-/*
- * Copyright (C) 2006-2014 Andre Noll <maan@systemlinux.org>
- *
- * Licensed under the GPL v2. For licencing details see COPYING.
- */
+/* Copyright (C) 2006 Andre Noll <maan@tuebingen.mpg.de>, see file COPYING. */
/** \file sched.c Paraslash's scheduling functions. */
#include <regex.h>
-#include <assert.h>
#include "para.h"
#include "ipc.h"
#include "time.h"
#include "error.h"
+/**
+ * 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;
- /** Whether this task is active (>=0) or in error state (<0). */
+ /* 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;
- /** True if task is in error state and exit status has been queried. */
- bool dead;
};
static struct timeval now_struct;
-struct timeval *now = &now_struct;
-
-static inline bool timeout_is_zero(struct sched *s)
-{
- struct timeval *tv = &s->select_timeout;
- return tv->tv_sec == 0 && tv->tv_usec == 0;
-}
+const struct timeval *now = &now_struct;
static void sched_preselect(struct sched *s)
{
if (t->notification != 0)
sched_min_delay(s);
if (t->info.pre_select)
- t->info.pre_select(s, t);
+ 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->name);
+ 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);
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->status = t->info.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->status = t->info.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);
PARA_WARNING_LOG("%s: post_select time: %lums\n",
t->name, pst);
#endif
+ t->status = ret < 0? ret : TS_RUNNING;
}
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->status < 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->status >= 0)
- num_running_tasks++;
}
return num_running_tasks;
}
* \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)
{
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);
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;
* \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.
*
int task_reap(struct task **tptr)
{
struct task *t;
+ int ret;
if (!tptr)
return 0;
return 0;
if (t->status >= 0)
return 0;
- if (t->dead) /* will be freed in sched_post_select() */
- 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->status;
+ return ret;
}
/**
struct task *t, *tmp;
list_for_each_entry_safe(t, tmp, &s->task_list, node) {
- if (t->status >= 0)
+ if (t->status == TS_RUNNING)
/* The task list should contain only terminated tasks. */
PARA_WARNING_LOG("shutting down running task %s\n",
t->name);
t->info = *info;
t->name = para_strdup(info->name);
t->notification = 0;
- t->status = 0;
- t->dead = false;
+ 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)
-{
- return t->info.context;
-}
-
/**
* Get the list of all registered tasks.
*
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->status < 0? (t->dead? "dead" : "zombie") : "running",
+ t->status == TS_DEAD? "dead" :
+ (t->status == TS_RUNNING? "running" : "zombie"),
t->name);
free(msg);
msg = tmp_msg;
{
if (!t)
return 0;
- if (t->dead)
+ if (t->status == TS_DEAD) /* pretend dead tasks don't exist */
return 0;
- if (t->status >= 0)
+ if (t->status == TS_RUNNING)
return 1;
return t->status;
}
* 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)
{
* \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)
{
* \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)
{
projects / paraslash.git / blobdiff