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fc8f3f5bfe
freebsd-dev/lib/libpthread/thread/thr_kern.c
Daniel Eischen fc8f3f5bfe Fix problems with cancellation while in critical regions. 
o Cancellation flags were not getting properly set/cleared.
  o Loops waiting for internal locks were not being exited
    correctly by a cancelled thread.
  o Minor spelling (cancelation -> cancellation) and formatting
    corrections (missing tab).

Found by:	tg
Reviewed by:	jasone
1999-12-17 00:57:54 +00:00

1136 lines
29 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 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 <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_poll(int wait_reqd);
static void
dequeue_signals(void);
static inline void
thread_run_switch_hook(pthread_t thread_out, pthread_t thread_in);
void
_thread_kern_sched(ucontext_t * scp)
{
#ifndef __alpha__
char *fdata;
#endif
pthread_t pthread, pthread_h = NULL;
struct itimerval itimer;
struct timespec ts, ts1;
struct timeval tv, tv1;
int set_timer = 0;
/*
* 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;
if (((_thread_run->cancelflags & PTHREAD_AT_CANCEL_POINT) == 0) &&
((_thread_run->cancelflags & PTHREAD_CANCEL_ASYNCHRONOUS) != 0)) {
/*
* Cancellations override signals.
*
* 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, _thread_run);
}
return;
} else
/* Flag the jump buffer was the last state saved: */
_thread_run->sig_saved = 0;
/* If the currently running thread is a user thread, save it: */
if ((_thread_run->flags & PTHREAD_FLAGS_PRIVATE) == 0)
_last_user_thread = _thread_run;
/*
* 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 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 (!(TAILQ_EMPTY(&_thread_list))) {
/* Get the current time of day: */
gettimeofday(&tv, NULL);
TIMEVAL_TO_TIMESPEC(&tv, &ts);
/*
* Protect the scheduling queues from access by the signal
* handler.
*/
_queue_signals = 1;
if (_thread_run != &_thread_kern_thread) {
/*
* This thread no longer needs to yield the CPU.
*/
_thread_run->yield_on_sig_undefer = 0;
/*
* 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;
/*
* Place the currently running thread into the
* appropriate queue(s).
*/
switch (_thread_run->state) {
case PS_DEAD:
case PS_STATE_MAX: /* to silence -Wall */
/*
* Dead 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).
*/
if ((_thread_run->slice_usec != -1) &&
(_thread_run->attr.sched_policy != SCHED_FIFO)) {
/*
* Accumulate the number of microseconds that
* this thread has run for:
*/
_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 for time quantum exceeded: */
if (_thread_run->slice_usec > TIMESLICE_USEC)
_thread_run->slice_usec = -1;
}
break;
/*
* States which do not depend on file descriptor I/O
* operations or timeouts:
*/
case PS_DEADLOCK:
case PS_FDLR_WAIT:
case PS_FDLW_WAIT:
case PS_FILE_WAIT:
case PS_JOIN:
case PS_MUTEX_WAIT:
case PS_SIGSUSPEND:
case PS_SIGTHREAD:
case PS_SIGWAIT:
case PS_SUSPENDED:
case PS_WAIT_WAIT:
/* No timeouts for these states: */
_thread_run->wakeup_time.tv_sec = -1;
