->last_inactive.tv_sec = tv.tv_sec;
_thread_run->last_inactive.tv_usec = tv.tv_usec;
/*
* Accumulate the number of microseconds that this
* thread has run for:
*/
if (_thread_run->slice_usec != -1) {
_thread_run->slice_usec += (_thread_run->last_inactive.tv_sec -
_thread_run->last_active.tv_sec) * 1000000 +
_thread_run->last_inactive.tv_usec -
_thread_run->last_active.tv_usec;
}
/*
* Check if this thread has reached its allocated
* time slice period:
*/
if (_thread_run->slice_usec > TIMESLICE_USEC) {
/*
* Flag the allocated time slice period as
* up:
*/
_thread_run->slice_usec = -1;
}
}
/* Check if an incremental priority update is required: */
if (((tv.tv_sec - kern_inc_prio_time.tv_sec) * 1000000 +
tv.tv_usec - kern_inc_prio_time.tv_usec) > INC_PRIO_USEC) {
/*
* Enter a loop to look for run-enabled threads that
* have not run since the last time that an
* incremental priority update was performed:
*/
for (pthread = _thread_link_list; pthread != NULL; pthread = pthread->nxt) {
/* Check if this thread is unable to run: */
if (pthread->state != PS_RUNNING) {
}
/*
* Check if the last time that this thread
* was run (as indicated by the last time it
* became inactive) is before the time that
* the last incremental priority check was
* made:
*/
else if (timercmp(&pthread->last_inactive, &kern_inc_prio_time, <)) {
/*
* Increment the incremental priority
* for this thread in the hope that
* it will eventually get a chance to
* run:
*/
(pthread->inc_prio)++;
}
}
/* Save the new incremental priority update time: */
kern_inc_prio_time.tv_sec = tv.tv_sec;
kern_inc_prio_time.tv_usec = tv.tv_usec;
}
/*
* Enter a loop to look for the first thread of the highest
* priority that is ready to run:
*/
for (pthread = _thread_link_list; pthread != NULL; pthread = pthread->nxt) {
/* Check if the current thread is unable to run: */
if (pthread->state != PS_RUNNING) {
}
/*
* Check if no run-enabled thread has been seen or if
* the current thread has a priority higher than the
* highest seen so far:
*/
else if (pthread_h == NULL || (pthread->pthread_priority + pthread->inc_prio) > prio) {
/*
* Save this thread as the highest priority
* thread seen so far:
*/
pthread_h = pthread;
prio = pthread->pthread_priority + pthread->inc_prio;
}
}
/*
* Enter a loop to look for a thread that: 1. Is run-enabled.
* 2. Has the required agregate priority. 3. Has not been
* allocated its allocated time slice. 4. Became inactive
* least recently.
*/
for (pthread = _thread_link_list; pthread != NULL; pthread = pthread->nxt) {
/* Check if the current thread is unable to run: */
if (pthread->state != PS_RUNNING) {
/* Ignore threads that are not ready to run. */
}
/*
* Check if the current thread as an agregate
* priority not equal to the highest priority found
* above:
*/
else if ((pthread->pthread_priority + pthread->inc_prio) != prio) {
/*
* Ignore threads which have lower agregate
* priority.
*/
}
/*
* Check if the current thread reached its time slice
* allocation last time it ran (or if it has not run
* yet):
*/
else if (pthread->slice_usec == -1) {
}
/*
* Check if an eligible thread has not been found
* yet, or if the current thread has an inactive time
* earlier than the last one seen:
*/
else if (pthread_s == NULL || timercmp(&pthread->last_inactive, &tv1, <)) {
/*
* Save the pointer to the current thread as
* the most eligible thread seen so far:
*/
pthread_s = pthread;
/*
* Save the time that the selected thread
* became inactive:
*/
tv1.tv_sec = pthread->last_inactive.tv_sec;
tv1.tv_usec = pthread->last_inactive.tv_usec;
}
}
/*
* Check if no thread was selected according to incomplete
* time slice allocation:
*/
if (pthread_s == NULL) {
/*
* Enter a loop to look for any other thread that: 1.
* Is run-enabled. 2. Has the required agregate
* priority. 3. Became inactive least recently.
*/
for (pthread = _thread_link_list; pthread != NULL; pthread = pthread->nxt) {
/*
* Check if the current thread is unable to
* run:
*/
if (pthread->state != PS_RUNNING) {
/*
* Ignore threads that are not ready
* to run.
