task.c revision 3be0a4382d6b0e9f9ecf2fa1f2e9154087f3a175
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt/*
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt * Copyright (C) 1998-2000 Internet Software Consortium.
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt *
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt * Permission to use, copy, modify, and distribute this software for any
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt * purpose with or without fee is hereby granted, provided that the above
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt * copyright notice and this permission notice appear in all copies.
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt *
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM
44931133ff16d6da48a1823b12dc4cfddf619412Automatic Updater * DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt * INTERNET SOFTWARE CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT,
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt * FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt * NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
44931133ff16d6da48a1823b12dc4cfddf619412Automatic Updater * WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt */
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt/* $Id: task.c,v 1.72 2000/08/29 22:30:14 bwelling Exp $ */
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt/*
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt * Principal Author: Bob Halley
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt */
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt/*
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt * XXXRTH Need to document the states a task can be in, and the rules
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt * for changing states.
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt */
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt#include <config.h>
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt#include <isc/condition.h>
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt#include <isc/event.h>
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt#include <isc/mem.h>
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt#include <isc/string.h>
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt#include <isc/task.h>
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt#include <isc/thread.h>
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt#include <isc/util.h>
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt#ifndef ISC_PLATFORM_USETHREADS
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt#include "task_p.h"
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt#endif
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt#define ISC_TASK_NAMES 1
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt#ifdef ISC_TASK_TRACE
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt#define XTRACE(m) fprintf(stderr, "task %p thread %lu: %s\n", \
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt task, isc_thread_self(), (m))
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt#define XTTRACE(t, m) fprintf(stderr, "task %p thread %lu: %s\n", \
64c66c801f5a23f2050b263819181e6f6c6c108aEvan Hunt (t), isc_thread_self(), (m))
#define XTHREADTRACE(m) fprintf(stderr, "thread %lu: %s\n", \
isc_thread_self(), (m))
#else
#define XTRACE(m)
#define XTTRACE(t, m)
#define XTHREADTRACE(m)
#endif
/***
*** Types.
***/
typedef enum {
task_state_idle, task_state_ready, task_state_running,
task_state_done
} task_state_t;
#define TASK_MAGIC 0x5441534BU /* TASK. */
#define VALID_TASK(t) ((t) != NULL && \
(t)->magic == TASK_MAGIC)
struct isc_task {
/* Not locked. */
unsigned int magic;
isc_taskmgr_t * manager;
isc_mutex_t lock;
/* Locked by task lock. */
task_state_t state;
unsigned int references;
isc_eventlist_t events;
isc_eventlist_t on_shutdown;
unsigned int quantum;
unsigned int flags;
#ifdef ISC_TASK_NAMES
char name[16];
void * tag;
#endif
/* Locked by task manager lock. */
LINK(isc_task_t) link;
LINK(isc_task_t) ready_link;
};
#define TASK_F_SHUTTINGDOWN 0x01
#define TASK_SHUTTINGDOWN(t) (((t)->flags & TASK_F_SHUTTINGDOWN) \
!= 0)
#define TASK_MANAGER_MAGIC 0x54534B4DU /* TSKM. */
#define VALID_MANAGER(m) ((m) != NULL && \
(m)->magic == TASK_MANAGER_MAGIC)
struct isc_taskmgr {
/* Not locked. */
unsigned int magic;
isc_mem_t * mctx;
isc_mutex_t lock;
unsigned int workers;
#ifdef ISC_PLATFORM_USETHREADS
isc_thread_t * threads;
#endif
/* Locked by task manager lock. */
unsigned int default_quantum;
LIST(isc_task_t) tasks;
LIST(isc_task_t) ready_tasks;
#ifdef ISC_PLATFORM_USETHREADS
isc_condition_t work_available;
#endif
isc_boolean_t exiting;
#ifndef ISC_PLATFORM_USETHREADS
unsigned int refs;
#endif
};
#define DEFAULT_DEFAULT_QUANTUM 5
#define FINISHED(m) ((m)->exiting && EMPTY((m)->tasks))
#ifndef ISC_PLATFORM_USETHREADS
static isc_taskmgr_t *taskmgr = NULL;
#endif
/***
*** Tasks.
***/
static void
task_finished(isc_task_t *task) {
isc_taskmgr_t *manager = task->manager;
REQUIRE(EMPTY(task->events));
REQUIRE(EMPTY(task->on_shutdown));
REQUIRE(task->references == 0);
REQUIRE(task->state == task_state_done);
XTRACE("task_finished");
LOCK(&manager->lock);
UNLINK(manager->tasks, task, link);
#ifdef ISC_PLATFORM_USETHREADS
if (FINISHED(manager)) {
/*
* All tasks have completed and the
* task manager is exiting. Wake up
* any idle worker threads so they
* can exit.