_thread_run->wakeup_time.tv_nsec = -1;
/* Restart the time slice: */
_thread_run->slice_usec = -1;
/* Insert into the waiting queue: */
PTHREAD_WAITQ_INSERT(_thread_run);
break;
/* States which can timeout: */
case PS_COND_WAIT:
case PS_SLEEP_WAIT:
/* Restart the time slice: */
_thread_run->slice_usec = -1;
/* Insert into the waiting queue: */
PTHREAD_WAITQ_INSERT(_thread_run);
break;
/* States that require periodic work: */
case PS_SPINBLOCK:
/* No timeouts for this state: */
_thread_run->wakeup_time.tv_sec = -1;
_thread_run->wakeup_time.tv_nsec = -1;
/* Increment spinblock count: */
_spinblock_count++;
/* fall through */
case PS_FDR_WAIT:
case PS_FDW_WAIT:
case PS_POLL_WAIT:
case PS_SELECT_WAIT:
/* Restart the time slice: */
_thread_run->slice_usec = -1;
/* Insert into the waiting queue: */
PTHREAD_WAITQ_INSERT(_thread_run);
/* Insert into the work queue: */
PTHREAD_WORKQ_INSERT(_thread_run);
break;
}
}
/* Unprotect the scheduling queues: */
_queue_signals = 0;
/*
* Poll file descriptors to update the state of threads
* waiting on file I/O where data may be available:
*/
_thread_kern_poll(0);
/* Protect the scheduling queues: */
_queue_signals = 1;
/*
* 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)))) {
switch (pthread->state) {
case PS_POLL_WAIT:
case PS_SELECT_WAIT:
/* Return zero file descriptors ready: */
pthread->data.poll_data->nfds = 0;
/* fall through */
default:
/*
* 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();
break;
}
/*
* Flag the timeout in the thread structure:
*/
pthread->timeout = 1;
}
PTHREAD_WAITQ_CLEARACTIVE();
/*
* Check if there is a current runnable thread that isn't
* already in the ready queue:
*/
if ((_thread_run != &_thread_kern_thread) &&
(_thread_run->state == PS_RUNNING) &&
((_thread_run->flags & PTHREAD_FLAGS_IN_PRIOQ) == 0)) {
if (_thread_run->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(_thread_run);
} else {
/*
* The thread hasn't exceeded its
* interval. Place it at the head
* of the queue for its priority.
*/
PTHREAD_PRIOQ_INSERT_HEAD(_thread_run);
}
}
/*
* 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:
*/
_thread_run = &_thread_kern_thread;
/* Unprotect the scheduling queues: */
_queue_signals = 0;
/*
* There are no threads ready to run, so wait until
* something happens that changes this condition:
*/
_thread_kern_poll(1);
}
else {
/* Remove the thread from the ready queue: */
PTHREAD_PRIOQ_REMOVE(pthread_h);
/* Get first thread on the waiting list: */
pthread = TAILQ_FIRST(&_waitingq);
/* Check to see if there is more than one thread: */
if (pthread_h != TAILQ_FIRST(&_thread_list) ||
TAILQ_NEXT(pthread_h, tle) != NULL)
set_timer = 1;
else
set_timer = 0;
/* Unprotect the scheduling queues: */
_queue_signals = 0;
/*
* Check for signals queued while the scheduling
* queues were protected:
*/
while (_sigq_check_reqd != 0) {
/* Clear before handling queued signals: */
_sigq_check_reqd = 0;
/* Protect the scheduling queues again: */
_queue_signals = 1;
dequeue_signals();
/*
* Check for a higher priority thread that
* became runnable due to signal handling.