*/
}
/*
* Check if the current thread as an agregate
* priority not equal to the highest priority
* found above:
*/
else if ((pthread->pthread_priority + pthread->inc_prio) != prio) {
/*
* Ignore threads which have lower
* agregate priority.
*/
}
/*
* Check if an eligible thread has not been
* found yet, or if the current thread has an
* inactive time earlier than the last one
* seen:
*/
else if (pthread_s == NULL || timercmp(&pthread->last_inactive, &tv1, <)) {
/*
* Save the pointer to the current
* thread as the most eligible thread
* seen so far:
*/
pthread_s = pthread;
/*
* Save the time that the selected
* thread became inactive:
*/
tv1.tv_sec = pthread->last_inactive.tv_sec;
tv1.tv_usec = pthread->last_inactive.tv_usec;
}
}
}
/* Check if there are no threads ready to run: */
if (pthread_s == NULL) {
/*
* Lock the pthread kernel by changing the pointer to
* the running thread to point to the global kernel
* thread structure:
*/
_thread_run = &_thread_kern_thread;
/*
* There are no threads ready to run, so wait until
* something happens that changes this condition:
*/
_thread_kern_select(1);
} else {
/* Make the selected thread the current thread: */
_thread_run = pthread_s;
/*
* Save the current time as the time that the thread
* became active:
*/
_thread_run->last_active.tv_sec = tv.tv_sec;
_thread_run->last_active.tv_usec = tv.tv_usec;
/*
* Check if this thread is running for the first time
* or running again after using its full time slice
* allocation:
*/
if (_thread_run->slice_usec == -1) {
/* Reset the accumulated time slice period: */
_thread_run->slice_usec = 0;
}
/*
* Reset the incremental priority now that this
* thread has been given the chance to run:
*/
_thread_run->inc_prio = 0;
/* Check if there is more than one thread: */
if (_thread_run != _thread_link_list || _thread_run->nxt != NULL) {
/*
* Define the maximum time before a SIGVTALRM
* is required:
*/
itimer.it_value.tv_sec = 0;
itimer.it_value.tv_usec = TIMESLICE_USEC;
/*
* The interval timer is not reloaded when it
* times out. The interval time needs to be
* calculated every time.
*/
itimer.it_interval.tv_sec = 0;
itimer.it_interval.tv_usec = 0;
/*
* Enter a loop to look for threads waiting
* for a time:
*/
for (pthread = _thread_link_list; pthread != NULL; pthread = pthread->nxt) {
/*
* Check if this thread is to
* timeout:
*/
if (pthread->state == PS_COND_WAIT ||
pthread->state == PS_SLEEP_WAIT ||
pthread->state == PS_FDR_WAIT ||
pthread->state == PS_FDW_WAIT ||
pthread->state == PS_SELECT_WAIT) {
/*
* Check if this thread is to
* wait forever:
*/
if (pthread->wakeup_time.tv_sec == -1) {
}
/*
* Check if this thread is to
* wakeup immediately:
*/
else if (pthread->wakeup_time.tv_sec == 0 &&
pthread->wakeup_time.tv_nsec == 0) {
}
/*
* Check if the current time
* is after the wakeup time:
*/
else if ((ts.tv_sec > pthread->wakeup_time.tv_sec) ||
((ts.tv_sec == pthread->wakeup_time.tv_sec) &&
(ts.tv_nsec > pthread->wakeup_time.tv_nsec))) {
} else {
/*
* Calculate the time
* until this thread
* is ready, allowing
* for the clock
* resolution:
*/
ts1.tv_sec = pthread->wakeup_time.tv_sec - ts.tv_sec;
ts1.tv_nsec = pthread->wakeup_time.tv_nsec - ts.tv_nsec +
CLOCK_RES_NSEC;
/*
* Check for
* underflow of the
* nanosecond field:
*/
if (ts1.tv_nsec < 0) {
/*
* Allow for
* the
* underflow
* of the
* nanosecond
* field:
*/
ts1.tv_sec--;
ts1.tv_nsec += 1000000000;
}
/*
* Check for overflow
* of the nanosecond
* field:
*/
if (ts1.tv_nsec >= 1000000000) {
/*
* Allow for
* the
* overflow
* of the
* nanosecond
* field:
*/
ts1.tv_sec++;
ts1.tv_nsec -= 1000000000;
}
/*
* Convert the
* timespec structure
* to a timeval
* structure:
*/