*/
BROADCAST(&manager->work_available);
}
#endif
UNLOCK(&manager->lock);
DESTROYLOCK(&task->lock);
task->magic = 0;
isc_mem_put(manager->mctx, task, sizeof *task);
}
isc_result_t
isc_task_create(isc_taskmgr_t *manager, unsigned int quantum,
isc_task_t **taskp)
{
isc_task_t *task;
isc_boolean_t exiting;
REQUIRE(VALID_MANAGER(manager));
REQUIRE(taskp != NULL && *taskp == NULL);
task = isc_mem_get(manager->mctx, sizeof *task);
if (task == NULL)
return (ISC_R_NOMEMORY);
XTRACE("create");
task->manager = manager;
if (isc_mutex_init(&task->lock) != ISC_R_SUCCESS) {
isc_mem_put(manager->mctx, task, sizeof *task);
UNEXPECTED_ERROR(__FILE__, __LINE__,
"isc_mutex_init() failed");
return (ISC_R_UNEXPECTED);
}
task->state = task_state_idle;
task->references = 1;
INIT_LIST(task->events);
INIT_LIST(task->on_shutdown);
task->quantum = quantum;
task->flags = 0;
#ifdef ISC_TASK_NAMES
memset(task->name, 0, sizeof task->name);
task->tag = NULL;
#endif
INIT_LINK(task, link);
INIT_LINK(task, ready_link);
exiting = ISC_FALSE;
LOCK(&manager->lock);
if (!manager->exiting) {
if (task->quantum == 0)
task->quantum = manager->default_quantum;
APPEND(manager->tasks, task, link);
} else
exiting = ISC_TRUE;
UNLOCK(&manager->lock);
if (exiting) {
DESTROYLOCK(&task->lock);
isc_mem_put(manager->mctx, task, sizeof *task);
return (ISC_R_SHUTTINGDOWN);
}
task->magic = TASK_MAGIC;
*taskp = task;
return (ISC_R_SUCCESS);
}
void
isc_task_attach(isc_task_t *source, isc_task_t **targetp) {
/*
* Attach *targetp to source.
*/
REQUIRE(VALID_TASK(source));
REQUIRE(targetp != NULL && *targetp == NULL);
XTTRACE(source, "attach");
LOCK(&source->lock);
source->references++;
UNLOCK(&source->lock);
*targetp = source;
}
static inline isc_boolean_t
task_shutdown(isc_task_t *task) {
isc_boolean_t was_idle = ISC_FALSE;
isc_event_t *event, *prev;
/*
* Caller must be holding the task's lock.
*/
XTRACE("task_shutdown");
if (! TASK_SHUTTINGDOWN(task)) {
XTRACE("shutting down");
task->flags |= TASK_F_SHUTTINGDOWN;
if (task->state == task_state_idle) {
INSIST(EMPTY(task->events));
task->state = task_state_ready;
was_idle = ISC_TRUE;
}
INSIST(task->state == task_state_ready ||
task->state == task_state_running);
/*
* Note that we post shutdown events LIFO.
*/
for (event = TAIL(task->on_shutdown);
event != NULL;
event = prev) {
prev = PREV(event, ev_link);
DEQUEUE(task->on_shutdown, event, ev_link);
ENQUEUE(task->events, event, ev_link);
}
}
return (was_idle);
}
static inline void
task_ready(isc_task_t *task) {
isc_taskmgr_t *manager = task->manager;
REQUIRE(VALID_MANAGER(manager));
REQUIRE(task->state == task_state_ready);
XTRACE("task_ready");
LOCK(&manager->lock);
ENQUEUE(manager->ready_tasks, task, ready_link);
#ifdef ISC_PLATFORM_USETHREADS
SIGNAL(&manager->work_available);
#endif
UNLOCK(&manager->lock);
}
static inline isc_boolean_t
task_detach(isc_task_t *task) {
/*
* Caller must be holding the task lock.
