zfs/lib/libzpool/taskq.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21 /*
  22  * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
  23  * Use is subject to license terms.
  24  */
  25
  26
  27
  28 #include <sys/zfs_context.h>
  29
  30 int taskq_now;
  31
  32 typedef struct task {
  33         struct task     *task_next;
  34         struct task     *task_prev;
  35         task_func_t     *task_func;
  36         void            *task_arg;
  37 } task_t;
  38
  39 #define TASKQ_ACTIVE    0x00010000
  40
  41 struct taskq {
  42         kmutex_t        tq_lock;
  43         krwlock_t       tq_threadlock;
  44         kcondvar_t      tq_dispatch_cv;
  45         kcondvar_t      tq_wait_cv;
  46         thread_t        *tq_threadlist;
  47         int             tq_flags;
  48         int             tq_active;
  49         int             tq_nthreads;
  50         int             tq_nalloc;
  51         int             tq_minalloc;
  52         int             tq_maxalloc;
  53         task_t          *tq_freelist;
  54         task_t          tq_task;
  55 };
  56
  57 static task_t *
  58 task_alloc(taskq_t *tq, int tqflags)
  59 {
  60         task_t *t;
  61
  62         if ((t = tq->tq_freelist) != NULL && tq->tq_nalloc >= tq->tq_minalloc) {
  63                 tq->tq_freelist = t->task_next;
  64         } else {
  65                 mutex_exit(&tq->tq_lock);
  66                 if (tq->tq_nalloc >= tq->tq_maxalloc) {
  67                         if (!(tqflags & KM_SLEEP)) {
  68                                 mutex_enter(&tq->tq_lock);
  69                                 return (NULL);
  70                         }
  71                         /*
  72                          * We don't want to exceed tq_maxalloc, but we can't
  73                          * wait for other tasks to complete (and thus free up
  74                          * task structures) without risking deadlock with
  75                          * the caller.  So, we just delay for one second
  76                          * to throttle the allocation rate.
  77                          */
  78                         delay(hz);
  79                 }
  80                 t = kmem_alloc(sizeof (task_t), tqflags);
  81                 mutex_enter(&tq->tq_lock);
  82                 if (t != NULL)
  83                         tq->tq_nalloc++;
  84         }
  85         return (t);
  86 }
  87
  88 static void
  89 task_free(taskq_t *tq, task_t *t)
  90 {
  91         if (tq->tq_nalloc <= tq->tq_minalloc) {
  92                 t->task_next = tq->tq_freelist;
  93                 tq->tq_freelist = t;
  94         } else {
  95                 tq->tq_nalloc--;
  96                 mutex_exit(&tq->tq_lock);
  97                 kmem_free(t, sizeof (task_t));
  98                 mutex_enter(&tq->tq_lock);
  99         }
 100 }
 101
 102 taskqid_t
 103 taskq_dispatch(taskq_t *tq, task_func_t func, void *arg, uint_t tqflags)
 104 {
 105         task_t *t;
 106
 107         if (taskq_now) {
 108                 func(arg);
 109                 return (1);
 110         }
 111
 112         mutex_enter(&tq->tq_lock);
 113         ASSERT(tq->tq_flags & TASKQ_ACTIVE);
 114         if ((t = task_alloc(tq, tqflags)) == NULL) {
 115                 mutex_exit(&tq->tq_lock);
 116                 return (0);
 117         }
 118         t->task_next = &tq->tq_task;
 119         t->task_prev = tq->tq_task.task_prev;
 120         t->task_next->task_prev = t;
 121         t->task_prev->task_next = t;
 122         t->task_func = func;
 123         t->task_arg = arg;
 124         cv_signal(&tq->tq_dispatch_cv);
 125         mutex_exit(&tq->tq_lock);
 126         return (1);
 127 }
 128
 129 void
 130 taskq_wait(taskq_t *tq)
 131 {
 132         mutex_enter(&tq->tq_lock);
 133         while (tq->tq_task.task_next != &tq->tq_task || tq->tq_active != 0)
 134                 cv_wait(&tq->tq_wait_cv, &tq->tq_lock);
 135         mutex_exit(&tq->tq_lock);
 136 }
 137
 138 static void *
