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zfs-builds-mm/zfs-0.8.3/module/spl/spl-taskq.c

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zfs-0.8.3
2020-03-01 19:43:35 +01:00
/*
* Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC.
* Copyright (C) 2007 The Regents of the University of California.
* Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
* Written by Brian Behlendorf <behlendorf1@llnl.gov>.
* UCRL-CODE-235197
*
* This file is part of the SPL, Solaris Porting Layer.
* For details, see <http://zfsonlinux.org/>.
*
* The SPL is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2 of the License, or (at your
* option) any later version.
*
* The SPL is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* for more details.
*
* You should have received a copy of the GNU General Public License along
* with the SPL. If not, see <http://www.gnu.org/licenses/>.
*
* Solaris Porting Layer (SPL) Task Queue Implementation.
*/
#include <sys/timer.h>
#include <sys/taskq.h>
#include <sys/kmem.h>
#include <sys/tsd.h>
int spl_taskq_thread_bind = 0;
module_param(spl_taskq_thread_bind, int, 0644);
MODULE_PARM_DESC(spl_taskq_thread_bind, "Bind taskq thread to CPU by default");
int spl_taskq_thread_dynamic = 1;
module_param(spl_taskq_thread_dynamic, int, 0644);
MODULE_PARM_DESC(spl_taskq_thread_dynamic, "Allow dynamic taskq threads");
int spl_taskq_thread_priority = 1;
module_param(spl_taskq_thread_priority, int, 0644);
MODULE_PARM_DESC(spl_taskq_thread_priority,
"Allow non-default priority for taskq threads");
int spl_taskq_thread_sequential = 4;
module_param(spl_taskq_thread_sequential, int, 0644);
MODULE_PARM_DESC(spl_taskq_thread_sequential,
"Create new taskq threads after N sequential tasks");
/* Global system-wide dynamic task queue available for all consumers */
taskq_t *system_taskq;
EXPORT_SYMBOL(system_taskq);
/* Global dynamic task queue for long delay */
taskq_t *system_delay_taskq;
EXPORT_SYMBOL(system_delay_taskq);
/* Private dedicated taskq for creating new taskq threads on demand. */
static taskq_t *dynamic_taskq;
static taskq_thread_t *taskq_thread_create(taskq_t *);
/* List of all taskqs */
LIST_HEAD(tq_list);
struct rw_semaphore tq_list_sem;
static uint_t taskq_tsd;
static int
task_km_flags(uint_t flags)
{
if (flags & TQ_NOSLEEP)
return (KM_NOSLEEP);
if (flags & TQ_PUSHPAGE)
return (KM_PUSHPAGE);
return (KM_SLEEP);
}
/*
* taskq_find_by_name - Find the largest instance number of a named taskq.
*/
static int
taskq_find_by_name(const char *name)
{
struct list_head *tql = NULL;
taskq_t *tq;
list_for_each_prev(tql, &tq_list) {
tq = list_entry(tql, taskq_t, tq_taskqs);
if (strcmp(name, tq->tq_name) == 0)
return (tq->tq_instance);
}
return (-1);
}
/*
* NOTE: Must be called with tq->tq_lock held, returns a list_t which
* is not attached to the free, work, or pending taskq lists.
*/
static taskq_ent_t *
task_alloc(taskq_t *tq, uint_t flags, unsigned long *irqflags)
{
taskq_ent_t *t;
int count = 0;
ASSERT(tq);
retry:
/* Acquire taskq_ent_t's from free list if available */
if (!list_empty(&tq->tq_free_list) && !(flags & TQ_NEW)) {
t = list_entry(tq->tq_free_list.next, taskq_ent_t, tqent_list);
ASSERT(!(t->tqent_flags & TQENT_FLAG_PREALLOC));
ASSERT(!(t->tqent_flags & TQENT_FLAG_CANCEL));
ASSERT(!timer_pending(&t->tqent_timer));
list_del_init(&t->tqent_list);
return (t);
}
/* Free list is empty and memory allocations are prohibited */
if (flags & TQ_NOALLOC)
return (NULL);
/* Hit maximum taskq_ent_t pool size */
if (tq->tq_nalloc >= tq->tq_maxalloc) {
if (flags & TQ_NOSLEEP)
return (NULL);
/*
* Sleep periodically polling the free list for an available
* taskq_ent_t. Dispatching with TQ_SLEEP should always succeed
* but we cannot block forever waiting for an taskq_ent_t to
* show up in the free list, otherwise a deadlock can happen.
*
* Therefore, we need to allocate a new task even if the number
* of allocated tasks is above tq->tq_maxalloc, but we still
* end up delaying the task allocation by one second, thereby
* throttling the task dispatch rate.
*/
spin_unlock_irqrestore(&tq->tq_lock, *irqflags);
schedule_timeout(HZ / 100);
spin_lock_irqsave_nested(&tq->tq_lock, *irqflags,
tq->tq_lock_class);
if (count < 100) {
count++;
goto retry;
}
}
spin_unlock_irqrestore(&tq->tq_lock, *irqflags);
t = kmem_alloc(sizeof (taskq_ent_t), task_km_flags(flags));
spin_lock_irqsave_nested(&tq->tq_lock, *irqflags, tq->tq_lock_class);
if (t) {
taskq_init_ent(t);
tq->tq_nalloc++;
}
return (t);
}
/*
* NOTE: Must be called with tq->tq_lock held, expects the taskq_ent_t
* to already be removed from the free, work, or pending taskq lists.