*/
REQUIRE(task->references > 0);
XTRACE("detach");
task->references--;
if (task->references == 0 && task->state == task_state_idle) {
INSIST(EMPTY(task->events));
/*
* There are no references to this task, and no
* pending events. We could try to optimize and
* either initiate shutdown or clean up the task,
* depending on its state, but it's easier to just
* make the task ready and allow run() or the event
* loop to deal with shutting down and termination.
*/
task->state = task_state_ready;
return (ISC_TRUE);
}
return (ISC_FALSE);
}
void
isc_task_detach(isc_task_t **taskp) {
isc_task_t *task;
isc_boolean_t was_idle;
/*
* Detach *taskp from its task.
*/
REQUIRE(taskp != NULL);
task = *taskp;
REQUIRE(VALID_TASK(task));
XTRACE("isc_task_detach");
LOCK(&task->lock);
was_idle = task_detach(task);
UNLOCK(&task->lock);
if (was_idle)
task_ready(task);
*taskp = NULL;
}
static inline isc_boolean_t
task_send(isc_task_t *task, isc_event_t **eventp) {
isc_boolean_t was_idle = ISC_FALSE;
isc_event_t *event;
/*
* Caller must be holding the task lock.
*/
REQUIRE(eventp != NULL);
event = *eventp;
REQUIRE(event != NULL);
REQUIRE(event->ev_type > 0);
REQUIRE(task->state != task_state_done);
XTRACE("task_send");
if (task->state == task_state_idle) {
was_idle = ISC_TRUE;
INSIST(EMPTY(task->events));
task->state = task_state_ready;
}
INSIST(task->state == task_state_ready ||
task->state == task_state_running);
ENQUEUE(task->events, event, ev_link);
*eventp = NULL;
return (was_idle);
}
void
isc_task_send(isc_task_t *task, isc_event_t **eventp) {
isc_boolean_t was_idle;
/*
* Send '*event' to 'task'.
*/
REQUIRE(VALID_TASK(task));
XTRACE("isc_task_send");
/*
* We're trying hard to hold locks for as short a time as possible.
* We're also trying to hold as few locks as possible. This is why
* some processing is deferred until after the lock is released.
*/
LOCK(&task->lock);
was_idle = task_send(task, eventp);
UNLOCK(&task->lock);
if (was_idle) {
/*
* We need to add this task to the ready queue.
*
* We've waited until now to do it because making a task
* ready requires locking the manager. If we tried to do
* this while holding the task lock, we could deadlock.
*
* We've changed the state to ready, so no one else will
* be trying to add this task to the ready queue. The
* only way to leave the ready state is by executing the
* task. It thus doesn't matter if events are added,
* removed, or a shutdown is started in the interval
* between the time we released the task lock, and the time
* we add the task to the ready queue.
*/
task_ready(task);
}
}
void
isc_task_sendanddetach(isc_task_t **taskp, isc_event_t **eventp) {
isc_boolean_t idle1, idle2;
isc_task_t *task;
/*
* Send '*event' to '*taskp' and then detach '*taskp' from its
* task.
*/
REQUIRE(taskp != NULL);
task = *taskp;
REQUIRE(VALID_TASK(task));
XTRACE("isc_task_sendanddetach");
LOCK(&task->lock);
idle1 = task_send(task, eventp);
idle2 = task_detach(task);
UNLOCK(&task->lock);
/*
* If idle1, then idle2 shouldn't be true as well since we're holding
* the task lock, and thus the task cannot switch from ready back to
* idle.
*/
INSIST(!(idle1 && idle2));
if (idle1 || idle2)
task_ready(task);
*taskp = NULL;
}
#define PURGE_OK(event) (((event)->ev_attributes & ISC_EVENTATTR_NOPURGE) == 0)
static unsigned int
dequeue_events(isc_task_t *task, void *sender, isc_eventtype_t first,
isc_eventtype_t last, void *tag,
isc_eventlist_t *events, isc_boolean_t purging)
{
isc_event_t *event, *next_event;
unsigned int count = 0;
REQUIRE(VALID_TASK(task));
REQUIRE(last >= first);
XTRACE("dequeue_events");
/*
* Events matching 'sender', whose type is >= first and <= last, and
* whose tag is 'tag' will be dequeued. If 'purging', matching events
* which are marked as unpurgable will not be dequeued.
