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 void
  88 __cv_wait(kcondvar_t *cvp, kmutex_t *mp)
  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,
 107                                   TASK_UNINTERRUPTIBLE);
 108         atomic_inc(&cvp->cv_waiters);
 109
 110         /* Mutex should be dropped after prepare_to_wait() this
 111          * ensures we're linked in to the waiters list and avoids the
 112          * race where 'cvp->cv_waiters > 0' but the list is empty. */
 113         mutex_exit(mp);
 114         schedule();
 115         mutex_enter(mp);
 116
 117         atomic_dec(&cvp->cv_waiters);
 118         finish_wait(&cvp->cv_event, &wait);
 119         EXIT;
 120 }
 121 EXPORT_SYMBOL(__cv_wait);
 122
 123 /* 'expire_time' argument is an absolute wall clock time in jiffies.
 124  * Return value is time left (expire_time - now) or -1 if timeout occurred.
 125  */
 126 clock_t
 127 __cv_timedwait(kcondvar_t *cvp, kmutex_t *mp, clock_t expire_time)
 128 {
 129         DEFINE_WAIT(wait);
 130         clock_t time_left;
 131         ENTRY;
 132
 133         ASSERT(cvp);
 134         ASSERT(mp);
 135         ASSERT(cvp->cv_magic == CV_MAGIC);
 136         spin_lock(&cvp->cv_lock);
 137         ASSERT(mutex_owned(mp));
 138
 139         if (cvp->cv_mutex == NULL)
 140                 cvp->cv_mutex = mp;
 141
 142         /* Ensure the same mutex is used by all callers */
 143         ASSERT(cvp->cv_mutex == mp);
 144         spin_unlock(&cvp->cv_lock);
 145
 146         /* XXX - Does not handle jiffie wrap properly */
 147         time_left = expire_time - jiffies;
 148         if (time_left <= 0)
 149                 RETURN(-1);
 150
 151         prepare_to_wait_exclusive(&cvp->cv_event, &wait,
 152                                   TASK_UNINTERRUPTIBLE);
 153         atomic_inc(&cvp->cv_waiters);
 154
 155         /* Mutex should be dropped after prepare_to_wait() this
 156          * ensures we're linked in to the waiters list and avoids the
 157          * race where 'cvp->cv_waiters > 0' but the list is empty. */
 158         mutex_exit(mp);
 159         time_left = schedule_timeout(time_left);
 160         mutex_enter(mp);
 161
 162         atomic_dec(&cvp->cv_waiters);
 163         finish_wait(&cvp->cv_event, &wait);
 164
 165         RETURN(time_left > 0 ? time_left : -1);
 166 }
 167 EXPORT_SYMBOL(__cv_timedwait);
 168
 169 void
 170 __cv_signal(kcondvar_t *cvp)
 171 {
 172         ENTRY;
 173         ASSERT(cvp);
 174         ASSERT(cvp->cv_magic == CV_MAGIC);
 175
 176         /* All waiters are added with WQ_FLAG_EXCLUSIVE so only one
 177          * waiter will be set runable with each call to wake_up().
 178          * Additionally wake_up() holds a spin_lock assoicated with
 179          * the wait queue to ensure we don't race waking up processes. */
 180         if (atomic_read(&cvp->cv_waiters) > 0)
 181                 wake_up(&cvp->cv_event);
 182
 183         EXIT;
 184 }
 185 EXPORT_SYMBOL(__cv_signal);
 186
 187 void
 188 __cv_broadcast(kcondvar_t *cvp)
 189 {
 190         ASSERT(cvp);
 191         ASSERT(cvp->cv_magic == CV_MAGIC);
 192         ENTRY;
 193
 194         /* Wake_up_all() will wake up all waiters even those which
 195          * have the WQ_FLAG_EXCLUSIVE flag set. */
 196         if (atomic_read(&cvp->cv_waiters) > 0)
 197                 wake_up_all(&cvp->cv_event);
 198
 199         EXIT;
 200 }
 201 EXPORT_SYMBOL(__cv_broadcast);