diff options
Diffstat (limited to 'linuxthreads/sysdeps/pthread/timer_routines.c')
| -rw-r--r-- | linuxthreads/sysdeps/pthread/timer_routines.c | 528 |
1 files changed, 528 insertions, 0 deletions
diff --git a/linuxthreads/sysdeps/pthread/timer_routines.c b/linuxthreads/sysdeps/pthread/timer_routines.c new file mode 100644 index 0000000000..eb14643c32 --- /dev/null +++ b/linuxthreads/sysdeps/pthread/timer_routines.c @@ -0,0 +1,528 @@ +/* Helper code for POSIX timer implementation on LinuxThreads. + Copyright (C) 2000 Free Software Foundation, Inc. + This file is part of the GNU C Library. + Contributed by Kaz Kylheku <kaz@ashi.footprints.net>. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Library General Public License as + published by the Free Software Foundation; either version 2 of the + License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Library General Public License for more details. + + You should have received a copy of the GNU Library General Public + License along with the GNU C Library; see the file COPYING.LIB. If not, + write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, + Boston, MA 02111-1307, USA. */ + +#include <assert.h> +#include <pthread.h> +#include <stddef.h> +#include <time.h> + +#include "posix-timer.h" + + +/* Number of threads used. */ +#define THREAD_MAXNODES 16 + +/* Array containing the descriptors for the used threads. */ +static struct thread_node thread_array[THREAD_MAXNODES]; + +/* Static array with the structures for all the timers. */ +struct timer_node __timer_array[TIMER_MAX]; + +/* Global lock to protect operation on the lists. */ +pthread_mutex_t __timer_mutex = PTHREAD_MUTEX_INITIALIZER; + +/* Variable to protext initialization. */ +pthread_once_t __timer_init_once_control = PTHREAD_ONCE_INIT; + +/* Nonzero if initialization of timer implementation failed. */ +int __timer_init_failed; + +/* Node for the thread used to deliver signals. */ +struct thread_node __timer_signal_thread; + +/* Lists to keep free and used timers and threads. */ +struct list_links timer_free_list; +struct list_links thread_free_list; +struct list_links thread_active_list; + + +/* List handling functions. */ +static inline void +list_init (struct list_links *list) +{ + list->next = list->prev = list; +} + +static inline void +list_append (struct list_links *list, struct list_links *newp) +{ + newp->prev = list->prev; + newp->next = list; + list->prev->next = newp; + list->prev = list; +} + +static inline void +list_insbefore (struct list_links *list, struct list_links *newp) +{ + list_append (list, newp); +} + +static inline struct list_links * +list_first (struct list_links *list) +{ + return list->next; +} + +static inline struct list_links * +list_null (struct list_links *list) +{ + return list; +} + +static inline struct list_links * +list_next (struct list_links *list) +{ + return list->next; +} + +static inline int +list_isempty (struct list_links *list) +{ + return list->next == list; +} + + +/* Functions build on top of the list functions. */ +static inline struct thread_node * +thread_links2ptr (struct list_links *list) +{ + return (struct thread_node *) ((char *) list + - offsetof (struct thread_node, links)); +} + +static inline struct timer_node * +timer_links2ptr (struct list_links *list) +{ + return (struct timer_node *) ((char *) list + - offsetof (struct timer_node, links)); +} + + +/* Initialize a newly allocated thread structure. */ +static void +thread_init (struct thread_node *thread, const pthread_attr_t *attr) +{ + if (attr != NULL) + thread->attr = *attr; + else + { + pthread_attr_init (&thread->attr); + pthread_attr_setdetachstate (&thread->attr, PTHREAD_CREATE_DETACHED); + } + + thread->exists = 0; + list_init (&thread->timer_queue); + pthread_cond_init (&thread->cond, 0); + thread->current_timer = 0; + thread->captured = pthread_self (); +} + + +/* Initialize the global lists, and acquire global resources. Error + reporting is done by storing a non-zero value to the global variable + timer_init_failed. */ +static void +init_module (void) +{ + int i; + + list_init (&timer_free_list); + list_init (&thread_free_list); + list_init (&thread_active_list); + + for (i = 0; i < TIMER_MAX; ++i) + { + list_append (&timer_free_list, &__timer_array[i].links); + __timer_array[i].inuse = 0; + } + + for (i = 0; i < THREAD_MAXNODES - 1; ++i) + list_append (&thread_free_list, &thread_array[i].links); + + thread_init (&__timer_signal_thread, 0); +} + + +/* This is a