+/**
+ * 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->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->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->select_timeout.tv_sec = 0;
+ s->select_timeout.tv_usec = 1;
+}
+
+/**
+ * Impose an upper bound for the timeout of the next select() call.
+ *
+ * \param to Maximal allowed timeout.
+ * \param s Pointer to the scheduler struct.
+ *
+ * If the current scheduler timeout is already smaller than \a to, 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 *to, struct sched *s)
+{
+ if (tv_diff(&s->select_timeout, to, NULL) > 0)
+ s->select_timeout = *to;
+}
+
+/**
+ * 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);
+}