*/
static void
task_free(taskq_t *tq, taskq_ent_t *t)
{
ASSERT(tq);
ASSERT(t);
ASSERT(list_empty(&t->tqent_list));
ASSERT(!timer_pending(&t->tqent_timer));
kmem_free(t, sizeof (taskq_ent_t));
tq->tq_nalloc--;
}
/*
* NOTE: Must be called with tq->tq_lock held, either destroys the
* taskq_ent_t if too many exist or moves it to the free list for later use.
*/
static void
task_done(taskq_t *tq, taskq_ent_t *t)
{
ASSERT(tq);
ASSERT(t);
/* Wake tasks blocked in taskq_wait_id() */
wake_up_all(&t->tqent_waitq);
list_del_init(&t->tqent_list);
if (tq->tq_nalloc <= tq->tq_minalloc) {
t->tqent_id = TASKQID_INVALID;
t->tqent_func = NULL;
t->tqent_arg = NULL;
t->tqent_flags = 0;
list_add_tail(&t->tqent_list, &tq->tq_free_list);
} else {
task_free(tq, t);
}
}
/*
* When a delayed task timer expires remove it from the delay list and
* add it to the priority list in order for immediate processing.
*/
static void
task_expire_impl(taskq_ent_t *t)
{
taskq_ent_t *w;
taskq_t *tq = t->tqent_taskq;
struct list_head *l = NULL;
unsigned long flags;
spin_lock_irqsave_nested(&tq->tq_lock, flags, tq->tq_lock_class);
if (t->tqent_flags & TQENT_FLAG_CANCEL) {
ASSERT(list_empty(&t->tqent_list));
spin_unlock_irqrestore(&tq->tq_lock, flags);
return;
}
t->tqent_birth = jiffies;
/*
* The priority list must be maintained in strict task id order
* from lowest to highest for lowest_id to be easily calculable.
*/
list_del(&t->tqent_list);
list_for_each_prev(l, &tq->tq_prio_list) {
w = list_entry(l, taskq_ent_t, tqent_list);
if (w->tqent_id < t->tqent_id) {
list_add(&t->tqent_list, l);
break;
}
}
if (l == &tq->tq_prio_list)
list_add(&t->tqent_list, &tq->tq_prio_list);
spin_unlock_irqrestore(&tq->tq_lock, flags);
wake_up(&tq->tq_work_waitq);
}
static void
task_expire(spl_timer_list_t tl)
{
struct timer_list *tmr = (struct timer_list *)tl;
taskq_ent_t *t = from_timer(t, tmr, tqent_timer);
task_expire_impl(t);
}
/*
* Returns the lowest incomplete taskqid_t. The taskqid_t may
* be queued on the pending list, on the priority list, on the
* delay list, or on the work list currently being handled, but
* it is not 100% complete yet.
*/
static taskqid_t
taskq_lowest_id(taskq_t *tq)
{
taskqid_t lowest_id = tq->tq_next_id;
taskq_ent_t *t;
taskq_thread_t *tqt;
ASSERT(tq);
if (!list_empty(&tq->tq_pend_list)) {
t = list_entry(tq->tq_pend_list.next, taskq_ent_t, tqent_list);
lowest_id = MIN(lowest_id, t->tqent_id);
}
if (!list_empty(&tq->tq_prio_list)) {
t = list_entry(tq->tq_prio_list.next, taskq_ent_t, tqent_list);
lowest_id = MIN(lowest_id, t->tqent_id);
}
if (!list_empty(&tq->tq_delay_list)) {
t = list_entry(tq->tq_delay_list.next, taskq_ent_t, tqent_list);
lowest_id = MIN(lowest_id, t->tqent_id);
}
if (!list_empty(&tq->tq_active_list)) {
tqt = list_entry(tq->tq_active_list.next, taskq_thread_t,
tqt_active_list);
ASSERT(tqt->tqt_id != TASKQID_INVALID);
lowest_id = MIN(lowest_id, tqt->tqt_id);
}
return (lowest_id);
}
/*
* Insert a task into a list keeping the list sorted by increasing taskqid.
*/
static void
taskq_insert_in_order(taskq_t *tq, taskq_thread_t *tqt)
{
taskq_thread_t *w;
struct list_head *l = NULL;
ASSERT(tq);
ASSERT(tqt);
list_for_each_prev(l, &tq->tq_active_list) {
w = list_entry(l, taskq_thread_t, tqt_active_list);
if (w->tqt_id < tqt->tqt_id) {
list_add(&tqt->tqt_active_list, l);
break;
}
}
if (l == &tq->tq_active_list)
list_add(&tqt->tqt_active_list, &tq->tq_active_list);
}
/*
* Find and return a task from the given list if it exists. The list
* must be in lowest to highest task id order.
*/
static taskq_ent_t *
taskq_find_list(taskq_t *tq, struct list_head *lh, taskqid_t id)
{
struct list_head *l = NULL;
taskq_ent_t *t;
list_for_each(l, lh) {
t = list_entry(l, taskq_ent_t, tqent_list);
if (t->tqent_id == id)
return (t);
if (t->tqent_id > id)
break;
}
return (NULL);
}
/*
* Find an already dispatched task given the task id regardless of what
* state it is in. If a task is still pending it will be returned.