*/
if (((pthread = PTHREAD_PRIOQ_FIRST()) != NULL) &&
(pthread->active_priority > pthread_h->active_priority)) {
/*
* Insert the lower priority thread
* at the head of its priority list:
*/
PTHREAD_PRIOQ_INSERT_HEAD(pthread_h);
/* Remove the thread from the ready queue: */
PTHREAD_PRIOQ_REMOVE(pthread);
/* There's a new thread in town: */
pthread_h = pthread;
}
/* Get first thread on the waiting list: */
pthread = TAILQ_FIRST(&_waitingq);
/*
* Check to see if there is more than one
* thread:
*/
if (pthread_h != TAILQ_FIRST(&_thread_list) ||
TAILQ_NEXT(pthread_h, tle) != NULL)
set_timer = 1;
else
set_timer = 0;
/* Unprotect the scheduling queues: */
_queue_signals = 0;
}
/* Make the selected thread the current thread: */
_thread_run = pthread_h;
/*
* 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;
/*
* Define the maximum time before a scheduling signal
* 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;
/* Get first thread on the waiting list: */
if ((pthread != NULL) &&
(pthread->wakeup_time.tv_sec != -1)) {
/*
* 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:
*/
while (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:
*/
while (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 the thread will be ready
* sooner than the earliest ones found
* so far:
*/
if (timercmp(&tv1, &itimer.it_value, <)) {
/*
* Update the time value:
*/
itimer.it_value.tv_sec = tv1.tv_sec;
itimer.it_value.tv_usec = tv1.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;
}
/* Check if there is more than one thread: */
if (set_timer != 0) {
/*
* Start the interval timer for the
* calculated time interval:
*/
if (setitimer(_ITIMER_SCHED_TIMER, &itimer, NULL) != 0) {
/*
* Cannot initialise the timer, so
* abort this process:
*/
PANIC("Cannot set scheduling 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;
/*
* If we had a context switch, run any
* installed switch hooks.
*/
if ((_sched_switch_hook != NULL) &&
(_last_user_thread != _thread_run)) {
thread_run_switch_hook(_last_user_thread,
_thread_run);
}
_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)
{
/*
* 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;
/*
* Prevent the signal handler from fiddling with this thread
* before its state is set and is placed into the proper queue.
*/
_queue_signals = 1;
/* 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;
}
void
_thread_kern_sched_state_unlock(enum pthread_state state,
spinlock_t *lock, char *fname, int lineno)
{
/*
* 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;
/*
* Prevent the signal handler from fiddling with this thread
* before its state is set and it is placed into the proper
* queue(s).
*/
_queue_signals = 1;
/* Change the state of the current thread: */
_thread_run->state = state;
_thread_run->fname = fname;
_thread_run->lineno = lineno;
_SPINUNLOCK(lock);
/* Schedule the next thread that is ready: */
_thread_kern_sched(NULL);
return;
}
static void
_thread_kern_poll(int wait_reqd)
{
int count = 0;
int i, found;
int kern_pipe_added = 0;
int nfds = 0;
int timeout_ms = 0;
struct pthread *pthread;
struct timespec ts;
struct timeval tv;
/* Check if the caller wants to wait: */
if (wait_reqd == 0) {
timeout_ms = 0;
}
else {
/* Get the current time of day: */
gettimeofday(&tv, NULL);
TIMEVAL_TO_TIMESPEC(&tv, &ts);
_queue_signals = 1;
pthread = TAILQ_FIRST(&_waitingq);
_queue_signals = 0;
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.
*/
timeout_ms = INFTIM;
}
else {
/*
* Calculate the time left for the next thread to
* timeout allowing for the clock resolution:
*/
timeout_ms = ((pthread->wakeup_time.tv_sec - ts.tv_sec) *
1000) + ((pthread->wakeup_time.tv_nsec - ts.tv_nsec +
_clock_res_nsec) / 1000000);
/*
* Don't allow negative timeouts:
*/
if (timeout_ms < 0)
timeout_ms = 0;
}
}
/* Protect the scheduling queues: */
_queue_signals = 1;
/*
* Check to see if the signal queue needs to be walked to look
* for threads awoken by a signal while in the scheduler.
*/
if (_sigq_check_reqd != 0) {
/* Reset flag before handling queued signals: */
_sigq_check_reqd = 0;
dequeue_signals();
}
/*
* 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;
}
/*
* Form the poll table:
*/
nfds = 0;
if (timeout_ms != 0) {
/* Add the kernel pipe to the poll table: */
_thread_pfd_table[nfds].fd = _thread_kern_pipe[0];
_thread_pfd_table[nfds].events = POLLRDNORM;
_thread_pfd_table[nfds].revents = 0;
nfds++;
kern_pipe_added = 1;
}
PTHREAD_WAITQ_SETACTIVE();
TAILQ_FOREACH(pthread, &_workq, qe) {
switch (pthread->state) {
case 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--;
/*
* Since there is at least one runnable
* thread, disable the wait.
