X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=sched.c;h=13993b13be128e261e989cb3963cfc2e73a693b4;hp=5c1857151ffd3d2efd26c5780056a513e1ed1ad0;hb=57a04f35f4e97d5f63079620dab3493832a851af;hpb=5f375bf464d99c5d6ce4126f5e815da1839105c5 diff --git a/sched.c b/sched.c index 5c185715..13993b13 100644 --- a/sched.c +++ b/sched.c @@ -1,5 +1,5 @@ /* - * Copyright (C) 2006-2009 Andre Noll + * Copyright (C) 2006-2014 Andre Noll * * Licensed under the GPL v2. For licencing details see COPYING. */ @@ -7,9 +7,7 @@ /** \file sched.c Paraslash's scheduling functions. */ #include -#include /* readdir() */ #include -#include #include "para.h" #include "ipc.h" @@ -17,76 +15,113 @@ #include "list.h" #include "sched.h" #include "string.h" +#include "time.h" #include "error.h" -static struct list_head pre_select_list, post_select_list; -static int initialized; +/** + * The possible states of a task. + * + * In addition to the states listed here, a task may also enter zombie state. + * This happens when its ->post_select function returns negative, the ->status + * field is then set to this return value. Such tasks are not scheduled any + * more (i.e. ->pre_select() and ->post_select() are no longer called), but + * they stay on the scheduler task list until \ref task_reap() or + * \ref sched_shutdown() is called. + */ +enum task_status { + /** Task has been reaped and may be removed from the task list. */ + TS_DEAD, + /** Task is active. */ + TS_RUNNING, +}; + +struct task { + /** A copy of the task name supplied when the task was registered. */ + char *name; + /** Copied during task_register(). */ + struct task_info info; + /* TS_RUNNING, TS_DEAD, or zombie (negative value). */ + int status; + /** Position of the task in the task list of the scheduler. */ + struct list_head node; + /** If less than zero, the task was notified by another task. */ + int notification; +}; static struct timeval now_struct; struct timeval *now = &now_struct; -/** - * Remove a task from the scheduler. - * - * \param t The task to remove. - * - * If the pre_select pointer of \a t is not \p NULL, it is removed from - * the pre_select list of the scheduler. Same goes for \a post_select. - */ -static void unregister_task(struct task *t) +static inline bool timeout_is_zero(struct sched *s) { - if (!initialized) - return; - PARA_INFO_LOG("unregistering %s (%s)\n", t->status, - t->error <0? para_strerror(-t->error) : "shutdown"); - if (t->pre_select) - list_del(&t->pre_select_node); - if (t->post_select) - list_del(&t->post_select_node); - t->error = -E_TASK_UNREGISTERED; + struct timeval *tv = &s->select_timeout; + return tv->tv_sec == 0 && tv->tv_usec == 0; } - static void sched_preselect(struct sched *s) { struct task *t, *tmp; - list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) { - if (t->error >= 0 && t->pre_select) - t->pre_select(s, t); -// PARA_INFO_LOG("%s \n", t->status); - if (t->error >= 0) + + list_for_each_entry_safe(t, tmp, &s->task_list, node) { + if (t->status < 0) continue; - /* - * We have to check whether the list is empty because the call - * to ->pre_select() might have called sched_shutdown(). In - * this case t has been unregistered already, so we must not - * unregister it again. - */ - if (list_empty(&pre_select_list)) - return; - unregister_task(t); + if (t->notification != 0) + sched_min_delay(s); + if (t->info.pre_select) + t->info.pre_select(s, t); } } -static void sched_post_select(struct sched *s) +static void unlink_and_free_task(struct task *t) +{ + PARA_INFO_LOG("freeing task %s\n", t->name); + list_del(&t->node); + free(t->name); + free(t); +} + +//#define SCHED_DEBUG 1 +static inline void call_post_select(struct sched *s, struct task *t) +{ + int ret; + +#ifndef SCHED_DEBUG + ret = t->info.post_select(s, t); +#else + struct timeval t1, t2, diff; + unsigned long pst; + + clock_get_realtime(&t1); + ret = t->info.post_select(s, t); + clock_get_realtime(&t2); + tv_diff(&t1, &t2, &diff); + pst = tv2ms(&diff); + if (pst > 50) + PARA_WARNING_LOG("%s: post_select time: %lums\n", + t->name, pst); +#endif + t->status = ret < 0? ret : TS_RUNNING; +} + +static unsigned sched_post_select(struct sched *s) { struct task *t, *tmp; + unsigned num_running_tasks = 0; - list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) { - if (t->error >= 0) - t->post_select(s, t); -// PARA_INFO_LOG("%s: %d\n", t->status, t->ret); - if (t->error >= 0) - continue; - /* nec., see sched_preselect() */ - if (list_empty(&post_select_list)) - return; - unregister_task(t); + list_for_each_entry_safe(t, tmp, &s->task_list, node) { + if (t->status == TS_DEAD) /* task has been reaped */ + unlink_and_free_task(t); + else if (t->status == TS_RUNNING) { + call_post_select(s, t); /* sets t->status */ + t->notification = 0; + if (t->status == TS_RUNNING) + num_running_tasks++; + } } + return num_running_tasks; } /** - * The core function for all paraslash programs. + * The core function of all paraslash programs. * * \param s Pointer to the scheduler struct. * @@ -95,29 +130,27 @@ static void sched_post_select(struct sched *s) * the fd sets of \a s. Next, it calls para_select() and makes the result available * to the registered tasks by calling their post_select hook. * - * \return Zero if no more tasks are left in either of the two lists, negative - * if para_select returned an error. + * \return Zero if no more tasks are left in the task list, negative if the + * select function returned an error. * - * \sa task, now. + * \sa \ref task, \ref now. */ int schedule(struct sched *s) { int ret; + unsigned num_running_tasks; - if (!initialized) - return -E_NOT_INITIALIZED; if (!s->select_function) s->select_function = para_select; again: FD_ZERO(&s->rfds); FD_ZERO(&s->wfds); - s->timeout = s->default_timeout; + s->select_timeout = s->default_timeout; s->max_fileno = -1; - gettimeofday(now, NULL); + clock_get_realtime(now); sched_preselect(s); - if (list_empty(&pre_select_list) && list_empty(&post_select_list)) - return 0; - ret = s->select_function(s->max_fileno + 1, &s->rfds, &s->wfds, &s->timeout); + ret = s->select_function(s->max_fileno + 1, &s->rfds, &s->wfds, + &s->select_timeout); if (ret < 0) return ret; if (ret == 0) { @@ -130,149 +163,264 @@ again: FD_ZERO(&s->rfds); FD_ZERO(&s->wfds); } - gettimeofday(now, NULL); - sched_post_select(s); - if (list_empty(&pre_select_list) && list_empty(&post_select_list)) + clock_get_realtime(now); + num_running_tasks = sched_post_select(s); + if (num_running_tasks == 0) return 0; goto again; } /** - * Initialize the paraslash scheduler. + * Obtain the error status of a task and deallocate its resources. + * + * \param tptr Identifies the task to reap. + * + * This function is similar to wait(2) in that it returns information about a + * terminated task and allows to release the resources associated with the + * task. Until this function is called, the terminated task remains in a zombie + * state. + * + * \return If \a tptr is \p NULL, or \a *tptr is \p NULL, the function does + * nothing and returns zero. Otherwise, it is checked whether the task + * identified by \a tptr is still running. If it is, the function returns zero + * and again, no action is taken. Otherwise the (negative) error code of the + * terminated task is returned and \a *tptr is set to \p NULL. The task will + * then be removed removed from the scheduler task list. + * + * \sa \ref sched_shutdown(), wait(2). */ -static void init_sched(void) +int task_reap(struct task **tptr) { - PARA_INFO_LOG("initializing scheduler\n"); - INIT_LIST_HEAD(&pre_select_list); - INIT_LIST_HEAD(&post_select_list); - initialized = 1; + struct task *t; + int ret; + + if (!tptr) + return 0; + t = *tptr; + if (!t) + return 0; + if (t->status >= 0) + return 0; + ret = t->status; + /* + * With list_for_each_entry_safe() it is only safe to remove the + * _current_ list item. Since we are being called from the loop in + * schedule() via some task's ->post_select() function, freeing the + * given task here would result in use-after-free bugs in schedule(). + * So we only set the task status to TS_DEAD which tells schedule() to + * free the task in the next iteration of its loop. + */ + t->status = TS_DEAD; + + *tptr = NULL; + return ret; } /** - * Add a task to the scheduler. - * - * \param t the task to add + * Deallocate all resources of all tasks of a scheduler instance. * - * If the pre_select pointer of \a t is not \p NULL, it is added to - * the pre_select list of the scheduler. Same goes for post_select. + * \param s The scheduler instance. * - * \sa task::pre_select, task::post_select + * This should only be called after \ref schedule() has returned. */ -void register_task(struct task *t) +void sched_shutdown(struct sched *s) { - if (!initialized) - init_sched(); - PARA_INFO_LOG("registering %s (%p)\n", t->status, t); - if (t->pre_select) { - PARA_DEBUG_LOG("pre_select: %p\n", &t->pre_select); - list_add_tail(&t->pre_select_node, &pre_select_list); - } - if (t->post_select) { - PARA_DEBUG_LOG("post_select: %p\n", &t->post_select); - list_add_tail(&t->post_select_node, &post_select_list); + struct task *t, *tmp; + + list_for_each_entry_safe(t, tmp, &s->task_list, node) { + if (t->status == TS_RUNNING) + /* The task list should contain only terminated tasks. */ + PARA_WARNING_LOG("shutting down running task %s\n", + t->name); + unlink_and_free_task(t); } } /** - * Unregister all tasks. + * Add a task to the scheduler task list. + * + * \param info Task information supplied by the caller. + * \param s The scheduler instance. * - * This will cause \a schedule() to return immediately because both the - * \a pre_select_list and the \a post_select_list are empty. + * \return A pointer to a newly allocated task structure. It will be + * freed by sched_shutdown(). */ -void sched_shutdown(void) +struct task *task_register(struct task_info *info, struct sched *s) { - struct task *t, *tmp; + struct task *t = para_malloc(sizeof(*t)); - if (!initialized) - return; - list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) - unregister_task(t); - list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) - unregister_task(t); - initialized = 0; + assert(info->post_select); + + if (!s->task_list.next) + INIT_LIST_HEAD(&s->task_list); + + t->info = *info; + t->name = para_strdup(info->name); + t->notification = 0; + t->status = TS_RUNNING; + list_add_tail(&t->node, &s->task_list); + return t; +} + +/** + * Obtain the context pointer of a task. + * + * \param t Return this task's context pointer. + * + * \return A pointer to the memory location specified previously as \a + * task_info->context when the task was registered with \ref task_register(). + */ +void *task_context(struct task *t) +{ + return t->info.context; } /** * Get the list of all registered tasks. * + * \param s The scheduler instance to get the task list from. + * * \return The task list. * - * Each entry of the list contains an identifier which is simply a hex number - * that may be used in \a kill_task() to terminate the task. - * The result ist dynamically allocated and must be freed by the caller. + * Each entry of the list contains an identifier which is simply a hex number. + * The result is dynamically allocated and must be freed by the caller. */ -char *get_task_list(void) +char *get_task_list(struct sched *s) { struct task *t, *tmp; char *msg = NULL; - if (!initialized) - return NULL; - list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) { - char *tmp_msg; - tmp_msg = make_message("%s%p\tpre\t%s\n", msg? msg : "", t, t->status); - free(msg); - msg = tmp_msg; - } - list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) { + list_for_each_entry_safe(t, tmp, &s->task_list, node) { char *tmp_msg; -// if (t->pre_select) -// continue; - tmp_msg = make_message("%s%p\tpost\t%s\n", msg? msg : "", t, t->status); + tmp_msg = make_message("%s%p\t%s\t%s\n", msg? msg : "", t, + t->status == TS_DEAD? "dead" : + (t->status == TS_RUNNING? "running" : "zombie"), + t->name); free(msg); msg = tmp_msg; } - //PARA_DEBUG_LOG("task list:\n%s", msg); return msg; } /** - * Simulate an error for the given task. + * Set the notification value of a task. * - * \param id The task identifier. + * \param t The task to notify. + * \param err A positive error code. * - * Find the task identified by \a id, set the tasks' error value to - * \p -E_TASK_KILLED and unregister the task. + * Tasks which honor notifications are supposed to call \ref + * task_get_notification() in their post_select function and act on the + * returned notification value. * - * \return Positive on success, negative on errors (e.g. if \a id does not - * correspond to a registered task). + * If the scheduler detects during its pre_select loop that at least one task + * has been notified, the loop terminates, and the post_select methods of all + * taks are immediately called again. + * + * The notification for a task is reset after the call to its post_select + * method. + * + * \sa \ref task_get_notification(). */ -int kill_task(char *id) +void task_notify(struct task *t, int err) { - struct task *t, *tmp; - char buf[20]; + assert(err > 0); + if (t->notification == -err) /* ignore subsequent notifications */ + return; + PARA_INFO_LOG("notifying task %s: %s\n", t->name, para_strerror(err)); + t->notification = -err; +} - if (!initialized) - return -E_NOT_INITIALIZED; - list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) { - sprintf(buf, "%p", t); - if (strcmp(id, buf)) - continue; - t->error = -E_TASK_KILLED; - return 1; - } - list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) { - sprintf(buf, "%p", t); - if (strcmp(id, buf)) - continue; - t->error = -E_TASK_KILLED; +/** + * Return the notification value of a task. + * + * \param t The task to get the notification value from. + * + * \return The notification value. If this is negative, the task has been + * notified by another task. Tasks are supposed to check for notifications by + * calling this function from their post_select method. + * + * \sa \ref task_notify(). + */ +int task_get_notification(const struct task *t) +{ + return t->notification; +} + +/** + * Return the status value of a task. + * + * \param t The task to get the status value from. + * + * \return Zero if task does not exist, one if task is running, negative error + * code if task has terminated. + */ +int task_status(const struct task *t) +{ + if (!t) + return 0; + if (t->status == TS_DEAD) /* pretend dead tasks don't exist */ + return 0; + if (t->status == TS_RUNNING) return 1; - } - return -E_NO_SUCH_TASK; + return t->status; } +/** + * Set the notification value of all tasks of a scheduler instance. + * + * \param s The scheduler instance whose tasks should be notified. + * \param err A positive error code. + * + * This simply iterates over all existing tasks of \a s and sets each + * task's notification value to \p -err. + */ +void task_notify_all(struct sched *s, int err) +{ + struct task *t; + + list_for_each_entry(t, &s->task_list, node) + task_notify(t, err); +} + +/** + * Set the select timeout to the minimal possible value. + * + * \param s Pointer to the scheduler struct. + * + * This causes the next select() call to return immediately. + */ void sched_min_delay(struct sched *s) { - s->timeout.tv_sec = 0; - s->timeout.tv_usec = 1; + s->select_timeout.tv_sec = s->select_timeout.tv_usec = 0; } -void sched_request_timeout(struct timeval *timeout, struct sched *s) +/** + * Impose an upper bound for the timeout of the next select() call. + * + * \param to Maximal allowed timeout. + * \param s Pointer to the scheduler struct. + * + * If the current scheduler timeout is already smaller than \a to, this + * function does nothing. Otherwise the timeout for the next select() call is + * set to the given value. + * + * \sa sched_request_timeout_ms(). + */ +void sched_request_timeout(struct timeval *to, struct sched *s) { - if (tv_diff(&s->timeout, timeout, NULL) > 0) - s->timeout = *timeout; + if (tv_diff(&s->select_timeout, to, NULL) > 0) + s->select_timeout = *to; } +/** + * Force the next select() call to return before the given amount of milliseconds. + * + * \param ms The maximal allowed timeout in milliseconds. + * \param s Pointer to the scheduler struct. + * + * Like sched_request_timeout() this imposes an upper bound on the timeout + * value for the next select() call. + */ void sched_request_timeout_ms(long unsigned ms, struct sched *s) { struct timeval tv; @@ -280,13 +428,46 @@ void sched_request_timeout_ms(long unsigned ms, struct sched *s) sched_request_timeout(&tv, s); } -void sched_request_barrier(struct timeval *barrier, struct sched *s) +/** + * Force the next select() call to return before the given future time. + * + * \param barrier Absolute time before select() should return. + * \param s Pointer to the scheduler struct. + * + * \return If \a barrier is in the past, this function does nothing and returns + * zero. Otherwise it returns one. + * + * \sa sched_request_barrier_or_min_delay(). + */ +int sched_request_barrier(struct timeval *barrier, struct sched *s) { struct timeval diff; if (tv_diff(now, barrier, &diff) > 0) - return; + return 0; sched_request_timeout(&diff, s); + return 1; } +/** + * Force the next select() call to return before the given time. + * + * \param barrier Absolute time before select() should return. + * \param s Pointer to the scheduler struct. + * + * \return If \a barrier is in the past, this function requests a minimal + * timeout and returns zero. Otherwise it returns one. + * + * \sa sched_min_delay(), sched_request_barrier(). + */ +int sched_request_barrier_or_min_delay(struct timeval *barrier, struct sched *s) +{ + struct timeval diff; + if (tv_diff(now, barrier, &diff) > 0) { + sched_min_delay(s); + return 0; + } + sched_request_timeout(&diff, s); + return 1; +}