TIMESPEC_TO_TIMEVAL(&tv, &ts1);
/*
* Check if the
* thread will be
* ready sooner than
* the earliest one
* found so far:
*/
if (timercmp(&tv, &itimer.it_value, <)) {
/*
* Update the
* time
* value:
*/
itimer.it_value.tv_sec = tv.tv_sec;
itimer.it_value.tv_usec = tv.tv_usec;
}
}
}
}
/*
* Start the interval timer for the
* calculated time interval:
*/
if (setitimer(ITIMER_VIRTUAL, &itimer, NULL) != 0) {
/*
* Cannot initialise the timer, so
* abort this process:
*/
PANIC("Cannot set virtual timer");
}
}
/* Check if a signal context was saved: */
if (_thread_run->sig_saved == 1) {
#ifndef __alpha__
/*
* Point to the floating point data in the
* running thread:
*/
fdata = _thread_run->saved_fp;
/* Restore the floating point state: */
__asm__("frstor %0": :"m"(*fdata));
#endif
/*
* Do a sigreturn to restart the thread that
* was interrupted by a signal:
*/
_thread_kern_in_sched = 0;
_thread_sys_sigreturn(&_thread_run->saved_sigcontext);
} else
/*
* Do a longjmp to restart the thread that
* was context switched out (by a longjmp to
* a different thread):
*/
longjmp(_thread_run->saved_jmp_buf, 1);
/* This point should not be reached. */
PANIC("Thread has returned from sigreturn or longjmp");
}
}
/* There are no more threads, so exit this process: */
exit(0);
}
void
_thread_kern_sched_state(enum pthread_state state, char *fname, int lineno)
{
/* Change the state of the current thread: */
_thread_run->state = state;
_thread_run->fname = fname;
_thread_run->lineno = lineno;
/* Schedule the next thread that is ready: */
_thread_kern_sched(NULL);
return;
}
static void
_thread_kern_select(int wait_reqd)
{
char bufr[128];
fd_set fd_set_except;
fd_set fd_set_read;
fd_set fd_set_write;
int count = 0;
int count_dec;
int found_one;
int i;
int nfds = -1;
int settimeout;
pthread_t pthread;
ssize_t num;
struct timespec ts;
struct timespec ts1;
struct timeval *p_tv;
struct timeval tv;
struct timeval tv1;
/* Zero the file descriptor sets: */
FD_ZERO(&fd_set_read);
FD_ZERO(&fd_set_write);
FD_ZERO(&fd_set_except);
/* Check if the caller wants to wait: */
if (wait_reqd) {
/*
* Add the pthread kernel pipe file descriptor to the read
* set:
*/
FD_SET(_thread_kern_pipe[0], &fd_set_read);
nfds = _thread_kern_pipe[0];
/* Get the current time of day: */
gettimeofday(&tv, NULL);
TIMEVAL_TO_TIMESPEC(&tv, &ts);
}
/* Initialise the time value structure: */
tv.tv_sec = 0;
tv.tv_usec = 0;
/*
* Enter a loop to process threads waiting on either file descriptors
* or times:
*/
for (pthread = _thread_link_list; pthread != NULL; pthread = pthread->nxt) {
/* Assume that this state does not time out: */
settimeout = 0;
/* Process according to thread state: */
switch (pthread->state) {
/*
* States which do not depend on file descriptor I/O
* operations or timeouts:
*/
case PS_DEAD:
case PS_FDLR_WAIT:
case PS_FDLW_WAIT:
case PS_FILE_WAIT:
case PS_JOIN:
case PS_MUTEX_WAIT:
case PS_RUNNING:
case PS_SIGTHREAD:
case PS_SIGWAIT:
case PS_STATE_MAX:
case PS_WAIT_WAIT:
case PS_SUSPENDED:
/* Nothing to do here. */
break;
/* File descriptor read wait: */
case PS_FDR_WAIT:
/* Add the file descriptor to the read set: */
FD_SET(pthread->data.fd.fd, &fd_set_read);
/*
* Check if this file descriptor is greater than any
* of those seen so far:
*/
if (pthread->data.fd.fd > nfds) {
/* Remember this file descriptor: */
nfds = pthread->data.fd.fd;
}
/* Increment the file descriptor count: */
count++;
/* This state can time out: */
settimeout = 1;
break;
/* File descriptor write wait: */
case PS_FDW_WAIT:
/* Add the file descriptor to the write set: */
FD_SET(pthread->data.fd.fd, &fd_set_write);
/*
* Check if this file descriptor is greater than any
* of those seen so far:
*/