* If a task is executing, then -EBUSY will be returned instead.
* If the task has already been run then NULL is returned.
*/
static taskq_ent_t *
taskq_find(taskq_t *tq, taskqid_t id)
{
taskq_thread_t *tqt;
struct list_head *l = NULL;
taskq_ent_t *t;
t = taskq_find_list(tq, &tq->tq_delay_list, id);
if (t)
return (t);
t = taskq_find_list(tq, &tq->tq_prio_list, id);
if (t)
return (t);
t = taskq_find_list(tq, &tq->tq_pend_list, id);
if (t)
return (t);
list_for_each(l, &tq->tq_active_list) {
tqt = list_entry(l, taskq_thread_t, tqt_active_list);
if (tqt->tqt_id == id) {
/*
* Instead of returning tqt_task, we just return a non
* NULL value to prevent misuse, since tqt_task only
* has two valid fields.
*/
return (ERR_PTR(-EBUSY));
}
}
return (NULL);
}
/*
* Theory for the taskq_wait_id(), taskq_wait_outstanding(), and
* taskq_wait() functions below.
*
* Taskq waiting is accomplished by tracking the lowest outstanding task
* id and the next available task id. As tasks are dispatched they are
* added to the tail of the pending, priority, or delay lists. As worker
* threads become available the tasks are removed from the heads of these
* lists and linked to the worker threads. This ensures the lists are
* kept sorted by lowest to highest task id.
*
* Therefore the lowest outstanding task id can be quickly determined by
* checking the head item from all of these lists. This value is stored
* with the taskq as the lowest id. It only needs to be recalculated when
* either the task with the current lowest id completes or is canceled.
*
* By blocking until the lowest task id exceeds the passed task id the
* taskq_wait_outstanding() function can be easily implemented. Similarly,
* by blocking until the lowest task id matches the next task id taskq_wait()
* can be implemented.
*
* Callers should be aware that when there are multiple worked threads it
* is possible for larger task ids to complete before smaller ones. Also
* when the taskq contains delay tasks with small task ids callers may
* block for a considerable length of time waiting for them to expire and
* execute.
*/
static int
taskq_wait_id_check(taskq_t *tq, taskqid_t id)
{
int rc;
unsigned long flags;
spin_lock_irqsave_nested(&tq->tq_lock, flags, tq->tq_lock_class);
rc = (taskq_find(tq, id) == NULL);
spin_unlock_irqrestore(&tq->tq_lock, flags);
return (rc);
}
/*
* The taskq_wait_id() function blocks until the passed task id completes.
* This does not guarantee that all lower task ids have completed.
*/
void
taskq_wait_id(taskq_t *tq, taskqid_t id)
{
wait_event(tq->tq_wait_waitq, taskq_wait_id_check(tq, id));
}
EXPORT_SYMBOL(taskq_wait_id);
static int
taskq_wait_outstanding_check(taskq_t *tq, taskqid_t id)
{
int rc;
unsigned long flags;
spin_lock_irqsave_nested(&tq->tq_lock, flags, tq->tq_lock_class);
rc = (id < tq->tq_lowest_id);
spin_unlock_irqrestore(&tq->tq_lock, flags);
return (rc);
}
/*
* The taskq_wait_outstanding() function will block until all tasks with a
* lower taskqid than the passed 'id' have been completed. Note that all
* task id's are assigned monotonically at dispatch time. Zero may be
* passed for the id to indicate all tasks dispatch up to this point,
* but not after, should be waited for.
*/
void
taskq_wait_outstanding(taskq_t *tq, taskqid_t id)
{
id = id ? id : tq->tq_next_id - 1;
wait_event(tq->tq_wait_waitq, taskq_wait_outstanding_check(tq, id));
}
EXPORT_SYMBOL(taskq_wait_outstanding);
static int
taskq_wait_check(taskq_t *tq)
{
int rc;
unsigned long flags;
spin_lock_irqsave_nested(&tq->tq_lock, flags, tq->tq_lock_class);
rc = (tq->tq_lowest_id == tq->tq_next_id);
spin_unlock_irqrestore(&tq->tq_lock, flags);
return (rc);
}
/*
* The taskq_wait() function will block until the taskq is empty.
* This means that if a taskq re-dispatches work to itself taskq_wait()
* callers will block indefinitely.
*/
void
taskq_wait(taskq_t *tq)
{
wait_event(tq->tq_wait_waitq, taskq_wait_check(tq));
}
EXPORT_SYMBOL(taskq_wait);
int
taskq_member(taskq_t *tq, kthread_t *t)
{
return (tq == (taskq_t *)tsd_get_by_thread(taskq_tsd, t));
}
EXPORT_SYMBOL(taskq_member);
/*
* Cancel an already dispatched task given the task id. Still pending tasks
* will be immediately canceled, and if the task is active the function will
* block until it completes. Preallocated tasks which are canceled must be
* freed by the caller.
*/
int
taskq_cancel_id(taskq_t *tq, taskqid_t id)
{
taskq_ent_t *t;
int rc = ENOENT;
unsigned long flags;
ASSERT(tq);
spin_lock_irqsave_nested(&tq->tq_lock, flags, tq->tq_lock_class);
t = taskq_find(tq, id);
if (t && t != ERR_PTR(-EBUSY)) {
list_del_init(&t->tqent_list);
t->tqent_flags |= TQENT_FLAG_CANCEL;
/*
* When canceling the lowest outstanding task id we
* must recalculate the new lowest outstanding id.
