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zfs/module/spl/spl-taskq.c

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/*****************************************************************************\
* 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://github.com/behlendorf/spl/>.
*
* 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/taskq.h>
#include <sys/kmem.h>
#include <spl-debug.h>
#ifdef SS_DEBUG_SUBSYS
#undef SS_DEBUG_SUBSYS
#endif
#define SS_DEBUG_SUBSYS SS_TASKQ
/* Global system-wide dynamic task queue available for all consumers */
taskq_t *system_taskq;
EXPORT_SYMBOL(system_taskq);
typedef struct spl_task {
spinlock_t t_lock;
struct list_head t_list;
taskqid_t t_id;
task_func_t *t_func;
void *t_arg;
} spl_task_t;
/*
* 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 spl_task_t *
task_alloc(taskq_t *tq, uint_t flags)
{
spl_task_t *t;
int count = 0;
SENTRY;
ASSERT(tq);
ASSERT(flags & (TQ_SLEEP | TQ_NOSLEEP)); /* One set */
ASSERT(!((flags & TQ_SLEEP) && (flags & TQ_NOSLEEP))); /* Not both */
ASSERT(spin_is_locked(&tq->tq_lock));
retry:
/* Acquire spl_task_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, spl_task_t, t_list);
list_del_init(&t->t_list);
SRETURN(t);
}
/* Free list is empty and memory allocations are prohibited */
if (flags & TQ_NOALLOC)
SRETURN(NULL);
/* Hit maximum spl_task_t pool size */
if (tq->tq_nalloc >= tq->tq_maxalloc) {
if (flags & TQ_NOSLEEP)
SRETURN(NULL);
/*
* Sleep periodically polling the free list for an available
* spl_task_t. Dispatching with TQ_SLEEP should always succeed
* but we cannot block forever waiting for an spl_taskq_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, tq->tq_lock_flags);
schedule_timeout(HZ / 100);
spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags);
if (count < 100)
SGOTO(retry, count++);
}
spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags);
t = kmem_alloc(sizeof(spl_task_t), flags & (TQ_SLEEP | TQ_NOSLEEP));
spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags);
if (t) {
spin_lock_init(&t->t_lock);
INIT_LIST_HEAD(&t->t_list);
t->t_id = 0;
t->t_func = NULL;
t->t_arg = NULL;
tq->tq_nalloc++;
}
SRETURN(t);
}
/*
* NOTE: Must be called with tq->tq_lock held, expects the spl_task_t
* to already be removed from the free, work, or pending taskq lists.
*/
static void
task_free(taskq_t *tq, spl_task_t *t)
{
SENTRY;
ASSERT(tq);
ASSERT(t);
ASSERT(spin_is_locked(&tq->tq_lock));
ASSERT(list_empty(&t->t_list));
kmem_free(t, sizeof(spl_task_t));
tq->tq_nalloc--;
SEXIT;
}
/*
* NOTE: Must be called with tq->tq_lock held, either destroys the
* spl_task_t if too many exist or moves it to the free list for later use.
*/
static void
task_done(taskq_t *tq, spl_task_t *t)
{
SENTRY;
ASSERT(tq);
ASSERT(t);
ASSERT(spin_is_locked(&tq->tq_lock));
list_del_init(&t->t_list);
if (tq->tq_nalloc <= tq->tq_minalloc) {
t->t_id = 0;
t->t_func = NULL;
t->t_arg = NULL;
list_add_tail(&t->t_list, &tq->tq_free_list);
} else {
task_free(tq, t);
}
SEXIT;
}
/*
* As tasks are submitted to the task queue they are assigned a
* monotonically increasing taskqid and added to the tail of the pending
* list. As worker threads become available the tasks are removed from
* the head of the pending or priority list, giving preference to the
* priority list. The tasks are then added to the work list, preserving
* the ordering by taskqid. Finally, as tasks complete they are removed
* from the work list. This means that the pending and work lists are
* always kept sorted by taskqid. Thus the lowest outstanding
* incomplete taskqid can be determined simply by checking the min
* taskqid for each head item on the pending, priority, and work list.