*
* sender == NULL means "any sender", and tag == NULL means "any tag".
*/
LOCK(&task->lock);
for (event = HEAD(task->events); event != NULL; event = next_event) {
next_event = NEXT(event, ev_link);
if (event->ev_type >= first && event->ev_type <= last &&
(sender == NULL || event->ev_sender == sender) &&
(tag == NULL || event->ev_tag == tag) &&
(!purging || PURGE_OK(event))) {
DEQUEUE(task->events, event, ev_link);
ENQUEUE(*events, event, ev_link);
count++;
}
}
UNLOCK(&task->lock);
return (count);
}
unsigned int
isc_task_purgerange(isc_task_t *task, void *sender, isc_eventtype_t first,
isc_eventtype_t last, void *tag)
{
unsigned int count;
isc_eventlist_t events;
isc_event_t *event, *next_event;
/*
* Purge events from a task's event queue.
*/
XTRACE("isc_task_purgerange");
ISC_LIST_INIT(events);
count = dequeue_events(task, sender, first, last, tag, &events,
ISC_TRUE);
for (event = HEAD(events); event != NULL; event = next_event) {
next_event = NEXT(event, ev_link);
isc_event_free(&event);
}
/*
* Note that purging never changes the state of the task.
*/
return (count);
}
unsigned int
isc_task_purge(isc_task_t *task, void *sender, isc_eventtype_t type,
void *tag)
{
/*
* Purge events from a task's event queue.
*/
XTRACE("isc_task_purge");
return (isc_task_purgerange(task, sender, type, type, tag));
}
isc_boolean_t
isc_task_purgeevent(isc_task_t *task, isc_event_t *event) {
isc_event_t *curr_event, *next_event;
/*
* Purge 'event' from a task's event queue.
*
* XXXRTH: WARNING: This method may be removed before beta.
*/
REQUIRE(VALID_TASK(task));
/*
* If 'event' is on the task's event queue, it will be purged,
* unless it is marked as unpurgeable. 'event' does not have to be
* on the task's event queue; in fact, it can even be an invalid
* pointer. Purging only occurs if the event is actually on the task's
* event queue.
*
* Purging never changes the state of the task.
*/
LOCK(&task->lock);
for (curr_event = HEAD(task->events);
curr_event != NULL;
curr_event = next_event) {
next_event = NEXT(curr_event, ev_link);
if (curr_event == event && PURGE_OK(event)) {
DEQUEUE(task->events, curr_event, ev_link);
break;
}
}
UNLOCK(&task->lock);
if (curr_event == NULL)
return (ISC_FALSE);
isc_event_free(&curr_event);
return (ISC_TRUE);
}
unsigned int
isc_task_unsendrange(isc_task_t *task, void *sender, isc_eventtype_t first,
isc_eventtype_t last, void *tag,
isc_eventlist_t *events)
{
/*
* Remove events from a task's event queue.
*/
XTRACE("isc_task_unsendrange");
return (dequeue_events(task, sender, first, last, tag, events,
ISC_FALSE));
}
unsigned int
isc_task_unsend(isc_task_t *task, void *sender, isc_eventtype_t type,
void *tag, isc_eventlist_t *events)
{
/*
* Remove events from a task's event queue.
*/
XTRACE("isc_task_unsend");
return (dequeue_events(task, sender, type, type, tag, events,
ISC_FALSE));
}
isc_result_t
isc_task_onshutdown(isc_task_t *task, isc_taskaction_t action, const void *arg)
{
isc_boolean_t disallowed = ISC_FALSE;
isc_result_t result = ISC_R_SUCCESS;
isc_event_t *event;
/*
* Send a shutdown event with action 'action' and argument 'arg' when
* 'task' is shutdown.
*/
REQUIRE(VALID_TASK(task));
REQUIRE(action != NULL);
event = isc_event_allocate(task->manager->mctx,
NULL,
ISC_TASKEVENT_SHUTDOWN,
action,
arg,
sizeof *event);
if (event == NULL)
return (ISC_R_NOMEMORY);
LOCK(&task->lock);
if (TASK_SHUTTINGDOWN(task)) {
disallowed = ISC_TRUE;
result = ISC_R_SHUTTINGDOWN;
} else
ENQUEUE(task->on_shutdown, event, ev_link);
UNLOCK(&task->lock);
if (disallowed)
isc_mem_put(task->manager->mctx, event, sizeof *event);
return (result);
}
void
isc_task_shutdown(isc_task_t *task) {
isc_boolean_t was_idle;
/*
* Shutdown 'task'.