if (pthread->data.fd.fd > nfds) {
/* Remember this file descriptor: */
nfds = pthread->data.fd.fd;
}
/* Increment the file descriptor count: */
count++;
/* This state can time out: */
settimeout = 1;
break;
/* States that time out: */
case PS_SLEEP_WAIT:
case PS_COND_WAIT:
/* Flag a timeout as required: */
settimeout = 1;
break;
/* Select wait: */
case PS_SELECT_WAIT:
/*
* Enter a loop to process each file descriptor in
* the thread-specific file descriptor sets:
*/
for (i = 0; i < pthread->data.select_data->nfds; i++) {
/*
* Check if this file descriptor is set for
* exceptions:
*/
if (FD_ISSET(i, &pthread->data.select_data->exceptfds)) {
/*
* Add the file descriptor to the
* exception set:
*/
FD_SET(i, &fd_set_except);
/*
* Increment the file descriptor
* count:
*/
count++;
/*
* Check if this file descriptor is
* greater than any of those seen so
* far:
*/
if (i > nfds) {
/*
* Remember this file
* descriptor:
*/
nfds = i;
}
}
/*
* Check if this file descriptor is set for
* write:
*/
if (FD_ISSET(i, &pthread->data.select_data->writefds)) {
/*
* Add the file descriptor to the
* write set:
*/
FD_SET(i, &fd_set_write);
/*
* Increment the file descriptor
* count:
*/
count++;
/*
* Check if this file descriptor is
* greater than any of those seen so
* far:
*/
if (i > nfds) {
/*
* Remember this file
* descriptor:
*/
nfds = i;
}
}
/*
* Check if this file descriptor is set for
* read:
*/
if (FD_ISSET(i, &pthread->data.select_data->readfds)) {
/*
* Add the file descriptor to the
* read set:
*/
FD_SET(i, &fd_set_read);
/*
* Increment the file descriptor
* count:
*/
count++;
/*
* Check if this file descriptor is
* greater than any of those seen so
* far:
*/
if (i > nfds) {
/*
* Remember this file
* descriptor:
*/
nfds = i;
}
}
}
/* This state can time out: */
settimeout = 1;
break;
}
/*
* Check if the caller wants to wait and if the thread state
* is one that times out:
*/
if (wait_reqd && settimeout) {
/* Check if this thread wants to wait forever: */
if (pthread->wakeup_time.tv_sec == -1) {
}
/* Check if this thread doesn't want to wait at all: */
else if (pthread->wakeup_time.tv_sec == 0 &&
pthread->wakeup_time.tv_nsec == 0) {
/* Override the caller's request to wait: */
wait_reqd = 0;
} else {
/*
* Calculate the time until this thread is
* ready, allowing for the clock resolution:
*/
ts1.tv_sec = pthread->wakeup_time.tv_sec - ts.tv_sec;
ts1.tv_nsec = pthread->wakeup_time.tv_nsec - ts.tv_nsec +
CLOCK_RES_NSEC;
/*
* Check for underflow of the nanosecond
* field:
*/
if (ts1.tv_nsec < 0) {
/*
* Allow for the underflow of the
* nanosecond field:
*/
ts1.tv_sec--;
ts1.tv_nsec += 1000000000;
}
/*
* Check for overflow of the nanosecond
* field:
*/
if (ts1.tv_nsec >= 1000000000) {
/*
* Allow for the overflow of the
* nanosecond field:
*/
ts1.tv_sec++;
ts1.tv_nsec -= 1000000000;
}
/*
* Convert the timespec structure to a
* timeval structure:
*/
TIMESPEC_TO_TIMEVAL(&tv1, &ts1);
/*
* Check if no time value has been found yet,
* or if the thread will be ready sooner that
* the earliest one found so far:
*/
if ((tv.tv_sec == 0 && tv.tv_usec == 0) || timercmp(&tv1, &tv, <)) {
/* Update the time value: */
tv.tv_sec = tv1.tv_sec;
tv.tv_usec = tv1.tv_usec;
}
}
}
}
/* Check if the caller wants to wait: */
if (wait_reqd) {
/* Check if no threads were found with timeouts: */
if (tv.tv_sec == 0 && tv.tv_usec == 0) {
/* Wait forever: */
p_tv = NULL;
} else {
/*
* Point to the time value structure which contains
* the earliest time that a thread will be ready:
*/
p_tv = &tv;
}
/*
* Flag the pthread kernel as in a select. This is to avoid
* the window between the next statement that unblocks
* signals and the select statement which follows.