* This value is stored in tq->tq_lowest_id and only updated to the new
* lowest id when the previous lowest id completes. All taskqids lower
* than tq->tq_lowest_id must have completed. It is also possible
* larger taskqid's have completed because they may be processed in
* parallel by several worker threads. However, this is not a problem
* because the behavior of taskq_wait_id() is to block until all
* previously submitted taskqid's have completed.
*
* XXX: Taskqid_t wrapping is not handled. However, taskqid_t's are
* 64-bit values so even if a taskq is processing 2^24 (16,777,216)
* taskqid_ts per second it will still take 2^40 seconds, 34,865 years,
* before the wrap occurs. I can live with that for now.
*/
static int
taskq_wait_check(taskq_t *tq, taskqid_t id)
{
int rc;
spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags);
rc = (id < tq->tq_lowest_id);
spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags);
SRETURN(rc);
}
void
__taskq_wait_id(taskq_t *tq, taskqid_t id)
{
SENTRY;
ASSERT(tq);
wait_event(tq->tq_wait_waitq, taskq_wait_check(tq, id));
SEXIT;
}
EXPORT_SYMBOL(__taskq_wait_id);
void
__taskq_wait(taskq_t *tq)
{
taskqid_t id;
SENTRY;
ASSERT(tq);
/* Wait for the largest outstanding taskqid */
spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags);
id = tq->tq_next_id - 1;
spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags);
__taskq_wait_id(tq, id);
SEXIT;
}
EXPORT_SYMBOL(__taskq_wait);
int
__taskq_member(taskq_t *tq, void *t)
{
int i;
SENTRY;
ASSERT(tq);
ASSERT(t);
for (i = 0; i < tq->tq_nthreads; i++)
if (tq->tq_threads[i] == (struct task_struct *)t)
SRETURN(1);
SRETURN(0);
}
EXPORT_SYMBOL(__taskq_member);
taskqid_t
__taskq_dispatch(taskq_t *tq, task_func_t func, void *arg, uint_t flags)
{
spl_task_t *t;
taskqid_t rc = 0;
SENTRY;
ASSERT(tq);
ASSERT(func);
/* Solaris assumes TQ_SLEEP if not passed explicitly */
if (!(flags & (TQ_SLEEP | TQ_NOSLEEP)))
flags |= TQ_SLEEP;
if (unlikely(in_atomic() && (flags & TQ_SLEEP)))
PANIC("May schedule while atomic: %s/0x%08x/%d\n",
current->comm, preempt_count(), current->pid);
spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags);
/* Taskq being destroyed and all tasks drained */
if (!(tq->tq_flags & TQ_ACTIVE))
SGOTO(out, rc = 0);
/* 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))
SGOTO(out, rc = 0);
if ((t = task_alloc(tq, flags)) == NULL)
SGOTO(out, rc = 0);
spin_lock(&t->t_lock);
/* Queue to the priority list instead of the pending list */
if (flags & TQ_FRONT)
list_add_tail(&t->t_list, &tq->tq_prio_list);
else
list_add_tail(&t->t_list, &tq->tq_pend_list);
t->t_id = rc = tq->tq_next_id;
tq->tq_next_id++;
t->t_func = func;
t->t_arg = arg;
spin_unlock(&t->t_lock);
wake_up(&tq->tq_work_waitq);
out:
spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags);
SRETURN(rc);
}
EXPORT_SYMBOL(__taskq_dispatch);
/*
* Returns the lowest incomplete taskqid_t. The taskqid_t may
* be queued on the pending list, on the priority 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;
spl_task_t *t;
SENTRY;
ASSERT(tq);
ASSERT(spin_is_locked(&tq->tq_lock));
if (!list_empty(&tq->tq_pend_list)) {
t = list_entry(tq->tq_pend_list.next, spl_task_t, t_list);
lowest_id = MIN(lowest_id, t->t_id);
}
if (!list_empty(&tq->tq_prio_list)) {
t = list_entry(tq->tq_prio_list.next, spl_task_t, t_list);
lowest_id = MIN(lowest_id, t->t_id);
}
if (!list_empty(&tq->tq_work_list)) {
t = list_entry(tq->tq_work_list.next, spl_task_t, t_list);
lowest_id = MIN(lowest_id, t->t_id);
}
SRETURN(lowest_id);
}
/*
* Insert a task into a list keeping the list sorted by increasing
* taskqid.