*/
REQUIRE(VALID_TASK(task));
LOCK(&task->lock);
was_idle = task_shutdown(task);
UNLOCK(&task->lock);
if (was_idle)
task_ready(task);
}
void
isc_task_destroy(isc_task_t **taskp) {
/*
* Destroy '*taskp'.
*/
REQUIRE(taskp != NULL);
isc_task_shutdown(*taskp);
isc_task_detach(taskp);
}
void
isc_task_setname(isc_task_t *task, const char *name, void *tag) {
/*
* Name 'task'.
*/
REQUIRE(VALID_TASK(task));
#ifdef ISC_TASK_NAMES
LOCK(&task->lock);
memset(task->name, 0, sizeof(task->name));
strncpy(task->name, name, sizeof(task->name) - 1);
task->tag = tag;
UNLOCK(&task->lock);
#else
(void)name;
(void)tag;
#endif
}
const char *
isc_task_getname(isc_task_t *task) {
return (task->name);
}
void *
isc_task_gettag(isc_task_t *task) {
return (task->tag);
}
/***
*** Task Manager.
***/
static void
dispatch(isc_taskmgr_t *manager) {
isc_task_t *task;
REQUIRE(VALID_MANAGER(manager));
/*
* Again we're trying to hold the lock for as short a time as possible
* and to do as little locking and unlocking as possible.
*
* In both while loops, the appropriate lock must be held before the
* while body starts. Code which acquired the lock at the top of
* the loop would be more readable, but would result in a lot of
* extra locking. Compare:
*
* Straightforward:
*
* LOCK();
* ...
* UNLOCK();
* while (expression) {
* LOCK();
* ...
* UNLOCK();
*
* Unlocked part here...
*
* LOCK();
* ...
* UNLOCK();
* }
*
* Note how if the loop continues we unlock and then immediately lock.
* For N iterations of the loop, this code does 2N+1 locks and 2N+1
* unlocks. Also note that the lock is not held when the while
* condition is tested, which may or may not be important, depending
* on the expression.
*
* As written:
*
* LOCK();
* while (expression) {
* ...
* UNLOCK();
*
* Unlocked part here...
*
* LOCK();
* ...
* }
* UNLOCK();
*
* For N iterations of the loop, this code does N+1 locks and N+1
* unlocks. The while expression is always protected by the lock.
*/
LOCK(&manager->lock);
#ifndef ISC_PLATFORM_USETHREADS
while (!EMPTY(manager->ready_tasks) && !FINISHED(manager)) {
#else
while (!FINISHED(manager)) {
/*
* For reasons similar to those given in the comment in
* isc_task_send() above, it is safe for us to dequeue
* the task while only holding the manager lock, and then
* change the task to running state while only holding the
* task lock.
*/
while (EMPTY(manager->ready_tasks) && !FINISHED(manager)) {
XTHREADTRACE("wait");
WAIT(&manager->work_available, &manager->lock);
XTHREADTRACE("awake");
}
#endif
XTHREADTRACE("working");
task = HEAD(manager->ready_tasks);
if (task != NULL) {
unsigned int dispatch_count = 0;
isc_boolean_t done = ISC_FALSE;
isc_boolean_t requeue = ISC_FALSE;
isc_boolean_t finished = ISC_FALSE;
isc_event_t *event;
INSIST(VALID_TASK(task));
/*
* Note we only unlock the manager lock if we actually
* have a task to do. We must reacquire the manager
* lock before exiting the 'if (task != NULL)' block.
*/
DEQUEUE(manager->ready_tasks, task, ready_link);
UNLOCK(&manager->lock);
LOCK(&task->lock);
INSIST(task->state == task_state_ready);
task->state = task_state_running;
XTRACE("running");
do {
if (!EMPTY(task->events)) {
event = HEAD(task->events);
DEQUEUE(task->events, event, ev_link);
/*
* Execute the event action.