*/
if (tq->tq_lowest_id == t->tqent_id) {
tq->tq_lowest_id = taskq_lowest_id(tq);
ASSERT3S(tq->tq_lowest_id, >, t->tqent_id);
}
/*
* The task_expire() function takes the tq->tq_lock so drop
* drop the lock before synchronously cancelling the timer.
*/
if (timer_pending(&t->tqent_timer)) {
spin_unlock_irqrestore(&tq->tq_lock, flags);
del_timer_sync(&t->tqent_timer);
spin_lock_irqsave_nested(&tq->tq_lock, flags,
tq->tq_lock_class);
}
if (!(t->tqent_flags & TQENT_FLAG_PREALLOC))
task_done(tq, t);
rc = 0;
}
spin_unlock_irqrestore(&tq->tq_lock, flags);
if (t == ERR_PTR(-EBUSY)) {
taskq_wait_id(tq, id);
rc = EBUSY;
}
return (rc);
}
EXPORT_SYMBOL(taskq_cancel_id);
static int taskq_thread_spawn(taskq_t *tq);
taskqid_t
taskq_dispatch(taskq_t *tq, task_func_t func, void *arg, uint_t flags)
{
taskq_ent_t *t;
taskqid_t rc = TASKQID_INVALID;
unsigned long irqflags;
ASSERT(tq);
ASSERT(func);
spin_lock_irqsave_nested(&tq->tq_lock, irqflags, tq->tq_lock_class);
/* Taskq being destroyed and all tasks drained */
if (!(tq->tq_flags & TASKQ_ACTIVE))
goto out;
/* Do not queue the task unless there is idle thread for it */
ASSERT(tq->tq_nactive <= tq->tq_nthreads);
if ((flags & TQ_NOQUEUE) && (tq->tq_nactive == tq->tq_nthreads)) {
/* Dynamic taskq may be able to spawn another thread */
if (!(tq->tq_flags & TASKQ_DYNAMIC) ||
taskq_thread_spawn(tq) == 0)
goto out;
}
if ((t = task_alloc(tq, flags, &irqflags)) == NULL)
goto out;
spin_lock(&t->tqent_lock);
/* Queue to the front of the list to enforce TQ_NOQUEUE semantics */
if (flags & TQ_NOQUEUE)
list_add(&t->tqent_list, &tq->tq_prio_list);
/* Queue to the priority list instead of the pending list */
else if (flags & TQ_FRONT)
list_add_tail(&t->tqent_list, &tq->tq_prio_list);
else
list_add_tail(&t->tqent_list, &tq->tq_pend_list);
t->tqent_id = rc = tq->tq_next_id;
tq->tq_next_id++;
t->tqent_func = func;
t->tqent_arg = arg;
t->tqent_taskq = tq;
t->tqent_timer.function = NULL;
t->tqent_timer.expires = 0;
t->tqent_birth = jiffies;
ASSERT(!(t->tqent_flags & TQENT_FLAG_PREALLOC));
spin_unlock(&t->tqent_lock);
wake_up(&tq->tq_work_waitq);
out:
/* Spawn additional taskq threads if required. */
if (!(flags & TQ_NOQUEUE) && tq->tq_nactive == tq->tq_nthreads)
(void) taskq_thread_spawn(tq);
spin_unlock_irqrestore(&tq->tq_lock, irqflags);
return (rc);
}
EXPORT_SYMBOL(taskq_dispatch);
taskqid_t
taskq_dispatch_delay(taskq_t *tq, task_func_t func, void *arg,
uint_t flags, clock_t expire_time)
{
taskqid_t rc = TASKQID_INVALID;
taskq_ent_t *t;
unsigned long irqflags;
ASSERT(tq);
ASSERT(func);
spin_lock_irqsave_nested(&tq->tq_lock, irqflags, tq->tq_lock_class);
/* Taskq being destroyed and all tasks drained */
if (!(tq->tq_flags & TASKQ_ACTIVE))
goto out;
if ((t = task_alloc(tq, flags, &irqflags)) == NULL)
goto out;
spin_lock(&t->tqent_lock);
/* Queue to the delay list for subsequent execution */
list_add_tail(&t->tqent_list, &tq->tq_delay_list);
t->tqent_id = rc = tq->tq_next_id;
tq->tq_next_id++;
t->tqent_func = func;
t->tqent_arg = arg;
t->tqent_taskq = tq;
t->tqent_timer.function = task_expire;
t->tqent_timer.expires = (unsigned long)expire_time;
add_timer(&t->tqent_timer);
ASSERT(!(t->tqent_flags & TQENT_FLAG_PREALLOC));
spin_unlock(&t->tqent_lock);
out:
/* Spawn additional taskq threads if required. */
if (tq->tq_nactive == tq->tq_nthreads)
(void) taskq_thread_spawn(tq);
spin_unlock_irqrestore(&tq->tq_lock, irqflags);
return (rc);
}
EXPORT_SYMBOL(taskq_dispatch_delay);
void
taskq_dispatch_ent(taskq_t *tq, task_func_t func, void *arg, uint_t flags,
taskq_ent_t *t)
{
unsigned long irqflags;
ASSERT(tq);
ASSERT(func);
spin_lock_irqsave_nested(&tq->tq_lock, irqflags,
tq->tq_lock_class);
/* Taskq being destroyed and all tasks drained */
if (!(tq->tq_flags & TASKQ_ACTIVE)) {
t->tqent_id = TASKQID_INVALID;
goto out;
}
if ((flags & TQ_NOQUEUE) && (tq->tq_nactive == tq->tq_nthreads)) {
/* Dynamic taskq may be able to spawn another thread */
if (!(tq->tq_flags & TASKQ_DYNAMIC) ||
taskq_thread_spawn(tq) == 0)
goto out2;
flags |= TQ_FRONT;
}
spin_lock(&t->tqent_lock);
/*
* Make sure the entry is not on some other taskq; it is important to
* ASSERT() under lock
*/
ASSERT(taskq_empty_ent(t));
/*
* Mark it as a prealloc'd task. This is important
* to ensure that we don't free it later.