*/
static void
taskq_insert_in_order(taskq_t *tq, spl_task_t *t)
{
spl_task_t *w;
struct list_head *l;
SENTRY;
ASSERT(tq);
ASSERT(t);
ASSERT(spin_is_locked(&tq->tq_lock));
list_for_each_prev(l, &tq->tq_work_list) {
w = list_entry(l, spl_task_t, t_list);
if (w->t_id < t->t_id) {
list_add(&t->t_list, l);
break;
}
}
if (l == &tq->tq_work_list)
list_add(&t->t_list, &tq->tq_work_list);
SEXIT;
}
static int
taskq_thread(void *args)
{
DECLARE_WAITQUEUE(wait, current);
sigset_t blocked;
taskqid_t id;
taskq_t *tq = args;
spl_task_t *t;
struct list_head *pend_list;
SENTRY;
ASSERT(tq);
current->flags |= PF_NOFREEZE;
sigfillset(&blocked);
sigprocmask(SIG_BLOCK, &blocked, NULL);
flush_signals(current);
spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags);
tq->tq_nthreads++;
wake_up(&tq->tq_wait_waitq);
set_current_state(TASK_INTERRUPTIBLE);
while (!kthread_should_stop()) {
add_wait_queue(&tq->tq_work_waitq, &wait);
if (list_empty(&tq->tq_pend_list) &&
list_empty(&tq->tq_prio_list)) {
spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags);
schedule();
spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags);
} else {
__set_current_state(TASK_RUNNING);
}
remove_wait_queue(&tq->tq_work_waitq, &wait);
if (!list_empty(&tq->tq_prio_list))
pend_list = &tq->tq_prio_list;
else if (!list_empty(&tq->tq_pend_list))
pend_list = &tq->tq_pend_list;
else
pend_list = NULL;
if (pend_list) {
t = list_entry(pend_list->next, spl_task_t, t_list);
list_del_init(&t->t_list);
taskq_insert_in_order(tq, t);
tq->tq_nactive++;
spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags);
/* Perform the requested task */
t->t_func(t->t_arg);
spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags);
tq->tq_nactive--;
id = t->t_id;
task_done(tq, t);
/* When the current lowest outstanding taskqid is
* done calculate the new lowest outstanding id */
if (tq->tq_lowest_id == id) {
tq->tq_lowest_id = taskq_lowest_id(tq);
ASSERT(tq->tq_lowest_id > id);
}
wake_up_all(&tq->tq_wait_waitq);
}
set_current_state(TASK_INTERRUPTIBLE);
}
__set_current_state(TASK_RUNNING);
tq->tq_nthreads--;
spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags);
SRETURN(0);
}
taskq_t *
__taskq_create(const char *name, int nthreads, pri_t pri,
int minalloc, int maxalloc, uint_t flags)
{
taskq_t *tq;
struct task_struct *t;
int rc = 0, i, j = 0;
SENTRY;
ASSERT(name != NULL);
ASSERT(pri <= maxclsyspri);
ASSERT(minalloc >= 0);
ASSERT(maxalloc <= INT_MAX);
ASSERT(!(flags & (TASKQ_CPR_SAFE | TASKQ_DYNAMIC))); /* 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_SLEEP);
if (tq == NULL)
SRETURN(NULL);
tq->tq_threads = kmem_alloc(nthreads * sizeof(t), KM_SLEEP);
if (tq->tq_threads == NULL) {
kmem_free(tq, sizeof(*tq));