*/
timeout_ms = 0;
}
break;
/* File descriptor read wait: */
case PS_FDR_WAIT:
/* Limit number of polled files to table size: */
if (nfds < _thread_dtablesize) {
_thread_pfd_table[nfds].events = POLLRDNORM;
_thread_pfd_table[nfds].fd = pthread->data.fd.fd;
nfds++;
}
break;
/* File descriptor write wait: */
case PS_FDW_WAIT:
/* Limit number of polled files to table size: */
if (nfds < _thread_dtablesize) {
_thread_pfd_table[nfds].events = POLLWRNORM;
_thread_pfd_table[nfds].fd = pthread->data.fd.fd;
nfds++;
}
break;
/* File descriptor poll or select wait: */
case PS_POLL_WAIT:
case PS_SELECT_WAIT:
/* Limit number of polled files to table size: */
if (pthread->data.poll_data->nfds + nfds <
_thread_dtablesize) {
for (i = 0; i < pthread->data.poll_data->nfds; i++) {
_thread_pfd_table[nfds + i].fd =
pthread->data.poll_data->fds[i].fd;
_thread_pfd_table[nfds + i].events =
pthread->data.poll_data->fds[i].events;
}
nfds += pthread->data.poll_data->nfds;
}
break;
/* Other states do not depend on file I/O. */
default:
break;
}
}
PTHREAD_WAITQ_CLEARACTIVE();
/*
* Wait for a file descriptor to be ready for read, write, or
* an exception, or a timeout to occur:
*/
count = _thread_sys_poll(_thread_pfd_table, nfds, timeout_ms);
if (kern_pipe_added != 0)
/*
* Remove the pthread kernel pipe file descriptor
* from the pollfd table:
*/
nfds = 1;
else
nfds = 0;
/*
* Check if it is possible that there are bytes in the kernel
* read pipe waiting to be read:
*/
if (count < 0 || ((kern_pipe_added != 0) &&
(_thread_pfd_table[0].revents & POLLRDNORM))) {
/*
* If the kernel read pipe was included in the
* count:
*/
if (count > 0) {
/* Decrement the count of file descriptors: */
count--;
}
if (_sigq_check_reqd != 0) {
/* Reset flag before handling signals: */
_sigq_check_reqd = 0;
dequeue_signals();
}
}
/*
* 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
* _poll syscall:
*/
PTHREAD_WAITQ_SETACTIVE();
TAILQ_FOREACH(pthread, &_workq, qe) {
switch (pthread->state) {
case 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--;
}
break;
/* File descriptor read wait: */
case PS_FDR_WAIT:
if ((nfds < _thread_dtablesize) &&
(_thread_pfd_table[nfds].revents & POLLRDNORM)) {
PTHREAD_WAITQ_CLEARACTIVE();
PTHREAD_WORKQ_REMOVE(pthread);
PTHREAD_NEW_STATE(pthread,PS_RUNNING);
PTHREAD_WAITQ_SETACTIVE();
}
nfds++;
break;
/* File descriptor write wait: */
case PS_FDW_WAIT:
if ((nfds < _thread_dtablesize) &&
(_thread_pfd_table[nfds].revents & POLLWRNORM)) {
PTHREAD_WAITQ_CLEARACTIVE();
PTHREAD_WORKQ_REMOVE(pthread);
PTHREAD_NEW_STATE(pthread,PS_RUNNING);
PTHREAD_WAITQ_SETACTIVE();
}
nfds++;
break;
/* File descriptor poll or select wait: */
case PS_POLL_WAIT:
case PS_SELECT_WAIT:
if (pthread->data.poll_data->nfds + nfds <
_thread_dtablesize) {
/*
* Enter a loop looking for I/O
* readiness:
*/
found = 0;
for (i = 0; i < pthread->data.poll_data->nfds; i++) {
if (_thread_pfd_table[nfds + i].revents != 0) {
pthread->data.poll_data->fds[i].revents =
_thread_pfd_table[nfds + i].revents;
found++;
}
}
/* Increment before destroying: */
