module/spl/spl-condvar.c

   1 /*****************************************************************************\
   2  *  Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC.
   3  *  Copyright (C) 2007 The Regents of the University of California.
   4  *  Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
   5  *  Written by Brian Behlendorf <behlendorf1@llnl.gov>.
   6  *  UCRL-CODE-235197
   7  *
   8  *  This file is part of the SPL, Solaris Porting Layer.
   9  *  For details, see <http://github.com/behlendorf/spl/>.
  10  *
  11  *  The SPL is free software; you can redistribute it and/or modify it
  12  *  under the terms of the GNU General Public License as published by the
  13  *  Free Software Foundation; either version 2 of the License, or (at your
  14  *  option) any later version.
  15  *
  16  *  The SPL is distributed in the hope that it will be useful, but WITHOUT
  17  *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  18  *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  19  *  for more details.
  20  *
  21  *  You should have received a copy of the GNU General Public License along
  22  *  with the SPL.  If not, see <http://www.gnu.org/licenses/>.
  23  *****************************************************************************
  24  *  Solaris Porting Layer (SPL) Credential Implementation.
  25 \*****************************************************************************/
  26
  27 #include <sys/condvar.h>
  28 #include <spl-debug.h>
  29
  30 #ifdef DEBUG_SUBSYSTEM
  31 #undef DEBUG_SUBSYSTEM
  32 #endif
  33
  34 #define DEBUG_SUBSYSTEM S_CONDVAR
  35
  36 void
  37 __cv_init(kcondvar_t *cvp, char *name, kcv_type_t type, void *arg)
  38 {
  39         int flags = KM_SLEEP;
  40
  41         ENTRY;
  42         ASSERT(cvp);
  43         ASSERT(name);
  44         ASSERT(type == CV_DEFAULT);
  45         ASSERT(arg == NULL);
  46
  47         cvp->cv_magic = CV_MAGIC;
  48         init_waitqueue_head(&cvp->cv_event);
  49         spin_lock_init(&cvp->cv_lock);
  50         atomic_set(&cvp->cv_waiters, 0);
  51         cvp->cv_mutex = NULL;
  52         cvp->cv_name = NULL;
  53         cvp->cv_name_size = strlen(name) + 1;
  54
  55         /* We may be called when there is a non-zero preempt_count or
  56          * interrupts are disabled is which case we must not sleep.
  57          */
  58         if (current_thread_info()->preempt_count || irqs_disabled())
  59                 flags = KM_NOSLEEP;
  60
  61         cvp->cv_name = kmem_alloc(cvp->cv_name_size, flags);
  62         if (cvp->cv_name)
  63                 strcpy(cvp->cv_name, name);
  64
  65         EXIT;
  66 }
  67 EXPORT_SYMBOL(__cv_init);
  68
  69 void
  70 __cv_destroy(kcondvar_t *cvp)
  71 {
  72         ENTRY;
  73         ASSERT(cvp);
  74         ASSERT(cvp->cv_magic == CV_MAGIC);
  75         spin_lock(&cvp->cv_lock);
  76         ASSERT(atomic_read(&cvp->cv_waiters) == 0);
  77         ASSERT(!waitqueue_active(&cvp->cv_event));
  78
  79         if (cvp->cv_name)
  80                 kmem_free(cvp->cv_name, cvp->cv_name_size);
  81
  82         spin_unlock(&cvp->cv_lock);
  83         memset(cvp, CV_POISON, sizeof(*cvp));
  84         EXIT;
  85 }
  86 EXPORT_SYMBOL(__cv_destroy);
  87
  88 static void
  89 cv_wait_common(kcondvar_t *cvp, kmutex_t *mp, int state)
  90 {
  91         DEFINE_WAIT(wait);
  92         ENTRY;
  93
  94         ASSERT(cvp);
  95         ASSERT(mp);
  96         ASSERT(cvp->cv_magic == CV_MAGIC);
  97         spin_lock(&cvp->cv_lock);
  98         ASSERT(mutex_owned(mp));
  99
 100         if (cvp->cv_mutex == NULL)
 101                 cvp->cv_mutex = mp;
 102
 103         /* Ensure the same mutex is used by all callers */
 104         ASSERT(cvp->cv_mutex == mp);
 105         spin_unlock(&cvp->cv_lock);
 106
 107         prepare_to_wait_exclusive(&cvp->cv_event, &wait, state);
 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
 122 void
 123 __cv_wait(kcondvar_t *cvp, kmutex_t *mp)
 124 {
 125         cv_wait_common(cvp, mp, TASK_UNINTERRUPTIBLE);
 126 }
 127 EXPORT_SYMBOL(__cv_wait);
 128
 129 void
 130 __cv_wait_interruptible(kcondvar_t *cvp, kmutex_t *mp)
 131 {
 132         cv_wait_common(cvp, mp, TASK_INTERRUPTIBLE);
 133 }
 134 EXPORT_SYMBOL(__cv_wait_interruptible);
 135
 136 /* 'expire_time' argument is an absolute wall clock time in jiffies.