handler executed in a child process after a fork() + occurs. It reinitializes the module, resetting all of the data + structures to their initial state. The mutex is initialized in + case it was locked in the parent process. */ +static void +reinit_after_fork (void) +{ + init_module (); + pthread_mutex_init (&__timer_mutex, 0); +} + + +/* Called once form pthread_once in timer_init. This initializes the + module and ensures that reinit_after_fork will be executed in any + child process. */ +void +__timer_init_once (void) +{ + init_module (); + pthread_atfork (0, 0, reinit_after_fork); +} + + +/* Deinitialize a thread that is about to be deallocated. */ +static void +thread_deinit (struct thread_node *thread) +{ + assert (list_isempty (&thread->timer_queue)); + pthread_cond_destroy (&thread->cond); +} + + +/* Allocate a thread structure from the global free list. Global + mutex lock must be held by caller. */ +struct thread_node * +__timer_thread_alloc (const pthread_attr_t *desired_attr) +{ + struct list_links *node = list_first (&thread_free_list); + + if (node != list_null (&thread_free_list)) + { + struct thread_node *thread = thread_links2ptr (node); + list_unlink (node); + thread_init (thread, desired_attr); + return thread; + } + + return 0; +} + + +/* Return a thread structure to the global free list. Global lock + must be held by caller. */ +void +__timer_thread_dealloc (struct thread_node *thread) +{ + thread_deinit (thread); + list_append (&thread_free_list, &thread->links); +} + + +/* + * Each of our threads which terminates executes this cleanup handler. We never + * terminate threads ourselves; if a thread gets here it means that the evil + * application has killed it. If the thread has timers, these require + * servicing and so we must hire a replacement thread right away. + * We must also unblock another thread that may have been waiting for + * this thread to finish servicing a timer (see timer_delete()). + */ + +static void +thread_cleanup (void *val) +{ + if (val != NULL) + { + struct thread_node *thread = val; + + /* How did the signal thread get killed? */ + assert (thread != &__timer_signal_thread); + + pthread_mutex_lock (&__timer_mutex); + + thread->exists = 0; + + /* We are no longer processing a timer event. */ + thread->current_timer = 0; + + if (list_isempty (&thread->timer_queue)) + { + list_unlink (&thread->links); + __timer_thread_dealloc (thread); + } + else + (void) __timer_thread_start (thread); + + pthread_mutex_unlock (&__timer_mutex); + + /* Unblock potentially blocked timer_delete(). */ + pthread_cond_broadcast (&thread->cond); + } +} + + +/* Handle a timer which is supposed to go off now. */ +static void +thread_expire_timer (struct thread_node *self, struct timer_node *timer) +{ + self->current_timer = timer; + + pthread_mutex_unlock (&__timer_mutex); + + switch (timer->event.sigev_notify) + { + case SIGEV_NONE: + assert (! "timer_create should never have created such a timer"); + break; + + case SIGEV_SIGNAL: + if (pthread_kill (self->captured, timer->event.sigev_signo) != 0) + { + if (pthread_kill (self->id, timer->event.sigev_signo) != 0) + abort (); + } + break; + + case SIGEV_THREAD: + timer->event.sigev_notify_function (timer->event.sigev_value); + break; + + default: + assert (! "unknown event"); + break; + } + + pthread_mutex_lock (&__timer_mutex); + + self->current_timer = 0; + + pthread_cond_broadcast (&self->cond); +} + + +/* Thread function; executed by each timer thread. The job of this + function is to wait on the thread's timer queue and expire the + timers in chronological order as close to their scheduled time as + possible. */ +static void * +thread_func (void *arg) +{ + struct thread_node *self = arg; + + /* Register cleanup handler, in case rogue application terminates + this thread. (This cannot happen to __timer_signal_thread, which + doesn't invoke application callbacks). */ + + pthread_cleanup_push (thread_cleanup, self); + + pthread_mutex_lock (&__timer_mutex); + + while (1) + { + struct list_links *first; + struct timer_node *timer = NULL; + + /* While the timer queue is not empty, inspect the first node. */ + first = list_first (&self->timer_queue); + if (first != list_null (&self->timer_queue)) + { + struct timespec now; + + timer = timer_links2ptr (first); + + /* This assumes that the elements of the list of one thread + are all for the same clock. */ + clock_gettime (timer->clock, &now); + + while (1) + { + /* If the timer is due or overdue, remove