X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=sched.c;h=1db9169b38b511918cc711fc28dcb667e1242e5f;hp=8b68667bf453c481df6950ec727be3b134037f99;hb=5ff39998bf0ce71bd8fc8d0f002ceb81b711992f;hpb=42ddd68159d7eff0f3e7c225665c97f9abd59425 diff --git a/sched.c b/sched.c index 8b68667b..1db9169b 100644 --- a/sched.c +++ b/sched.c @@ -1,5 +1,5 @@ /* - * Copyright (C) 2006-2014 Andre Noll + * Copyright (C) 2006 Andre Noll * * Licensed under the GPL v2. For licencing details see COPYING. */ @@ -7,7 +7,6 @@ /** \file sched.c Paraslash's scheduling functions. */ #include -#include #include "para.h" #include "ipc.h" @@ -18,83 +17,104 @@ #include "time.h" #include "error.h" -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. +/** + * 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. */ -static void unregister_task(struct task *t) -{ - assert(t->error < 0); - PARA_INFO_LOG("unregistering %s (%s)\n", t->status, - para_strerror(-t->error)); - if (t->pre_select) - list_del(&t->pre_select_node); - if (t->post_select) - list_del(&t->post_select_node); -} +enum task_status { + /** Task has been reaped and may be removed from the task list. */ + TS_DEAD, + /** Task is active. */ + TS_RUNNING, +}; -static inline bool timeout_is_zero(struct sched *s) -{ - struct timeval *tv = &s->select_timeout; - return tv->tv_sec == 0 && tv->tv_usec == 0; -} +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; +const struct timeval *now = &now_struct; static void sched_preselect(struct sched *s) { struct task *t, *tmp; - list_for_each_entry_safe(t, tmp, &s->pre_select_list, pre_select_node) { + list_for_each_entry_safe(t, tmp, &s->task_list, node) { + if (t->status < 0) + continue; if (t->notification != 0) sched_min_delay(s); - if (t->pre_select) - t->pre_select(s, t); + if (t->info.pre_select) + t->info.pre_select(s, t->info.context); } } +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 - t->error = t->post_select(s, t); + ret = t->info.post_select(s, t->info.context); #else struct timeval t1, t2, diff; unsigned long pst; clock_get_realtime(&t1); - t->error = t->post_select(s, t); + ret = t->info.post_select(s, t->info.context); 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->status, pst); + t->name, pst); #endif + t->status = ret < 0? ret : TS_RUNNING; } -static void sched_post_select(struct sched *s) +static unsigned sched_post_select(struct sched *s) { struct task *t, *tmp; + unsigned num_running_tasks = 0; - list_for_each_entry_safe(t, tmp, &s->post_select_list, post_select_node) { - if (t->error >= 0) - call_post_select(s, t); -// PARA_INFO_LOG("%s: %d\n", t->status, t->ret); - t->notification = 0; - if (t->error >= 0) - continue; - 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. * @@ -103,14 +123,15 @@ 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 now. */ int schedule(struct sched *s) { int ret; + unsigned num_running_tasks; if (!s->select_function) s->select_function = para_select; @@ -119,7 +140,7 @@ again: FD_ZERO(&s->wfds); s->select_timeout = s->default_timeout; s->max_fileno = -1; - clock_get_realtime(now); + clock_get_realtime(&now_struct); sched_preselect(s); ret = s->select_function(s->max_fileno + 1, &s->rfds, &s->wfds, &s->select_timeout); @@ -135,42 +156,105 @@ again: FD_ZERO(&s->rfds); FD_ZERO(&s->wfds); } - clock_get_realtime(now); - sched_post_select(s); - if (list_empty(&s->pre_select_list) && list_empty(&s->post_select_list)) + clock_get_realtime(&now_struct); + num_running_tasks = sched_post_select(s); + if (num_running_tasks == 0) return 0; goto again; } /** - * Add a task to the scheduler. + * Obtain the error status of a task and deallocate its resources. + * + * \param tptr Identifies the task to reap. * - * \param t The task to add. - * \param s The scheduler instance to add the task to. + * 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. * - * 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. + * \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 task::pre_select, task::post_select + * \sa \ref sched_shutdown(), wait(2). */ -void register_task(struct sched *s, struct task *t) +int task_reap(struct task **tptr) { - PARA_INFO_LOG("registering %s (%p)\n", t->status, t); - t->notification = 0; - if (!s->pre_select_list.next) - INIT_LIST_HEAD(&s->pre_select_list); - if (!s->post_select_list.next) - INIT_LIST_HEAD(&s->post_select_list); - if (t->pre_select) { - PARA_DEBUG_LOG("pre_select: %p\n", &t->pre_select); - list_add_tail(&t->pre_select_node, &s->pre_select_list); - } - if (t->post_select) { - PARA_DEBUG_LOG("post_select: %p\n", &t->post_select); - list_add_tail(&t->post_select_node, &s->post_select_list); + 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; +} + +/** + * Deallocate all resources of all tasks of a scheduler instance. + * + * \param s The scheduler instance. + * + * This should only be called after \ref schedule() has returned. + */ +void sched_shutdown(struct sched *s) +{ + 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); } } +/** + * Add a task to the scheduler task list. + * + * \param info Task information supplied by the caller. + * \param s The scheduler instance. + * + * \return A pointer to a newly allocated task structure. It will be + * freed by sched_shutdown(). + */ +struct task *task_register(struct task_info *info, struct sched *s) +{ + struct task *t = para_malloc(sizeof(*t)); + + 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; +} + /** * Get the list of all registered tasks. * @@ -186,21 +270,15 @@ char *get_task_list(struct sched *s) struct task *t, *tmp; char *msg = NULL; - list_for_each_entry_safe(t, tmp, &s->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, &s->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; } @@ -228,7 +306,7 @@ void task_notify(struct task *t, int err) assert(err > 0); if (t->notification == -err) /* ignore subsequent notifications */ return; - PARA_INFO_LOG("notifying task %s: %s\n", t->status, para_strerror(err)); + PARA_INFO_LOG("notifying task %s: %s\n", t->name, para_strerror(err)); t->notification = -err; } @@ -243,11 +321,30 @@ void task_notify(struct task *t, int err) * * \sa \ref task_notify(). */ -int task_get_notification(struct task *t) +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 t->status; +} + /** * Set the notification value of all tasks of a scheduler instance. * @@ -261,9 +358,7 @@ void task_notify_all(struct sched *s, int err) { struct task *t; - list_for_each_entry(t, &s->pre_select_list, pre_select_node) - task_notify(t, err); - list_for_each_entry(t, &s->post_select_list, post_select_node) + list_for_each_entry(t, &s->task_list, node) task_notify(t, err); }