*/
t->tqent_flags |= TQENT_FLAG_PREALLOC;
/* Queue to the priority list instead of the pending list */
if (flags & TQ_FRONT)
list_add_tail(&t->tqent_list, &tq->tq_prio_list);
else
list_add_tail(&t->tqent_list, &tq->tq_pend_list);
t->tqent_id = tq->tq_next_id;
tq->tq_next_id++;
t->tqent_func = func;
t->tqent_arg = arg;
t->tqent_taskq = tq;
t->tqent_birth = jiffies;
spin_unlock(&t->tqent_lock);
wake_up(&tq->tq_work_waitq);
out:
/* Spawn additional taskq threads if required. */
if (tq->tq_nactive == tq->tq_nthreads)
(void) taskq_thread_spawn(tq);
out2:
spin_unlock_irqrestore(&tq->tq_lock, irqflags);
}
EXPORT_SYMBOL(taskq_dispatch_ent);
int
taskq_empty_ent(taskq_ent_t *t)
{
return (list_empty(&t->tqent_list));
}
EXPORT_SYMBOL(taskq_empty_ent);
void
taskq_init_ent(taskq_ent_t *t)
{
spin_lock_init(&t->tqent_lock);
init_waitqueue_head(&t->tqent_waitq);
timer_setup(&t->tqent_timer, NULL, 0);
INIT_LIST_HEAD(&t->tqent_list);
t->tqent_id = 0;
t->tqent_func = NULL;
t->tqent_arg = NULL;
t->tqent_flags = 0;
t->tqent_taskq = NULL;
}
EXPORT_SYMBOL(taskq_init_ent);
/*
* Return the next pending task, preference is given to tasks on the
* priority list which were dispatched with TQ_FRONT.
*/
static taskq_ent_t *
taskq_next_ent(taskq_t *tq)
{
struct list_head *list;
if (!list_empty(&tq->tq_prio_list))
list = &tq->tq_prio_list;
else if (!list_empty(&tq->tq_pend_list))
list = &tq->tq_pend_list;
else
return (NULL);
return (list_entry(list->next, taskq_ent_t, tqent_list));
}
/*
* Spawns a new thread for the specified taskq.
*/
static void
taskq_thread_spawn_task(void *arg)
{
taskq_t *tq = (taskq_t *)arg;
unsigned long flags;
if (taskq_thread_create(tq) == NULL) {
/* restore spawning count if failed */
spin_lock_irqsave_nested(&tq->tq_lock, flags,
tq->tq_lock_class);
tq->tq_nspawn--;
spin_unlock_irqrestore(&tq->tq_lock, flags);
}
}
/*
* Spawn addition threads for dynamic taskqs (TASKQ_DYNAMIC) the current
* number of threads is insufficient to handle the pending tasks. These
* new threads must be created by the dedicated dynamic_taskq to avoid
* deadlocks between thread creation and memory reclaim. The system_taskq
* which is also a dynamic taskq cannot be safely used for this.
*/
static int
taskq_thread_spawn(taskq_t *tq)
{
int spawning = 0;
if (!(tq->tq_flags & TASKQ_DYNAMIC))
return (0);
if ((tq->tq_nthreads + tq->tq_nspawn < tq->tq_maxthreads) &&
(tq->tq_flags & TASKQ_ACTIVE)) {
spawning = (++tq->tq_nspawn);
taskq_dispatch(dynamic_taskq, taskq_thread_spawn_task,
tq, TQ_NOSLEEP);
}
return (spawning);
}
/*
* Threads in a dynamic taskq should only exit once it has been completely
* drained and no other threads are actively servicing tasks. This prevents
* threads from being created and destroyed more than is required.
*
* The first thread is the thread list is treated as the primary thread.
* There is nothing special about the primary thread but in order to avoid
* all the taskq pids from changing we opt to make it long running.
