X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=sched.c;h=a2903940fdaea1b24d6a49cfc2f54766c136070f;hp=fe57e03eae01a1d4360ae41cdf61f893a9888128;hb=0c7c4d80673854527ce3c3786dd581169565b5e6;hpb=deb3326320166531abc35ce805dee4df6b49e936 diff --git a/sched.c b/sched.c index fe57e03e..a2903940 100644 --- a/sched.c +++ b/sched.c @@ -1,13 +1,8 @@ -/* - * Copyright (C) 2006-2014 Andre Noll - * - * Licensed under the GPL v2. For licencing details see COPYING. - */ +/* Copyright (C) 2006 Andre Noll , see file COPYING. */ /** \file sched.c Paraslash's scheduling functions. */ #include -#include #include "para.h" #include "ipc.h" @@ -18,55 +13,85 @@ #include "time.h" #include "error.h" -static struct timeval now_struct; -struct timeval *now = &now_struct; +/** + * 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 inline bool timeout_is_zero(struct sched *s) -{ - struct timeval *tv = &s->select_timeout; - return tv->tv_sec == 0 && tv->tv_usec == 0; -} +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->task_list, node) { - if (t->error < 0) + 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->status); + PARA_INFO_LOG("freeing task %s (%s)\n", t->name, t->status < 0? + para_strerror(-t->status) : + (t->status == TS_DEAD? "[dead]" : "[running]")); + list_del(&t->node); - if (t->owned_by_sched) - free(t); + 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 unsigned sched_post_select(struct sched *s) @@ -75,18 +100,14 @@ static unsigned sched_post_select(struct sched *s) unsigned num_running_tasks = 0; list_for_each_entry_safe(t, tmp, &s->task_list, node) { - if (t->error < 0) { - if (t->dead) /* task has been reaped */ - unlink_and_free_task(t); - continue; + 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++; } - call_post_select(s, t); - t->notification = 0; - if (t->error < 0) { - if (!t->owned_by_sched) - list_del(&t->node); - } else - num_running_tasks++; } return num_running_tasks; } @@ -104,7 +125,7 @@ static unsigned sched_post_select(struct sched *s) * \return Zero if no more tasks are left in the task list, negative if the * select function returned an error. * - * \sa \ref task, \ref now. + * \sa \ref now. */ int schedule(struct sched *s) { @@ -118,7 +139,7 @@ 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); @@ -134,7 +155,7 @@ again: FD_ZERO(&s->rfds); FD_ZERO(&s->wfds); } - clock_get_realtime(now); + clock_get_realtime(&now_struct); num_running_tasks = sched_post_select(s); if (num_running_tasks == 0) return 0; @@ -147,7 +168,7 @@ again: * \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 + * terminated task which allows releasing the resources associated with the * task. Until this function is called, the terminated task remains in a zombie * state. * @@ -163,29 +184,28 @@ again: int task_reap(struct task **tptr) { struct task *t; + int ret; if (!tptr) return 0; t = *tptr; if (!t) return 0; - if (!t->owned_by_sched) - return 0; - if (t->error >= 0) - return 0; - if (t->dead) /* will be freed in sched_post_select() */ + 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 t->dead which tells schedule() to free the task in - * the next iteration of its loop. + * 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->dead = true; + t->status = TS_DEAD; + *tptr = NULL; - return t->error; + return ret; } /** @@ -200,10 +220,10 @@ void sched_shutdown(struct sched *s) struct task *t, *tmp; list_for_each_entry_safe(t, tmp, &s->task_list, node) { - if (t->error >= 0) + if (t->status == TS_RUNNING) /* The task list should contain only terminated tasks. */ PARA_WARNING_LOG("shutting down running task %s\n", - t->status); + t->name); unlink_and_free_task(t); } } @@ -226,33 +246,14 @@ struct task *task_register(struct task_info *info, struct sched *s) if (!s->task_list.next) INIT_LIST_HEAD(&s->task_list); - snprintf(t->status, sizeof(t->status) - 1, "%s", info->name); - t->status[sizeof(t->status) - 1] = '\0'; + t->info = *info; + t->name = para_strdup(info->name); t->notification = 0; - t->error = 0; - t->dead = false; - t->pre_select = info->pre_select; - t->post_select = info->post_select; - t->context = info->context; - t->owned_by_sched = true; + 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) -{ - assert(t->owned_by_sched); - return t->context; -} - /** * Get the list of all registered tasks. * @@ -271,8 +272,9 @@ char *get_task_list(struct sched *s) list_for_each_entry_safe(t, tmp, &s->task_list, node) { char *tmp_msg; tmp_msg = make_message("%s%p\t%s\t%s\n", msg? msg : "", t, - t->error < 0? (t->dead? "dead" : "zombie") : "running", - t->status); + t->status == TS_DEAD? "dead" : + (t->status == TS_RUNNING? "running" : "zombie"), + t->name); free(msg); msg = tmp_msg; } @@ -303,7 +305,7 @@ 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; } @@ -323,6 +325,25 @@ 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. * @@ -362,7 +383,7 @@ void sched_min_delay(struct sched *s) * function does nothing. Otherwise the timeout for the next select() call is * set to the given value. * - * \sa sched_request_timeout_ms(). + * \sa \ref sched_request_timeout_ms(). */ void sched_request_timeout(struct timeval *to, struct sched *s) { @@ -395,7 +416,7 @@ void sched_request_timeout_ms(long unsigned ms, struct sched *s) * \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(). + * \sa \ref sched_request_barrier_or_min_delay(). */ int sched_request_barrier(struct timeval *barrier, struct sched *s) { @@ -416,7 +437,7 @@ int sched_request_barrier(struct timeval *barrier, struct sched *s) * \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(). + * \sa \ref sched_min_delay(), \ref sched_request_barrier(). */ int sched_request_barrier_or_min_delay(struct timeval *barrier, struct sched *s) {