module/spl/spl-condvar.c

   1 /*
   2  *  This file is part of the SPL: Solaris Porting Layer.
   3  *
   4  *  Copyright (c) 2008 Lawrence Livermore National Security, LLC.
   5  *  Produced at Lawrence Livermore National Laboratory
   6  *  Written by:
   7  *          Brian Behlendorf <behlendorf1@llnl.gov>,
   8  *          Herb Wartens <wartens2@llnl.gov>,
   9  *          Jim Garlick <garlick@llnl.gov>
  10  *  UCRL-CODE-235197
  11  *
  12  *  This is free software; you can redistribute it and/or modify it
  13  *  under the terms of the GNU General Public License as published by
  14  *  the Free Software Foundation; either version 2 of the License, or
  15  *  (at your option) any later version.
  16  *
  17  *  This is distributed in the hope that it will be useful, but WITHOUT
  18  *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  19  *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  20  *  for more details.
  21  *
  22  *  You should have received a copy of the GNU General Public License along
  23  *  with this program; if not, write to the Free Software Foundation, Inc.,
  24  *  51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA.
  25  */
  26
  27 #include <sys/condvar.h>
  28
  29 #ifdef DEBUG_SUBSYSTEM
  30 #undef DEBUG_SUBSYSTEM
  31 #endif
  32
  33 #define DEBUG_SUBSYSTEM S_CONDVAR
  34
  35 void
  36 __cv_init(kcondvar_t *cvp, char *name, kcv_type_t type, void *arg)
  37 {
  38         int flags = KM_SLEEP;
  39
  40         ENTRY;
  41         ASSERT(cvp);
  42         ASSERT(name);
  43         ASSERT(type == CV_DEFAULT);
  44         ASSERT(arg == NULL);
  45
  46         cvp->cv_magic = CV_MAGIC;
  47         init_waitqueue_head(&cvp->cv_event);
  48         spin_lock_init(&cvp->cv_lock);
  49         atomic_set(&cvp->cv_waiters, 0);
  50         cvp->cv_mutex = NULL;
  51         cvp->cv_name = NULL;
  52         cvp->cv_name_size = strlen(name) + 1;
  53
  54         /* We may be called when there is a non-zero preempt_count or
  55          * interrupts are disabled is which case we must not sleep.
  56          */
  57         if (current_thread_info()->preempt_count || irqs_disabled())
  58                 flags = KM_NOSLEEP;
  59
  60         cvp->cv_name = kmem_alloc(cvp->cv_name_size, flags);
  61         if (cvp->cv_name)
  62                 strcpy(cvp->cv_name, name);
  63
  64         EXIT;
  65 }
  66 EXPORT_SYMBOL(__cv_init);
  67
  68 void
  69 __cv_destroy(kcondvar_t *cvp)
  70 {
  71         ENTRY;
  72         ASSERT(cvp);
  73         ASSERT(cvp->cv_magic == CV_MAGIC);
  74         spin_lock(&cvp->cv_lock);
  75         ASSERT(atomic_read(&cvp->cv_waiters) == 0);
  76         ASSERT(!waitqueue_active(&cvp->cv_event));
  77
  78         if (cvp->cv_name)
  79                 kmem_free(cvp->cv_name, cvp->cv_name_size);
  80
  81         spin_unlock(&cvp->cv_lock);
  82         memset(cvp, CV_POISON, sizeof(*cvp));
  83         EXIT;
  84 }
  85 EXPORT_SYMBOL(__cv_destroy);
  86
  87 static void
  88 cv_wait_common(kcondvar_t *cvp, kmutex_t *mp, int state)
  89 {
  90         DEFINE_WAIT(wait);
  91         ENTRY;
  92
  93         ASSERT(cvp);
  94         ASSERT(mp);
  95         ASSERT(cvp->cv_magic == CV_MAGIC);
  96         spin_lock(&cvp->cv_lock);
  97         ASSERT(mutex_owned(mp));
  98
  99         if (cvp->cv_mutex == NULL)
 100                 cvp->cv_mutex = mp;
 101
 102         /* Ensure the same mutex is used by all callers */
 103         ASSERT(cvp->cv_mutex == mp);
 104         spin_unlock(&cvp->cv_lock);
 105
 106         prepare_to_wait_exclusive(&cvp->cv_event, &wait, state);
 107         atomic_inc(&cvp->cv_waiters);
 108
 109         /* Mutex should be dropped after prepare_to_wait() this
 110          * ensures we're linked in to the waiters list and avoids the
 111          * race where 'cvp->cv_waiters > 0' but the list is empty. */
 112         mutex_exit(mp);
 113         schedule();
 114         mutex_enter(mp);
 115
 116         atomic_dec(&cvp->cv_waiters);
 117         finish_wait(&cvp->cv_event, &wait);
 118         EXIT;
 119 }
 120
 121 void
 122 __cv_wait(kcondvar_t *cvp, kmutex_t *mp)
 123 {
 124         cv_wait_common(cvp, mp, TASK_UNINTERRUPTIBLE);
 125 }
 126 EXPORT_SYMBOL(__cv_wait);
 127
 128 void
 129 __cv_wait_interruptible(kcondvar_t *cvp, kmutex_t *mp)
 130 {
 131         cv_wait_common(cvp, mp, TASK_INTERRUPTIBLE);
 132 }
 133 EXPORT_SYMBOL(__cv_wait_interruptible);
 134
 135 /* 'expire_time' argument is an absolute wall clock time in jiffies.