*/
_thread_kern_in_select = 1;
/*
* Wait for a file descriptor to be ready for read, write, or
* an exception, or a timeout to occur:
*/
count = _thread_sys_select(nfds + 1, &fd_set_read, &fd_set_write, &fd_set_except, p_tv);
/* Reset the kernel in select flag: */
_thread_kern_in_select = 0;
/*
* Check if it is possible that there are bytes in the kernel
* read pipe waiting to be read:
*/
if (count < 0 || FD_ISSET(_thread_kern_pipe[0], &fd_set_read)) {
/*
* Check if the kernel read pipe was included in the
* count:
*/
if (count > 0) {
/*
* Remove the kernel read pipe from the
* count:
*/
FD_CLR(_thread_kern_pipe[0], &fd_set_read);
/* Decrement the count of file descriptors: */
count--;
}
/*
* Enter a loop to read (and trash) bytes from the
* pthread kernel pipe:
*/
while ((num = _thread_sys_read(_thread_kern_pipe[0], bufr, sizeof(bufr))) > 0) {
/*
* The buffer read contains one byte per
* signal and each byte is the signal number.
* This data is not used, but the fact that
* the signal handler wrote to the pipe *is*
* used to cause the _select call
* to complete if the signal occurred between
* the time when signals were unblocked and
* the _select select call being
* made.
*/
}
}
}
/* Check if there are file descriptors to poll: */
else if (count > 0) {
/*
* Point to the time value structure which has been zeroed so
* that the call to _select will not wait:
*/
p_tv = &tv;
/* Poll file descrptors without wait: */
count = _thread_sys_select(nfds + 1, &fd_set_read, &fd_set_write, &fd_set_except, p_tv);
}
/*
* Check if any file descriptors are ready:
*/
if (count > 0) {
/*
* Enter a loop to look for threads waiting on file
* descriptors that are flagged as available by the
* _select syscall:
*/
for (pthread = _thread_link_list; pthread != NULL; pthread = pthread->nxt) {
/* Process according to thread state: */
switch (pthread->state) {
/*
* States which do not depend on file
* descriptor I/O operations:
*/
case PS_RUNNING:
case PS_COND_WAIT:
case PS_DEAD:
case PS_FDLR_WAIT:
case PS_FDLW_WAIT:
case PS_FILE_WAIT:
case PS_JOIN:
case PS_MUTEX_WAIT:
case PS_SIGWAIT:
case PS_SLEEP_WAIT:
case PS_WAIT_WAIT:
case PS_SIGTHREAD:
case PS_STATE_MAX:
case PS_SUSPENDED:
/* Nothing to do here. */
break;
/* File descriptor read wait: */
case PS_FDR_WAIT:
/*
* Check if the file descriptor is available
* for read:
*/
if (FD_ISSET(pthread->data.fd.fd, &fd_set_read)) {
/*
* Change the thread state to allow
* it to read from the file when it
* is scheduled next:
*/
pthread->state = PS_RUNNING;
}
break;
/* File descriptor write wait: */
case PS_FDW_WAIT:
/*
* Check if the file descriptor is available
* for write:
*/
if (FD_ISSET(pthread->data.fd.fd, &fd_set_write)) {
/*
* Change the thread state to allow
* it to write to the file when it is
* scheduled next:
*/
pthread->state = PS_RUNNING;
}
break;
/* Select wait: */
case PS_SELECT_WAIT:
/*
* Reset the flag that indicates if a file
* descriptor is ready for some type of
* operation:
*/
count_dec = 0;
/*
* Enter a loop to search though the
* thread-specific select file descriptors
* for the first descriptor that is ready:
*/
for (i = 0; i < pthread->data.select_data->nfds && count_dec == 0; i++) {
/*
* Check if this file descriptor does
* not have an exception:
*/
if (FD_ISSET(i, &pthread->data.select_data->exceptfds) && FD_ISSET(i, &fd_set_except)) {
/*
* Flag this file descriptor
* as ready:
*/
count_dec = 1;
}
/*
* Check if this file descriptor is
* not ready for write:
*/
if (FD_ISSET(i, &pthread->data.select_data->writefds) && FD_ISSET(i, &fd_set_write)) {
