/*
- * Copyright (C) 2006-2009 Andre Noll <maan@systemlinux.org>
+ * Copyright (C) 2006-2010 Andre Noll <maan@systemlinux.org>
*
* Licensed under the GPL v2. For licencing details see COPYING.
*/
static struct timeval now_struct;
struct timeval *now = &now_struct;
-/**
+/*
* Remove a task from the scheduler.
*
* \param t The task to remove.
return -E_NOT_INITIALIZED;
if (!s->select_function)
s->select_function = para_select;
- gettimeofday(now, NULL);
again:
FD_ZERO(&s->rfds);
FD_ZERO(&s->wfds);
s->timeout = s->default_timeout;
s->max_fileno = -1;
+ gettimeofday(now, NULL);
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);
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))
goto again;
}
-/**
+/*
* Initialize the paraslash scheduler.
*/
static void init_sched(void)
*
* 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)
{
}
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);
+}