SRETURN(NULL);
}
spin_lock_init(&tq->tq_lock);
spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags);
tq->tq_name = name;
tq->tq_nactive = 0;
tq->tq_nthreads = 0;
tq->tq_pri = pri;
tq->tq_minalloc = minalloc;
tq->tq_maxalloc = maxalloc;
tq->tq_nalloc = 0;
tq->tq_flags = (flags | TQ_ACTIVE);
tq->tq_next_id = 1;
tq->tq_lowest_id = 1;
INIT_LIST_HEAD(&tq->tq_free_list);
INIT_LIST_HEAD(&tq->tq_work_list);
INIT_LIST_HEAD(&tq->tq_pend_list);
INIT_LIST_HEAD(&tq->tq_prio_list);
init_waitqueue_head(&tq->tq_work_waitq);
init_waitqueue_head(&tq->tq_wait_waitq);
if (flags & TASKQ_PREPOPULATE)
for (i = 0; i < minalloc; i++)
task_done(tq, task_alloc(tq, TQ_SLEEP | TQ_NEW));
spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags);
for (i = 0; i < nthreads; i++) {
t = kthread_create(taskq_thread, tq, "%s/%d", name, i);
if (t) {
tq->tq_threads[i] = t;
kthread_bind(t, i % num_online_cpus());
set_user_nice(t, PRIO_TO_NICE(pri));
wake_up_process(t);
j++;
} else {
tq->tq_threads[i] = NULL;
rc = 1;
}
}
/* Wait for all threads to be started before potential destroy */
wait_event(tq->tq_wait_waitq, tq->tq_nthreads == j);
if (rc) {
__taskq_destroy(tq);
tq = NULL;
}
SRETURN(tq);
}
EXPORT_SYMBOL(__taskq_create);
void
__taskq_destroy(taskq_t *tq)
{
spl_task_t *t;
int i, nthreads;
SENTRY;
ASSERT(tq);
spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags);
tq->tq_flags &= ~TQ_ACTIVE;
spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags);
/* TQ_ACTIVE cleared prevents new tasks being added to pending */
__taskq_wait(tq);
nthreads = tq->tq_nthreads;
for (i = 0; i < nthreads; i++)
if (tq->tq_threads[i])
kthread_stop(tq->tq_threads[i]);
spin_lock_irqsave(&tq->tq_lock, tq->tq_lock_flags);
while (!list_empty(&tq->tq_free_list)) {
t = list_entry(tq->tq_free_list.next, spl_task_t, t_list);
list_del_init(&t->t_list);
task_free(tq, t);
}
ASSERT(tq->tq_nthreads == 0);
ASSERT(tq->tq_nalloc == 0);
ASSERT(list_empty(&tq->tq_free_list));
ASSERT(list_empty(&tq->tq_work_list));
ASSERT(list_empty(&tq->tq_pend_list));
ASSERT(list_empty(&tq->tq_prio_list));
spin_unlock_irqrestore(&tq->tq_lock, tq->tq_lock_flags);
kmem_free(tq->tq_threads, nthreads * sizeof(spl_task_t *));
kmem_free(tq, sizeof(taskq_t));
SEXIT;
}
EXPORT_SYMBOL(__taskq_destroy);
int
spl_taskq_init(void)
{
SENTRY;
/* Solaris creates a dynamic taskq of up to 64 threads, however in
* a Linux environment 1 thread per-core is usually about right */
system_taskq = taskq_create("spl_system_taskq", num_online_cpus(),
minclsyspri, 4, 512, TASKQ_PREPOPULATE);
if (system_taskq == NULL)
SRETURN(1);
SRETURN(0);
}
void
spl_taskq_fini(void)
{
SENTRY;
taskq_destroy(system_taskq);
SEXIT;
}
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