*/
XTRACE("execute action");
if (event->ev_action != NULL) {
UNLOCK(&task->lock);
(event->ev_action)(task,event);
LOCK(&task->lock);
}
dispatch_count++;
}
if (task->references == 0 &&
EMPTY(task->events) &&
!TASK_SHUTTINGDOWN(task)) {
isc_boolean_t was_idle;
/*
* There are no references and no
* pending events for this task,
* which means it will not become
* runnable again via an external
* action (such as sending an event
* or detaching).
*
* We initiate shutdown to prevent
* it from becoming a zombie.
*
* We do this here instead of in
* the "if EMPTY(task->events)" block
* below because:
*
* If we post no shutdown events,
* we want the task to finish.
*
* If we did post shutdown events,
* will still want the task's
* quantum to be applied.
*/
was_idle = task_shutdown(task);
INSIST(!was_idle);
}
if (EMPTY(task->events)) {
/*
* Nothing else to do for this task
* right now.
*/
XTRACE("empty");
if (task->references == 0 &&
TASK_SHUTTINGDOWN(task)) {
/*
* The task is done.
*/
XTRACE("done");
finished = ISC_TRUE;
task->state = task_state_done;
} else
task->state = task_state_idle;
done = ISC_TRUE;
} else if (dispatch_count >= task->quantum) {
/*
* Our quantum has expired, but
* there is more work to be done.
* We'll requeue it to the ready
* queue later.
*
* We don't check quantum until
* dispatching at least one event,
* so the minimum quantum is one.
*/
XTRACE("quantum");
task->state = task_state_ready;
requeue = ISC_TRUE;
done = ISC_TRUE;
}
} while (!done);
UNLOCK(&task->lock);
if (finished)
task_finished(task);
LOCK(&manager->lock);
if (requeue) {
/*
* We know we're awake, so we don't have
* to wakeup any sleeping threads if the
* ready queue is empty before we requeue.
*
* A possible optimization if the queue is
* empty is to 'goto' the 'if (task != NULL)'
* block, avoiding the ENQUEUE of the task
* and the subsequent immediate DEQUEUE
* (since it is the only executable task).
* We don't do this because then we'd be
* skipping the exit_requested check. The
* cost of ENQUEUE is low anyway, especially
* when you consider that we'd have to do
* an extra EMPTY check to see if we could
* do the optimization. If the ready queue
* were usually nonempty, the 'optimization'
* might even hurt rather than help.
*/
ENQUEUE(manager->ready_tasks, task,
ready_link);
}
}
}
UNLOCK(&manager->lock);
}
#ifdef ISC_PLATFORM_USETHREADS
static isc_threadresult_t
#ifdef _WIN32
WINAPI
#endif
run(void *uap) {
isc_taskmgr_t *manager = uap;
XTHREADTRACE("start");
dispatch(manager);
XTHREADTRACE("exit");
return ((isc_threadresult_t)0);
}
#endif
static void
manager_free(isc_taskmgr_t *manager) {
isc_mem_t *mctx;
#ifdef ISC_PLATFORM_USETHREADS
(void)isc_condition_destroy(&manager->work_available);
isc_mem_put(manager->mctx, manager->threads,
manager->workers * sizeof (isc_thread_t));
#endif
DESTROYLOCK(&manager->lock);
manager->magic = 0;
mctx = manager->mctx;
isc_mem_put(mctx, manager, sizeof *manager);
isc_mem_detach(&mctx);
}
isc_result_t
isc_taskmgr_create(isc_mem_t *mctx, unsigned int workers,
unsigned int default_quantum, isc_taskmgr_t **managerp)
{
unsigned int i, started = 0;
isc_taskmgr_t *manager;
/*
* Create a new task manager.