/*
* Flag this file descriptor
* as ready:
*/
count_dec = 1;
}
/*
* Check if this file descriptor is
* not ready for read:
*/
if (FD_ISSET(i, &pthread->data.select_data->readfds) && FD_ISSET(i, &fd_set_read)) {
/*
* Flag this file descriptor
* as ready:
*/
count_dec = 1;
}
}
/*
* Check if any file descriptors are ready
* for the current thread:
*/
if (count_dec) {
/*
* Reset the count of file
* descriptors that are ready for
* this thread:
*/
found_one = 0;
/*
* Enter a loop to search though the
* thread-specific select file
* descriptors:
*/
for (i = 0; i < pthread->data.select_data->nfds; i++) {
/*
* Reset the count of
* operations for which the
* current file descriptor is
* ready:
*/
count_dec = 0;
/*
* Check if this file
* descriptor is selected for
* exceptions:
*/
if (FD_ISSET(i, &pthread->data.select_data->exceptfds)) {
/*
* Check if this file
* descriptor has an
* exception:
*/
if (FD_ISSET(i, &fd_set_except)) {
/*
* Increment
* the count
* for this
* file:
*/
count_dec++;
} else {
/*
* Clear the
* file
* descriptor
* in the
* thread-spec
* ific file
* descriptor
* set:
*/
FD_CLR(i, &pthread->data.select_data->exceptfds);
}
}
/*
* Check if this file
* descriptor is selected for
* write:
*/
if (FD_ISSET(i, &pthread->data.select_data->writefds)) {
/*
* Check if this file
* descriptor is
* ready for write:
*/
if (FD_ISSET(i, &fd_set_write)) {
/*
* Increment
* the count
* for this
* file:
*/
count_dec++;
} else {
/*
* Clear the
* file
* descriptor
* in the
* thread-spec
* ific file
* descriptor
* set:
*/
FD_CLR(i, &pthread->data.select_data->writefds);
}
}
/*
* Check if this file
* descriptor is selected for
* read:
*/
if (FD_ISSET(i, &pthread->data.select_data->readfds)) {
/*
* Check if this file
* descriptor is
* ready for read:
*/
if (FD_ISSET(i, &fd_set_read)) {
/*
* Increment
* the count
* for this
* file:
*/
count_dec++;
} else {
/*
* Clear the
* file
* descriptor
* in the
* thread-spec
* ific file
* descriptor
* set:
*/
FD_CLR(i, &pthread->data.select_data->readfds);
}
}
/*
* Check if the current file
* descriptor is ready for
* any one of the operations:
*/
if (count_dec > 0) {
/*
* Increment the
* count of file
* descriptors that
* are ready for the
* current thread:
*/
found_one++;
}
}
/*
* Return the number of file
* descriptors that are ready:
*/
pthread->data.select_data->nfds = found_one;
/*
* Change the state of the current
* thread to run:
*/
pthread->state = PS_RUNNING;
}
break;
}
}
}
/* Nothing to return. */
return;
}
void
_thread_kern_set_timeout(struct timespec * timeout)
{
struct timespec current_time;
struct timeval tv;
/* Reset the timeout flag for the running thread: */
_thread_run->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:
*/
_thread_run->wakeup_time.tv_sec = -1;
_thread_run->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': */
_thread_run->wakeup_time.tv_sec = 0;
_thread_run->wakeup_time.tv_nsec = 0;
} else {
/* Get the current time: */
gettimeofday(&tv, NULL);
TIMEVAL_TO_TIMESPEC(&tv, &current_time);
/* Calculate the time for the current thread to wake up: */
_thread_run->wakeup_time.tv_sec = current_time.tv_sec + timeout->tv_sec;
_thread_run->wakeup_time.tv_nsec = current_time.tv_nsec + timeout->tv_nsec;
/* Check if the nanosecond field needs to wrap: */
if (_thread_run->wakeup_time.tv_nsec >= 1000000000) {
/* Wrap the nanosecond field: */
_thread_run->wakeup_time.tv_sec += 1;
_thread_run->wakeup_time.tv_nsec -= 1000000000;
}
}
return;
}
#endif
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