 139 taskq_thread(void *arg)
 140 {
 141         taskq_t *tq = arg;
 142         task_t *t;
 143
 144         mutex_enter(&tq->tq_lock);
 145         while (tq->tq_flags & TASKQ_ACTIVE) {
 146                 if ((t = tq->tq_task.task_next) == &tq->tq_task) {
 147                         if (--tq->tq_active == 0)
 148                                 cv_broadcast(&tq->tq_wait_cv);
 149                         cv_wait(&tq->tq_dispatch_cv, &tq->tq_lock);
 150                         tq->tq_active++;
 151                         continue;
 152                 }
 153                 t->task_prev->task_next = t->task_next;
 154                 t->task_next->task_prev = t->task_prev;
 155                 mutex_exit(&tq->tq_lock);
 156
 157                 rw_enter(&tq->tq_threadlock, RW_READER);
 158                 t->task_func(t->task_arg);
 159                 rw_exit(&tq->tq_threadlock);
 160
 161                 mutex_enter(&tq->tq_lock);
 162                 task_free(tq, t);
 163         }
 164         tq->tq_nthreads--;
 165         cv_broadcast(&tq->tq_wait_cv);
 166         mutex_exit(&tq->tq_lock);
 167         return (NULL);
 168 }
 169
 170 /*ARGSUSED*/
 171 taskq_t *
 172 taskq_create(const char *name, int nthreads, pri_t pri,
 173         int minalloc, int maxalloc, uint_t flags)
 174 {
 175         taskq_t *tq = kmem_zalloc(sizeof (taskq_t), KM_SLEEP);
 176         int t;
 177
 178         rw_init(&tq->tq_threadlock, NULL, RW_DEFAULT, NULL);
 179         mutex_init(&tq->tq_lock, NULL, MUTEX_DEFAULT, NULL);
 180         cv_init(&tq->tq_dispatch_cv, NULL, CV_DEFAULT, NULL);
 181         cv_init(&tq->tq_wait_cv, NULL, CV_DEFAULT, NULL);
 182         tq->tq_flags = flags | TASKQ_ACTIVE;
 183         tq->tq_active = nthreads;
 184         tq->tq_nthreads = nthreads;
 185         tq->tq_minalloc = minalloc;
 186         tq->tq_maxalloc = maxalloc;
 187         tq->tq_task.task_next = &tq->tq_task;
 188         tq->tq_task.task_prev = &tq->tq_task;
 189         tq->tq_threadlist = kmem_alloc(nthreads * sizeof (thread_t), KM_SLEEP);
 190
 191         if (flags & TASKQ_PREPOPULATE) {
 192                 mutex_enter(&tq->tq_lock);
 193                 while (minalloc-- > 0)
 194                         task_free(tq, task_alloc(tq, KM_SLEEP));
 195                 mutex_exit(&tq->tq_lock);
 196         }
 197
 198         for (t = 0; t < nthreads; t++)
 199                 VERIFY(thr_create(0, 0, taskq_thread,
 200                     tq, THR_BOUND, &tq->tq_threadlist[t]) == 0);
 201
 202         return (tq);
 203 }
 204
 205 void
 206 taskq_destroy(taskq_t *tq)
 207 {
 208         int t;
 209         int nthreads = tq->tq_nthreads;
 210
 211         taskq_wait(tq);
 212
 213         mutex_enter(&tq->tq_lock);
 214
 215         tq->tq_flags &= ~TASKQ_ACTIVE;
 216         cv_broadcast(&tq->tq_dispatch_cv);
 217
 218         while (tq->tq_nthreads != 0)
 219                 cv_wait(&tq->tq_wait_cv, &tq->tq_lock);
 220
 221         tq->tq_minalloc = 0;
 222         while (tq->tq_nalloc != 0) {
 223                 ASSERT(tq->tq_freelist != NULL);
 224                 task_free(tq, task_alloc(tq, KM_SLEEP));
 225         }
 226
 227         mutex_exit(&tq->tq_lock);
 228
 229         for (t = 0; t < nthreads; t++)
 230                 VERIFY(thr_join(tq->tq_threadlist[t], NULL, NULL) == 0);
 231
 232         kmem_free(tq->tq_threadlist, nthreads * sizeof (thread_t));
 233
 234         rw_destroy(&tq->tq_threadlock);
 235         mutex_destroy(&tq->tq_lock);
 236         cv_destroy(&tq->tq_dispatch_cv);
 237         cv_destroy(&tq->tq_wait_cv);
 238
 239         kmem_free(tq, sizeof (taskq_t));
 240 }
 241
 242 int
 243 taskq_member(taskq_t *tq, void *t)
 244 {
 245         int i;
 246
 247         if (taskq_now)
 248                 return (1);
 249
 250         for (i = 0; i < tq->tq_nthreads; i++)
 251                 if (tq->tq_threadlist[i] == (thread_t)(uintptr_t)t)
 252                         return (1);
 253
 254         return (0);
 255 }