*/
static int
taskq_thread_should_stop(taskq_t *tq, taskq_thread_t *tqt)
{
if (!(tq->tq_flags & TASKQ_DYNAMIC))
return (0);
if (list_first_entry(&(tq->tq_thread_list), taskq_thread_t,
tqt_thread_list) == tqt)
return (0);
return
((tq->tq_nspawn == 0) && /* No threads are being spawned */
(tq->tq_nactive == 0) && /* No threads are handling tasks */
(tq->tq_nthreads > 1) && /* More than 1 thread is running */
(!taskq_next_ent(tq)) && /* There are no pending tasks */
(spl_taskq_thread_dynamic)); /* Dynamic taskqs are allowed */
}
static int
taskq_thread(void *args)
{
DECLARE_WAITQUEUE(wait, current);
sigset_t blocked;
taskq_thread_t *tqt = args;
taskq_t *tq;
taskq_ent_t *t;
int seq_tasks = 0;
unsigned long flags;
taskq_ent_t dup_task = {};
ASSERT(tqt);
ASSERT(tqt->tqt_tq);
tq = tqt->tqt_tq;
current->flags |= PF_NOFREEZE;
(void) spl_fstrans_mark();
sigfillset(&blocked);
sigprocmask(SIG_BLOCK, &blocked, NULL);
flush_signals(current);
tsd_set(taskq_tsd, tq);
spin_lock_irqsave_nested(&tq->tq_lock, flags, tq->tq_lock_class);
/*
* If we are dynamically spawned, decrease spawning count. Note that
* we could be created during taskq_create, in which case we shouldn't
* do the decrement. But it's fine because taskq_create will reset
* tq_nspawn later.
*/
if (tq->tq_flags & TASKQ_DYNAMIC)
tq->tq_nspawn--;
/* Immediately exit if more threads than allowed were created. */
if (tq->tq_nthreads >= tq->tq_maxthreads)
goto error;
tq->tq_nthreads++;
list_add_tail(&tqt->tqt_thread_list, &tq->tq_thread_list);
wake_up(&tq->tq_wait_waitq);
set_current_state(TASK_INTERRUPTIBLE);
while (!kthread_should_stop()) {
if (list_empty(&tq->tq_pend_list) &&
list_empty(&tq->tq_prio_list)) {
if (taskq_thread_should_stop(tq, tqt)) {
wake_up_all(&tq->tq_wait_waitq);
break;
}
add_wait_queue_exclusive(&tq->tq_work_waitq, &wait);
spin_unlock_irqrestore(&tq->tq_lock, flags);
schedule();
seq_tasks = 0;
spin_lock_irqsave_nested(&tq->tq_lock, flags,
tq->tq_lock_class);
remove_wait_queue(&tq->tq_work_waitq, &wait);
} else {
__set_current_state(TASK_RUNNING);
}
if ((t = taskq_next_ent(tq)) != NULL) {
list_del_init(&t->tqent_list);
/*
* A TQENT_FLAG_PREALLOC task may be reused or freed
* during the task function call. Store tqent_id and
* tqent_flags here.
*
* Also use an on stack taskq_ent_t for tqt_task
* assignment in this case. We only populate the two
* fields used by the only user in taskq proc file.
*/
tqt->tqt_id = t->tqent_id;
tqt->tqt_flags = t->tqent_flags;
if (t->tqent_flags & TQENT_FLAG_PREALLOC) {
dup_task.tqent_func = t->tqent_func;
dup_task.tqent_arg = t->tqent_arg;
t = &dup_task;
}
tqt->tqt_task = t;
taskq_insert_in_order(tq, tqt);
tq->tq_nactive++;
spin_unlock_irqrestore(&tq->tq_lock, flags);
/* Perform the requested task */
t->tqent_func(t->tqent_arg);
spin_lock_irqsave_nested(&tq->tq_lock, flags,
tq->tq_lock_class);
tq->tq_nactive--;
list_del_init(&tqt->tqt_active_list);
tqt->tqt_task = NULL;
/* For prealloc'd tasks, we don't free anything. */
if (!(tqt->tqt_flags & TQENT_FLAG_PREALLOC))
task_done(tq, t);
/*
* When the current lowest outstanding taskqid is
* done calculate the new lowest outstanding id
*/
if (tq->tq_lowest_id == tqt->tqt_id) {
tq->tq_lowest_id = taskq_lowest_id(tq);
ASSERT3S(tq->tq_lowest_id, >, tqt->tqt_id);
}
/* Spawn additional taskq threads if required. */
if ((++seq_tasks) > spl_taskq_thread_sequential &&
taskq_thread_spawn(tq))
seq_tasks = 0;
tqt->tqt_id = TASKQID_INVALID;
tqt->tqt_flags = 0;
wake_up_all(&tq->tq_wait_waitq);
} else {
if (taskq_thread_should_stop(tq, tqt))
break;
}
set_current_state(TASK_INTERRUPTIBLE);
}
__set_current_state(TASK_RUNNING);
tq->tq_nthreads--;
list_del_init(&tqt->tqt_thread_list);
error:
kmem_free(tqt, sizeof (taskq_thread_t));
spin_unlock_irqrestore(&tq->tq_lock, flags);
tsd_set(taskq_tsd, NULL);
return (0);
}
static taskq_thread_t *
taskq_thread_create(taskq_t *tq)
{
static int last_used_cpu = 0;
taskq_thread_t *tqt;
tqt = kmem_alloc(sizeof (*tqt), KM_PUSHPAGE);
INIT_LIST_HEAD(&tqt->tqt_thread_list);