 136  * Return value is time left (expire_time - now) or -1 if timeout occurred.
 137  */
 138 clock_t
 139 __cv_timedwait(kcondvar_t *cvp, kmutex_t *mp, clock_t expire_time)
 140 {
 141         DEFINE_WAIT(wait);
 142         clock_t time_left;
 143         ENTRY;
 144
 145         ASSERT(cvp);
 146         ASSERT(mp);
 147         ASSERT(cvp->cv_magic == CV_MAGIC);
 148         spin_lock(&cvp->cv_lock);
 149         ASSERT(mutex_owned(mp));
 150
 151         if (cvp->cv_mutex == NULL)
 152                 cvp->cv_mutex = mp;
 153
 154         /* Ensure the same mutex is used by all callers */
 155         ASSERT(cvp->cv_mutex == mp);
 156         spin_unlock(&cvp->cv_lock);
 157
 158         /* XXX - Does not handle jiffie wrap properly */
 159         time_left = expire_time - jiffies;
 160         if (time_left <= 0)
 161                 RETURN(-1);
 162
 163         prepare_to_wait_exclusive(&cvp->cv_event, &wait,
 164                                   TASK_UNINTERRUPTIBLE);
 165         atomic_inc(&cvp->cv_waiters);
 166
 167         /* Mutex should be dropped after prepare_to_wait() this
 168          * ensures we're linked in to the waiters list and avoids the
 169          * race where 'cvp->cv_waiters > 0' but the list is empty. */
 170         mutex_exit(mp);
 171         time_left = schedule_timeout(time_left);
 172         mutex_enter(mp);
 173
 174         atomic_dec(&cvp->cv_waiters);
 175         finish_wait(&cvp->cv_event, &wait);
 176
 177         RETURN(time_left > 0 ? time_left : -1);
 178 }
 179 EXPORT_SYMBOL(__cv_timedwait);
 180
 181 void
 182 __cv_signal(kcondvar_t *cvp)
 183 {
 184         ENTRY;
 185         ASSERT(cvp);
 186         ASSERT(cvp->cv_magic == CV_MAGIC);
 187
 188         /* All waiters are added with WQ_FLAG_EXCLUSIVE so only one
 189          * waiter will be set runable with each call to wake_up().
 190          * Additionally wake_up() holds a spin_lock assoicated with
 191          * the wait queue to ensure we don't race waking up processes. */
 192         if (atomic_read(&cvp->cv_waiters) > 0)
 193                 wake_up(&cvp->cv_event);
 194
 195         EXIT;
 196 }
 197 EXPORT_SYMBOL(__cv_signal);
 198
 199 void
 200 __cv_broadcast(kcondvar_t *cvp)
 201 {
 202         ASSERT(cvp);
 203         ASSERT(cvp->cv_magic == CV_MAGIC);
 204         ENTRY;
 205
 206         /* Wake_up_all() will wake up all waiters even those which
 207          * have the WQ_FLAG_EXCLUSIVE flag set. */
 208         if (atomic_read(&cvp->cv_waiters) > 0)
 209                 wake_up_all(&cvp->cv_event);
 210
 211         EXIT;
 212 }
 213 EXPORT_SYMBOL(__cv_broadcast);