 137  * Return value is time left (expire_time - now) or -1 if timeout occurred.
 138  */
 139 clock_t
 140 __cv_timedwait(kcondvar_t *cvp, kmutex_t *mp, clock_t expire_time)
 141 {
 142         DEFINE_WAIT(wait);
 143         clock_t time_left;
 144         ENTRY;
 145
 146         ASSERT(cvp);
 147         ASSERT(mp);
 148         ASSERT(cvp->cv_magic == CV_MAGIC);
 149         spin_lock(&cvp->cv_lock);
 150         ASSERT(mutex_owned(mp));
 151
 152         if (cvp->cv_mutex == NULL)
 153                 cvp->cv_mutex = mp;
 154
 155         /* Ensure the same mutex is used by all callers */
 156         ASSERT(cvp->cv_mutex == mp);
 157         spin_unlock(&cvp->cv_lock);
 158
 159         /* XXX - Does not handle jiffie wrap properly */
 160         time_left = expire_time - jiffies;
 161         if (time_left <= 0)
 162                 RETURN(-1);
 163
 164         prepare_to_wait_exclusive(&cvp->cv_event, &wait,
 165                                   TASK_UNINTERRUPTIBLE);
 166         atomic_inc(&cvp->cv_waiters);
 167
 168         /* Mutex should be dropped after prepare_to_wait() this
 169          * ensures we're linked in to the waiters list and avoids the
 170          * race where 'cvp->cv_waiters > 0' but the list is empty. */
 171         mutex_exit(mp);
 172         time_left = schedule_timeout(time_left);
 173         mutex_enter(mp);
 174
 175         atomic_dec(&cvp->cv_waiters);
 176         finish_wait(&cvp->cv_event, &wait);
 177
 178         RETURN(time_left > 0 ? time_left : -1);
 179 }
 180 EXPORT_SYMBOL(__cv_timedwait);
 181
 182 void
 183 __cv_signal(kcondvar_t *cvp)
 184 {
 185         ENTRY;
 186         ASSERT(cvp);
 187         ASSERT(cvp->cv_magic == CV_MAGIC);
 188
 189         /* All waiters are added with WQ_FLAG_EXCLUSIVE so only one
 190          * waiter will be set runable with each call to wake_up().
 191          * Additionally wake_up() holds a spin_lock assoicated with
 192          * the wait queue to ensure we don't race waking up processes. */
 193         if (atomic_read(&cvp->cv_waiters) > 0)
 194                 wake_up(&cvp->cv_event);
 195
 196         EXIT;
 197 }
 198 EXPORT_SYMBOL(__cv_signal);
 199
 200 void
 201 __cv_broadcast(kcondvar_t *cvp)
 202 {
 203         ASSERT(cvp);
 204         ASSERT(cvp->cv_magic == CV_MAGIC);
 205         ENTRY;
 206
 207         /* Wake_up_all() will wake up all waiters even those which
 208          * have the WQ_FLAG_EXCLUSIVE flag set. */
 209         if (atomic_read(&cvp->cv_waiters) > 0)
 210                 wake_up_all(&cvp->cv_event);
 211
 212         EXIT;
 213 }
 214 EXPORT_SYMBOL(__cv_broadcast);