nfds += pthread->data.poll_data->nfds;
if (found != 0) {
pthread->data.poll_data->nfds = found;
PTHREAD_WAITQ_CLEARACTIVE();
PTHREAD_WORKQ_REMOVE(pthread);
PTHREAD_NEW_STATE(pthread,PS_RUNNING);
PTHREAD_WAITQ_SETACTIVE();
}
}
else
nfds += pthread->data.poll_data->nfds;
break;
/* Other states do not depend on file I/O. */
default:
break;
}
}
PTHREAD_WAITQ_CLEARACTIVE();
}
else 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();
}
/* Unprotect the scheduling queues: */
_queue_signals = 0;
while (_sigq_check_reqd != 0) {
/* Handle queued signals: */
_sigq_check_reqd = 0;
/* Protect the scheduling queues: */
_queue_signals = 1;
dequeue_signals();
/* Unprotect the scheduling queues: */
_queue_signals = 0;
}
/* 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;
}
void
_thread_kern_sig_defer(void)
{
/* Allow signal deferral to be recursive. */
_thread_run->sig_defer_count++;
}
void
_thread_kern_sig_undefer(void)
{
pthread_t pthread;
int need_resched = 0;
/*
* Perform checks to yield only if we are about to undefer
* signals.
*/
if (_thread_run->sig_defer_count > 1) {
/* Decrement the signal deferral count. */
_thread_run->sig_defer_count--;
}
else if (_thread_run->sig_defer_count == 1) {
/* Reenable signals: */
_thread_run->sig_defer_count = 0;
/*
* Check if there are queued signals:
*/
while (_sigq_check_reqd != 0) {
/* Defer scheduling while we process queued signals: */
_thread_run->sig_defer_count = 1;
/* Clear the flag before checking the signal queue: */
_sigq_check_reqd = 0;
/* Dequeue and handle signals: */
dequeue_signals();
/*
* Avoiding an unnecessary check to reschedule, check
* to see if signal handling caused a higher priority
* thread to become ready.
*/
if ((need_resched == 0) &&
(((pthread = PTHREAD_PRIOQ_FIRST()) != NULL) &&
(pthread->active_priority > _thread_run->active_priority))) {
need_resched = 1;
}
/* Reenable signals: */
_thread_run->sig_defer_count = 0;
}
/* Yield the CPU if necessary: */
if (need_resched || _thread_run->yield_on_sig_undefer != 0) {
_thread_run->yield_on_sig_undefer = 0;
_thread_kern_sched(NULL);
}
}
}
static void
dequeue_signals(void)
{
char bufr[128];
int i, num;
pthread_t pthread;
/*
* Enter a loop to read and handle queued signals from the
* pthread kernel pipe:
*/
while (((num = _thread_sys_read(_thread_kern_pipe[0], bufr,
sizeof(bufr))) > 0) || (num == -1 && errno == EINTR)) {
/*
* The buffer read contains one byte per signal and
* each byte is the signal number.
*/
for (i = 0; i < num; i++) {
if ((int) bufr[i] == _SCHED_SIGNAL) {
/*
* Scheduling signals shouldn't ever be
* queued; just ignore it for now.
*/
}
else {
/* Handle this signal: */
pthread = _thread_sig_handle((int) bufr[i],
NULL);
if (pthread != NULL)
_thread_sig_deliver(pthread,
(int) bufr[i]);
}
}
}
if ((num < 0) && (errno != EAGAIN)) {
/*
* The only error we should expect is if there is
* no data to read.
*/
PANIC("Unable to read from thread kernel pipe");
}
}
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);
}
}
#endif
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