INIT_LIST_HEAD(&tqt->tqt_active_list);
tqt->tqt_tq = tq;
tqt->tqt_id = TASKQID_INVALID;
tqt->tqt_thread = spl_kthread_create(taskq_thread, tqt,
"%s", tq->tq_name);
if (tqt->tqt_thread == NULL) {
kmem_free(tqt, sizeof (taskq_thread_t));
return (NULL);
}
if (spl_taskq_thread_bind) {
last_used_cpu = (last_used_cpu + 1) % num_online_cpus();
kthread_bind(tqt->tqt_thread, last_used_cpu);
}
if (spl_taskq_thread_priority)
set_user_nice(tqt->tqt_thread, PRIO_TO_NICE(tq->tq_pri));
wake_up_process(tqt->tqt_thread);
return (tqt);
}
taskq_t *
taskq_create(const char *name, int nthreads, pri_t pri,
int minalloc, int maxalloc, uint_t flags)
{
taskq_t *tq;
taskq_thread_t *tqt;
int count = 0, rc = 0, i;
unsigned long irqflags;
ASSERT(name != NULL);
ASSERT(minalloc >= 0);
ASSERT(maxalloc <= INT_MAX);
ASSERT(!(flags & (TASKQ_CPR_SAFE))); /* Unsupported */
/* Scale the number of threads using nthreads as a percentage */
if (flags & TASKQ_THREADS_CPU_PCT) {
ASSERT(nthreads <= 100);
ASSERT(nthreads >= 0);
nthreads = MIN(nthreads, 100);
nthreads = MAX(nthreads, 0);
nthreads = MAX((num_online_cpus() * nthreads) / 100, 1);
}
tq = kmem_alloc(sizeof (*tq), KM_PUSHPAGE);
if (tq == NULL)
return (NULL);
spin_lock_init(&tq->tq_lock);
INIT_LIST_HEAD(&tq->tq_thread_list);
INIT_LIST_HEAD(&tq->tq_active_list);
tq->tq_name = strdup(name);
tq->tq_nactive = 0;
tq->tq_nthreads = 0;
tq->tq_nspawn = 0;
tq->tq_maxthreads = nthreads;
tq->tq_pri = pri;
tq->tq_minalloc = minalloc;
tq->tq_maxalloc = maxalloc;
tq->tq_nalloc = 0;
tq->tq_flags = (flags | TASKQ_ACTIVE);
tq->tq_next_id = TASKQID_INITIAL;
tq->tq_lowest_id = TASKQID_INITIAL;
INIT_LIST_HEAD(&tq->tq_free_list);
INIT_LIST_HEAD(&tq->tq_pend_list);
INIT_LIST_HEAD(&tq->tq_prio_list);
INIT_LIST_HEAD(&tq->tq_delay_list);
init_waitqueue_head(&tq->tq_work_waitq);
init_waitqueue_head(&tq->tq_wait_waitq);
tq->tq_lock_class = TQ_LOCK_GENERAL;
INIT_LIST_HEAD(&tq->tq_taskqs);
if (flags & TASKQ_PREPOPULATE) {
spin_lock_irqsave_nested(&tq->tq_lock, irqflags,
tq->tq_lock_class);
for (i = 0; i < minalloc; i++)
task_done(tq, task_alloc(tq, TQ_PUSHPAGE | TQ_NEW,
&irqflags));
spin_unlock_irqrestore(&tq->tq_lock, irqflags);
}
if ((flags & TASKQ_DYNAMIC) && spl_taskq_thread_dynamic)
nthreads = 1;
for (i = 0; i < nthreads; i++) {
tqt = taskq_thread_create(tq);
if (tqt == NULL)
rc = 1;
else
count++;
}
/* Wait for all threads to be started before potential destroy */
wait_event(tq->tq_wait_waitq, tq->tq_nthreads == count);
/*
* taskq_thread might have touched nspawn, but we don't want them to
* because they're not dynamically spawned. So we reset it to 0
*/
tq->tq_nspawn = 0;
if (rc) {
taskq_destroy(tq);
tq = NULL;
} else {
down_write(&tq_list_sem);
tq->tq_instance = taskq_find_by_name(name) + 1;
list_add_tail(&tq->tq_taskqs, &tq_list);
up_write(&tq_list_sem);
}
return (tq);
}
EXPORT_SYMBOL(taskq_create);
void
taskq_destroy(taskq_t *tq)
{
struct task_struct *thread;
taskq_thread_t *tqt;
taskq_ent_t *t;
unsigned long flags;
ASSERT(tq);
spin_lock_irqsave_nested(&tq->tq_lock, flags, tq->tq_lock_class);
tq->tq_flags &= ~TASKQ_ACTIVE;
spin_unlock_irqrestore(&tq->tq_lock, flags);
/*
* When TASKQ_ACTIVE is clear new tasks may not be added nor may
* new worker threads be spawned for dynamic taskq.
*/
if (dynamic_taskq != NULL)
taskq_wait_outstanding(dynamic_taskq, 0);
taskq_wait(tq);
/* remove taskq from global list used by the kstats */
down_write(&tq_list_sem);
list_del(&tq->tq_taskqs);
up_write(&tq_list_sem);
spin_lock_irqsave_nested(&tq->tq_lock, flags, tq->tq_lock_class);
/* wait for spawning threads to insert themselves to the list */
while (tq->tq_nspawn) {
spin_unlock_irqrestore(&tq->tq_lock, flags);
schedule_timeout_interruptible(1);
spin_lock_irqsave_nested(&tq->tq_lock, flags,
tq->tq_lock_class);
}
/*
* Signal each thread to exit and block until it does. Each thread
* is responsible for removing itself from the list and freeing its
* taskq_thread_t. This allows for idle threads to opt to remove
* themselves from the taskq. They can be recreated as needed.
