X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=sched.c;h=4c9f14a8001abe415e378b4f890c774e8cfc58c2;hp=9976a11d2aa315f78ff88072c0a27d84ed35e58d;hb=23f053fc0a392079213bf2f979b7c098baa9d30c;hpb=335730538150250f32c0df0b184fb494e2bb0df3 diff --git a/sched.c b/sched.c index 9976a11d..4c9f14a8 100644 --- a/sched.c +++ b/sched.c @@ -1,11 +1,12 @@ /* - * Copyright (C) 2006-2008 Andre Noll + * Copyright (C) 2006-2009 Andre Noll * * Licensed under the GPL v2. For licencing details see COPYING. */ -/** \file sched.c paraslash's scheduling functions */ +/** \file sched.c Paraslash's scheduling functions. */ +#include #include /* readdir() */ #include #include @@ -24,34 +25,45 @@ static int initialized; static struct timeval now_struct; struct timeval *now = &now_struct; -/** +/* * Remove a task from the scheduler. * - * \param t the task to remove + * \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. */ -void unregister_task(struct task *t) +static void unregister_task(struct task *t) { if (!initialized) return; - PARA_INFO_LOG("unregistering %s (%p)\n", t->status, t); + 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; +} static void sched_preselect(struct sched *s) { struct task *t, *tmp; list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) { - t->pre_select(s, t); + if (t->error >= 0 && t->pre_select) + t->pre_select(s, t); // PARA_INFO_LOG("%s \n", t->status); if (t->error >= 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); } } @@ -61,18 +73,22 @@ static void sched_post_select(struct sched *s) struct task *t, *tmp; list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) { - t->post_select(s, t); + 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); } } /** - * the core function for all paraslash programs + * The core function for all paraslash programs. * - * \param s pointer to the scheduler struct + * \param s Pointer to the scheduler struct. * * This function updates the global \a now pointer, calls all registered * pre_select hooks which may set the timeout and add any file descriptors to @@ -90,16 +106,30 @@ int schedule(struct sched *s) if (!initialized) return -E_NOT_INITIALIZED; - gettimeofday(now, NULL); + if (!s->select_function) + s->select_function = para_select; again: FD_ZERO(&s->rfds); FD_ZERO(&s->wfds); s->timeout = s->default_timeout; s->max_fileno = -1; + gettimeofday(now, NULL); sched_preselect(s); - ret = para_select(s->max_fileno + 1, &s->rfds, &s->wfds, &s->timeout); + 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); if (ret < 0) return ret; + if (ret == 0) { + /* + * APUE: Be careful not to check the descriptor sets on return + * unless the return value is greater than zero. The return + * state of the descriptor sets is implementation dependent if + * either a signal is caught or the timer expires. + */ + 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)) @@ -107,8 +137,8 @@ again: goto again; } -/** - * initialize the paraslash scheduler +/* + * Initialize the paraslash scheduler. */ static void init_sched(void) { @@ -116,10 +146,10 @@ static void init_sched(void) INIT_LIST_HEAD(&pre_select_list); INIT_LIST_HEAD(&post_select_list); initialized = 1; -}; +} /** - * add a task to the scheduler + * Add a task to the scheduler. * * \param t the task to add * @@ -138,13 +168,13 @@ void register_task(struct task *t) list_add_tail(&t->pre_select_node, &pre_select_list); } if (t->post_select) { - PARA_DEBUG_LOG("post_select: %p\n", &t->pre_select); + PARA_DEBUG_LOG("post_select: %p\n", &t->post_select); list_add_tail(&t->post_select_node, &post_select_list); } } /** - * unregister all tasks + * Unregister all tasks. * * This will cause \a schedule() to return immediately because both the * \a pre_select_list and the \a post_select_list are empty. @@ -157,20 +187,19 @@ void sched_shutdown(void) return; list_for_each_entry_safe(t, tmp, &pre_select_list, pre_select_node) unregister_task(t); - /* remove tasks which do not have a pre_select hook */ list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) unregister_task(t); initialized = 0; -}; +} /** - * get the list of all registered tasks. + * Get the list of all registered tasks. * - * \return the task list + * \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. + * The result is dynamically allocated and must be freed by the caller. */ char *get_task_list(void) { @@ -198,9 +227,9 @@ char *get_task_list(void) } /** - * simulate an error for the given task + * Simulate an error for the given task. * - * \param id the task identifier + * \param id The task identifier. * * Find the task identified by \a id, set the tasks' error value to * \p -E_TASK_KILLED and unregister the task. @@ -220,7 +249,6 @@ int kill_task(char *id) if (strcmp(id, buf)) continue; t->error = -E_TASK_KILLED; - unregister_task(t); return 1; } list_for_each_entry_safe(t, tmp, &post_select_list, post_select_node) { @@ -228,8 +256,92 @@ int kill_task(char *id) if (strcmp(id, buf)) continue; t->error = -E_TASK_KILLED; - unregister_task(t); return 1; } return -E_NO_SUCH_TASK; } + +/** + * 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; +} + +/** + * Impose an upper bound for the timeout of the next select() call. + * + * \param timeout Maximal allowed timeout. + * \param s Pointer to the scheduler struct. + * + * If the current scheduler timeout is already smaller than \a timeout, 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 *timeout, struct sched *s) +{ + if (tv_diff(&s->timeout, timeout, NULL) > 0) + s->timeout = *timeout; +} + +/** + * 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; + ms2tv(ms, &tv); + sched_request_timeout(&tv, 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. + * + * If \a barrier is in the past, this function does nothing. + * + * \sa sched_request_barrier_or_min_delay(). + */ +void sched_request_barrier(struct timeval *barrier, struct sched *s) +{ + struct timeval diff; + + if (tv_diff(now, barrier, &diff) > 0) + return; + sched_request_timeout(&diff, s); +} + +/** + * 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. + * + * If \a barrier is in the past, this function requests a minimal timeout. + * + * \sa sched_min_delay(), sched_request_barrier(). + */ +void sched_request_barrier_or_min_delay(struct timeval *barrier, struct sched *s) +{ + struct timeval diff; + + if (tv_diff(now, barrier, &diff) > 0) + return sched_min_delay(s); + sched_request_timeout(&diff, s); +}