*/
REQUIRE(workers > 0);
REQUIRE(managerp != NULL && *managerp == NULL);
#ifndef ISC_PLATFORM_USETHREADS
UNUSED(i);
UNUSED(started);
if (taskmgr != NULL) {
taskmgr->refs++;
*managerp = taskmgr;
return (ISC_R_SUCCESS);
}
#endif
manager = isc_mem_get(mctx, sizeof *manager);
if (manager == NULL)
return (ISC_R_NOMEMORY);
manager->magic = TASK_MANAGER_MAGIC;
manager->mctx = NULL;
manager->workers = 0;
if (isc_mutex_init(&manager->lock) != ISC_R_SUCCESS) {
isc_mem_put(mctx, manager, sizeof *manager);
UNEXPECTED_ERROR(__FILE__, __LINE__,
"isc_mutex_init() failed");
return (ISC_R_UNEXPECTED);
}
#ifdef ISC_PLATFORM_USETHREADS
manager->threads = isc_mem_get(mctx, workers * sizeof (isc_thread_t));
if (manager->threads == NULL) {
DESTROYLOCK(&manager->lock);
isc_mem_put(mctx, manager, sizeof *manager);
return (ISC_R_NOMEMORY);
}
if (isc_condition_init(&manager->work_available) != ISC_R_SUCCESS) {
DESTROYLOCK(&manager->lock);
isc_mem_put(mctx, manager->threads,
workers * sizeof (isc_thread_t));
isc_mem_put(mctx, manager, sizeof *manager);
UNEXPECTED_ERROR(__FILE__, __LINE__,
"isc_condition_init() failed");
return (ISC_R_UNEXPECTED);
}
#endif
if (default_quantum == 0)
default_quantum = DEFAULT_DEFAULT_QUANTUM;
manager->default_quantum = default_quantum;
INIT_LIST(manager->tasks);
INIT_LIST(manager->ready_tasks);
manager->exiting = ISC_FALSE;
manager->workers = 0;
isc_mem_attach(mctx, &manager->mctx);
#ifdef ISC_PLATFORM_USETHREADS
LOCK(&manager->lock);
/*
* Start workers.
*/
for (i = 0; i < workers; i++) {
if (isc_thread_create(run, manager,
&manager->threads[manager->workers]) ==
ISC_R_SUCCESS) {
manager->workers++;
started++;
}
}
UNLOCK(&manager->lock);
if (started == 0) {
manager_free(manager);
return (ISC_R_NOTHREADS);
}
#else
manager->refs = 0;
taskmgr = manager;
#endif
*managerp = manager;
return (ISC_R_SUCCESS);
}
void
isc_taskmgr_destroy(isc_taskmgr_t **managerp) {
isc_taskmgr_t *manager;
isc_task_t *task;
unsigned int i;
/*
* Destroy '*managerp'.
*/
REQUIRE(managerp != NULL);
manager = *managerp;
REQUIRE(VALID_MANAGER(manager));
#ifndef ISC_PLATFORM_USETHREADS
UNUSED(i);
if (manager->refs > 1) {
manager->refs--;
*managerp = NULL;
return;
}
#endif
XTHREADTRACE("isc_taskmgr_destroy");
/*
* Only one non-worker thread may ever call this routine.
* If a worker thread wants to initiate shutdown of the
* task manager, it should ask some non-worker thread to call
* isc_taskmgr_destroy(), e.g. by signalling a condition variable
* that the startup thread is sleeping on.
*/
/*
* Unlike elsewhere, we're going to hold this lock a long time.
* We need to do so, because otherwise the list of tasks could
* change while we were traversing it.
*
* This is also the only function where we will hold both the
* task manager lock and a task lock at the same time.
*/
LOCK(&manager->lock);
/*
* Make sure we only get called once.
*/
INSIST(!manager->exiting);
manager->exiting = ISC_TRUE;
/*
* Post shutdown event(s) to every task (if they haven't already been
* posted).
*/
for (task = HEAD(manager->tasks);
task != NULL;
task = NEXT(task, link)) {
LOCK(&task->lock);
if (task_shutdown(task))
ENQUEUE(manager->ready_tasks, task, ready_link);
UNLOCK(&task->lock);
}
#ifdef ISC_PLATFORM_USETHREADS
/*
* Wake up any sleeping workers. This ensures we get work done if
* there's work left to do, and if there are already no tasks left
* it will cause the workers to see manager->exiting.
*/
BROADCAST(&manager->work_available);
UNLOCK(&manager->lock);
/*
* Wait for all the worker threads to exit.
*/
for (i = 0; i < manager->workers; i++)
(void)isc_thread_join(manager->threads[i], NULL);
#else
/*
* Dispatch the shutdown events.
*/
UNLOCK(&manager->lock);
isc__taskmgr_dispatch();
#endif
manager_free(manager);
*managerp = NULL;
}
#ifndef ISC_PLATFORM_USETHREADS
isc_result_t
isc__taskmgr_dispatch(void) {
isc_taskmgr_t *manager = taskmgr;
if (taskmgr == NULL)
return (ISC_R_NOTFOUND);
dispatch(manager);
return (ISC_R_SUCCESS);
}
#endif