it from the queue. + If it's a periodic timer, re-compute its new time and + requeue it. Either way, perform the timer expiry. */ + if (timespec_compare (&now, &timer->expirytime) < 0) + break; + + list_unlink (first); + + if (timer->value.it_interval.tv_sec + || timer->value.it_interval.tv_nsec) + { + timespec_add (&timer->expirytime, &now, + &timer->value.it_interval); + (void) __timer_thread_queue_timer (self, timer); + } + + thread_expire_timer (self, timer); + + first = list_first (&self->timer_queue); + if (first == list_null (&self->timer_queue)) + break; + + timer = timer_links2ptr (first); + } + } + + /* If the queue is not empty, wait until the expiry time of the + first node. Otherwise wait indefinitely. Insertions at the + head of the queue must wake up the thread by broadcasting + this condition variable. */ + if (timer != NULL) + pthread_cond_timedwait (&self->cond, &__timer_mutex, + &timer->expirytime); + else + pthread_cond_wait (&self->cond, &__timer_mutex); + } + + pthread_mutex_unlock (&__timer_mutex); + pthread_cleanup_pop (1); + + return NULL; +} + + +/* Enqueue a timer in wakeup order in the thread's timer queue. */ +int +__timer_thread_queue_timer (struct thread_node *thread, + struct timer_node *insert) +{ + struct list_links *iter; + struct timer_node *matching = NULL; + struct timer_node *timer = NULL; + + for (iter = list_first (&thread->timer_queue); + iter != list_null (&thread->timer_queue); + iter = list_next (iter)) + { + timer = timer_links2ptr (iter); + + if (insert->clock == timer->clock) + { + matching = timer; + if (timespec_compare (&insert->expirytime, &timer->expirytime) < 0) + break; + } + } + + if (insert->clock != timer->clock) + { + if (matching == NULL) + /* We cannot queue this timer. */ + return -1; + + timer = matching; + } + + list_insbefore (iter, &insert->links); + + return 0; +} + + +/* Start a thread and associate it with the given thread node. Global + lock must be held by caller. */ +int +__timer_thread_start (struct thread_node *thread) +{ + int retval = 1; + + assert (!thread->exists); + + thread->exists = 1; + + if (pthread_create (&thread->id, &thread->attr, thread_func, thread) != 0) + { + thread->exists = 0; + retval = -1; + } + + return retval; +} + + +void +__timer_thread_wakeup (struct thread_node *thread) +{ + pthread_cond_broadcast (&thread->cond); +} + + +/* Compare two pthread_attr_t thread attributes for exact equality. + Returns 1 if they are equal, otherwise zero if they are not equal or + contain illegal values. This version is LinuxThreads-specific for + performance reason. One could use the access functions to get the + values of all the fields of the attribute structure. */ +static int +thread_attr_compare (const pthread_attr_t *left, const pthread_attr_t *right) +{ + return (left->__detachstate == right->__detachstate + && left->__schedpolicy == right->__schedpolicy + && (left->__schedparam.sched_priority + == right->__schedparam.sched_priority) + && left->__inheritsched == right->__inheritsched + && left->__scope == right->__scope); +} + + +/* Search the list of active threads and find one which has matching + attributes. Global mutex lock must be held by caller. */ +struct thread_node * +__timer_thread_find_matching (const pthread_attr_t *desired_attr) +{ + struct list_links *iter = list_first (&thread_active_list); + + while (iter != list_null (&thread_active_list)) + { + struct thread_node *candidate = thread_links2ptr (iter); + + if (thread_attr_compare (desired_attr, &candidate->attr)) + { + list_unlink (iter); + return candidate; + } + + iter = list_next (iter); + } + + return NULL; +} + + +/* Grab a free timer structure from the global free list. The global + lock must be held by the caller. */ +struct timer_node * +__timer_alloc (void) +{ + struct list_links *node = list_first (&timer_free_list); + + if (node != list_null (&timer_free_list)) + { + struct timer_node *timer = timer_links2ptr (node); + list_unlink (node); + timer->inuse = 1; + return timer; + } + + return NULL; +} + + +/* Return a timer structure to the global free list. The global lock + must be held by the caller. */ +void +__timer_dealloc (struct timer_node *timer) +{ + timer->thread = NULL; /* Break association between timer and thread. */ + timer->inuse = 0; + list_append (&timer_free_list, &timer->links); +} + + +/* Thread cancellation handler which unlocks a mutex. */ +void +__timer_mutex_cancel_handler (void *arg) +{ + pthread_mutex_unlock (arg); +} |