*/
while (!list_empty(&tq->tq_thread_list)) {
tqt = list_entry(tq->tq_thread_list.next,
taskq_thread_t, tqt_thread_list);
thread = tqt->tqt_thread;
spin_unlock_irqrestore(&tq->tq_lock, flags);
kthread_stop(thread);
spin_lock_irqsave_nested(&tq->tq_lock, flags,
tq->tq_lock_class);
}
while (!list_empty(&tq->tq_free_list)) {
t = list_entry(tq->tq_free_list.next, taskq_ent_t, tqent_list);
ASSERT(!(t->tqent_flags & TQENT_FLAG_PREALLOC));
list_del_init(&t->tqent_list);
task_free(tq, t);
}
ASSERT0(tq->tq_nthreads);
ASSERT0(tq->tq_nalloc);
ASSERT0(tq->tq_nspawn);
ASSERT(list_empty(&tq->tq_thread_list));
ASSERT(list_empty(&tq->tq_active_list));
ASSERT(list_empty(&tq->tq_free_list));
ASSERT(list_empty(&tq->tq_pend_list));
ASSERT(list_empty(&tq->tq_prio_list));
ASSERT(list_empty(&tq->tq_delay_list));
spin_unlock_irqrestore(&tq->tq_lock, flags);
strfree(tq->tq_name);
kmem_free(tq, sizeof (taskq_t));
}
EXPORT_SYMBOL(taskq_destroy);
static unsigned int spl_taskq_kick = 0;
/*
* 2.6.36 API Change
* module_param_cb is introduced to take kernel_param_ops and
* module_param_call is marked as obsolete. Also set and get operations
* were changed to take a 'const struct kernel_param *'.
*/
static int
#ifdef module_param_cb
param_set_taskq_kick(const char *val, const struct kernel_param *kp)
#else
param_set_taskq_kick(const char *val, struct kernel_param *kp)
#endif
{
int ret;
taskq_t *tq = NULL;
taskq_ent_t *t;
unsigned long flags;
ret = param_set_uint(val, kp);
if (ret < 0 || !spl_taskq_kick)
return (ret);
/* reset value */
spl_taskq_kick = 0;
down_read(&tq_list_sem);
list_for_each_entry(tq, &tq_list, tq_taskqs) {
spin_lock_irqsave_nested(&tq->tq_lock, flags,
tq->tq_lock_class);
/* Check if the first pending is older than 5 seconds */
t = taskq_next_ent(tq);
if (t && time_after(jiffies, t->tqent_birth + 5*HZ)) {
(void) taskq_thread_spawn(tq);
printk(KERN_INFO "spl: Kicked taskq %s/%d\n",
tq->tq_name, tq->tq_instance);
}
spin_unlock_irqrestore(&tq->tq_lock, flags);
}
up_read(&tq_list_sem);
return (ret);
}
#ifdef module_param_cb
static const struct kernel_param_ops param_ops_taskq_kick = {
.set = param_set_taskq_kick,
.get = param_get_uint,
};
module_param_cb(spl_taskq_kick, &param_ops_taskq_kick, &spl_taskq_kick, 0644);
#else
module_param_call(spl_taskq_kick, param_set_taskq_kick, param_get_uint,
&spl_taskq_kick, 0644);
#endif
MODULE_PARM_DESC(spl_taskq_kick,
"Write nonzero to kick stuck taskqs to spawn more threads");
int
spl_taskq_init(void)
{
init_rwsem(&tq_list_sem);
tsd_create(&taskq_tsd, NULL);
system_taskq = taskq_create("spl_system_taskq", MAX(boot_ncpus, 64),
maxclsyspri, boot_ncpus, INT_MAX, TASKQ_PREPOPULATE|TASKQ_DYNAMIC);
if (system_taskq == NULL)
return (1);
system_delay_taskq = taskq_create("spl_delay_taskq", MAX(boot_ncpus, 4),
maxclsyspri, boot_ncpus, INT_MAX, TASKQ_PREPOPULATE|TASKQ_DYNAMIC);
if (system_delay_taskq == NULL) {
taskq_destroy(system_taskq);
return (1);
}
dynamic_taskq = taskq_create("spl_dynamic_taskq", 1,
maxclsyspri, boot_ncpus, INT_MAX, TASKQ_PREPOPULATE);
if (dynamic_taskq == NULL) {
taskq_destroy(system_taskq);
taskq_destroy(system_delay_taskq);
return (1);
}
/*
* This is used to annotate tq_lock, so
* taskq_dispatch -> taskq_thread_spawn -> taskq_dispatch
* does not trigger a lockdep warning re: possible recursive locking
*/
dynamic_taskq->tq_lock_class = TQ_LOCK_DYNAMIC;
return (0);
}
void
spl_taskq_fini(void)
{
taskq_destroy(dynamic_taskq);
dynamic_taskq = NULL;
taskq_destroy(system_delay_taskq);
system_delay_taskq = NULL;
taskq_destroy(system_taskq);
system_taskq = NULL;
tsd_destroy(&taskq_tsd);
}
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