net: fix broken dccp_available_ccids()
[paraslash.git] / sched.c
diff --git a/sched.c b/sched.c
index bd98a51..4c9f14a 100644 (file)
--- a/sched.c
+++ b/sched.c
@@ -1,4 +1,16 @@
+/*
+ * Copyright (C) 2006-2009 Andre Noll <maan@systemlinux.org>
+ *
+ * Licensed under the GPL v2. For licencing details see COPYING.
+ */
+
+/** \file sched.c Paraslash's scheduling functions. */
+
+#include <regex.h>
+#include <dirent.h> /* readdir() */
+#include <assert.h>
 #include <sys/time.h>
+
 #include "para.h"
 #include "ipc.h"
 #include "fd.h"
 #include "string.h"
 #include "error.h"
 
-struct list_head pre_select_list;
-struct list_head post_select_list;
+static struct list_head pre_select_list, post_select_list;
+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.
+ *
+ * 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)
+{
+       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;
+}
+
 
 static void sched_preselect(struct sched *s)
 {
        struct task *t, *tmp;
-again:
        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->ret > 0)
-                       continue;
-               if (!t->event_handler)
+               if (t->error >= 0)
                        continue;
-               t->event_handler(t);
-               goto again;
+               /*
+                * 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);
        }
 }
 
@@ -31,85 +73,141 @@ 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->ret > 0 || !t->event_handler)
+               if (t->error >= 0)
                        continue;
-               t->event_handler(t);
+               /* nec., see sched_preselect() */
+               if (list_empty(&post_select_list))
+                       return;
+               unregister_task(t);
        }
 }
 
-int sched(struct sched *s)
+/**
+ * The core function for all paraslash programs.
+ *
+ * \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
+ * 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.
+ *
+ * \sa task, now.
+ */
+int schedule(struct sched *s)
 {
+       int ret;
 
-       gettimeofday(&s->now, NULL);
+       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->max_fileno = -1;
+       gettimeofday(now, NULL);
        sched_preselect(s);
-       s->select_ret = para_select(s->max_fileno + 1, &s->rfds,
-               &s->wfds, &s->timeout);
-       if (s->select_ret < 0)
-               return s->select_ret;
-       gettimeofday(&s->now, NULL);
+       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))
                return 0;
        goto again;
 }
 
-void *register_task(struct task *t)
+/*
+ * Initialize the paraslash scheduler.
+ */
+static void init_sched(void)
 {
+       PARA_INFO_LOG("initializing scheduler\n");
+       INIT_LIST_HEAD(&pre_select_list);
+       INIT_LIST_HEAD(&post_select_list);
+       initialized = 1;
+}
+
+/**
+ * Add a task to the scheduler.
+ *
+ * \param t the task to add
+ *
+ * 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.
+ *
+ * \sa task::pre_select, task::post_select
+ */
+void register_task(struct task *t)
+{
+       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);
-               if (t->flags & PRE_ADD_TAIL)
-                       list_add_tail(&t->pre_select_node, &pre_select_list);
-               else
-                       list_add(&t->pre_select_node, &pre_select_list);
+               list_add_tail(&t->pre_select_node, &pre_select_list);
        }
        if (t->post_select) {
-               PARA_DEBUG_LOG("post_select: %p\n", &t->pre_select);
-               if (t->flags & POST_ADD_TAIL)
-                       list_add_tail(&t->post_select_node, &post_select_list);
-               else
-                       list_add(&t->post_select_node, &post_select_list);
+               PARA_DEBUG_LOG("post_select: %p\n", &t->post_select);
+               list_add_tail(&t->post_select_node, &post_select_list);
        }
-       return t;
 }
 
-void unregister_task(struct task *t)
-{
-       PARA_INFO_LOG("unregistering %s (%p)\n", t->status, t);
-       if (t->pre_select)
-               list_del(&t->pre_select_node);
-       if (t->post_select)
-               list_del(&t->post_select_node);
-};
-
-void init_sched(void)
-{
-       INIT_LIST_HEAD(&pre_select_list);
-       INIT_LIST_HEAD(&post_select_list);
-};
-
+/**
+ * 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.
+ */
 void sched_shutdown(void)
 {
        struct task *t, *tmp;
 
+       if (!initialized)
+               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.
+ *
+ * \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 is dynamically allocated and must be freed by the caller.
+ */
 char *get_task_list(void)
 {
        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);
@@ -128,27 +226,122 @@ char *get_task_list(void)
        return msg;
 }
 
+/**
+ * Simulate an error for the given task.
+ *
+ * \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.
+ *
+ * \return Positive on success, negative on errors (e.g. if \a id does not
+ * correspond to a registered task).
+ */
 int kill_task(char *id)
 {
        struct task *t, *tmp;
        char buf[20];
+
+       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->ret = -E_TASK_KILLED;
-               if (t->event_handler)
-                       t->event_handler(t);
+               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->ret = -E_TASK_KILLED;
-               if (t->event_handler)
-                       t->event_handler(t);
+               t->error = -E_TASK_KILLED;
                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);
+}