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 SS_DEBUG_SUBSYS
  31 #undef SS_DEBUG_SUBSYS
  32 #endif
  33
  34 #define SS_DEBUG_SUBSYS SS_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         SENTRY;
  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         init_waitqueue_head(&cvp->cv_destroy);
  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         SEXIT;
  66 }
  67 EXPORT_SYMBOL(__cv_init);
  68
  69 static int
  70 cv_destroy_wakeup(kcondvar_t *cvp)
  71 {
  72         if ((waitqueue_active(&cvp->cv_event)) ||
  73             (atomic_read(&cvp->cv_waiters) > 0))
  74                 return 0;
  75
  76         return 1;
  77 }
  78
  79 void
  80 __cv_destroy(kcondvar_t *cvp)
  81 {
  82         SENTRY;
  83         ASSERT(cvp);
  84         ASSERT(cvp->cv_magic == CV_MAGIC);
  85
  86         /* Block until all waiters have woken */
  87         while (cv_destroy_wakeup(cvp) == 0)
  88                 wait_event_timeout(cvp->cv_destroy, cv_destroy_wakeup(cvp), 1);
  89
  90         ASSERT(cvp->cv_mutex == NULL);
  91         ASSERT(atomic_read(&cvp->cv_waiters) == 0);
  92         ASSERT(!waitqueue_active(&cvp->cv_event));
  93
  94         if (cvp->cv_name)
  95                 kmem_free(cvp->cv_name, cvp->cv_name_size);
  96
  97         SEXIT;
  98 }
  99 EXPORT_SYMBOL(__cv_destroy);
 100
 101 static void
 102 cv_wait_common(kcondvar_t *cvp, kmutex_t *mp, int state)
 103 {
 104         DEFINE_WAIT(wait);
 105         SENTRY;
 106
 107         ASSERT(cvp);
 108         ASSERT(mp);
 109         ASSERT(cvp->cv_magic == CV_MAGIC);
 110         ASSERT(mutex_owned(mp));
 111
 112         if (cvp->cv_mutex == NULL)
 113                 cvp->cv_mutex = mp;
 114
 115         /* Ensure the same mutex is used by all callers */
 116         ASSERT(cvp->cv_mutex == mp);
 117
 118         prepare_to_wait_exclusive(&cvp->cv_event, &wait, state);
 119         atomic_inc(&cvp->cv_waiters);
 120
 121         /* Mutex should be dropped after prepare_to_wait() this
 122          * ensures we're linked in to the waiters list and avoids the
 123          * race where 'cvp->cv_waiters > 0' but the list is empty. */
 124         mutex_exit(mp);
 125         schedule();
 126         mutex_enter(mp);
 127
 128         /* No more waiters a different mutex could be used */
 129         if (atomic_dec_and_test(&cvp->cv_waiters)) {
 130                 cvp->cv_mutex = NULL;
 131                 wake_up(&cvp->cv_destroy);
 132         }
 133
 134         finish_wait(&cvp->cv_event, &wait);
 135
 136         SEXIT;
 137 }
 138
 139 void
 140 __cv_wait(kcondvar_t *cvp, kmutex_t *mp)
 141 {
 142         cv_wait_common(cvp, mp, TASK_UNINTERRUPTIBLE);
 143 }
 144 EXPORT_SYMBOL(__cv_wait);
 145
 146 void
 147 __cv_wait_interruptible(kcondvar_t *cvp, kmutex_t *mp)
 148 {
 149         cv_wait_common(cvp, mp, TASK_INTERRUPTIBLE);
 150 }
 151 EXPORT_SYMBOL(__cv_wait_interruptible);
 152
 153 /* 'expire_time' argument is an absolute wall clock time in jiffies.
 154  * Return value is time left (expire_time - now) or -1 if timeout occurred.
 155  */
 156 static clock_t
 157 __cv_timedwait_common(kcondvar_t *cvp, kmutex_t *mp,
 158                       clock_t expire_time, int state)
 159 {
 160         DEFINE_WAIT(wait);
 161         clock_t time_left;
 162         SENTRY;
 163
 164         ASSERT(cvp);
 165         ASSERT(mp);
 166         ASSERT(cvp->cv_magic == CV_MAGIC);
 167         ASSERT(mutex_owned(mp));
 168
 169         if (cvp->cv_mutex == NULL)
 170                 cvp->cv_mutex = mp;
 171
 172         /* Ensure the same mutex is used by all callers */
 173         ASSERT(cvp->cv_mutex == mp);
 174
 175         /* XXX - Does not handle jiffie wrap properly */
 176         time_left = expire_time - jiffies;
 177         if (time_left <= 0)
 178                 SRETURN(-1);
 179
 180         prepare_to_wait_exclusive(&cvp->cv_event, &wait, state);
 181         atomic_inc(&cvp->cv_waiters);
 182
 183         /* Mutex should be dropped after prepare_to_wait() this
 184          * ensures we're linked in to the waiters list and avoids the
 185          * race where 'cvp->cv_waiters > 0' but the list is empty. */
 186         mutex_exit(mp);
 187         time_left = schedule_timeout(time_left);
 188         mutex_enter(mp);
 189
 190         /* No more waiters a different mutex could be used */
 191         if (atomic_dec_and_test(&cvp->cv_waiters)) {
 192                 cvp->cv_mutex = NULL;
 193                 wake_up(&cvp->cv_destroy);
 194         }
 195
 196         finish_wait(&cvp->cv_event, &wait);
 197
 198         SRETURN(time_left > 0 ? time_left : -1);
 199 }
 200
 201 clock_t
 202 __cv_timedwait(kcondvar_t *cvp, kmutex_t *mp, clock_t exp_time)
 203 {
 204         return __cv_timedwait_common(cvp, mp, exp_time, TASK_UNINTERRUPTIBLE);
 205 }
 206 EXPORT_SYMBOL(__cv_timedwait);
 207
 208 clock_t
 209 __cv_timedwait_interruptible(kcondvar_t *cvp, kmutex_t *mp, clock_t exp_time)
 210 {
 211         return __cv_timedwait_common(cvp, mp, exp_time, TASK_INTERRUPTIBLE);
 212 }
 213 EXPORT_SYMBOL(__cv_timedwait_interruptible);
 214
 215 void
 216 __cv_signal(kcondvar_t *cvp)
 217 {
 218         SENTRY;
 219         ASSERT(cvp);
 220         ASSERT(cvp->cv_magic == CV_MAGIC);
 221
 222         /* All waiters are added with WQ_FLAG_EXCLUSIVE so only one
 223          * waiter will be set runable with each call to wake_up().
 224          * Additionally wake_up() holds a spin_lock assoicated with
 225          * the wait queue to ensure we don't race waking up processes. */
 226         if (atomic_read(&cvp->cv_waiters) > 0)
 227                 wake_up(&cvp->cv_event);
 228
 229         SEXIT;
 230 }
 231 EXPORT_SYMBOL(__cv_signal);
 232
 233 void
 234 __cv_broadcast(kcondvar_t *cvp)
 235 {
 236         ASSERT(cvp);
 237         ASSERT(cvp->cv_magic == CV_MAGIC);
 238         SENTRY;
 239
 240         /* Wake_up_all() will wake up all waiters even those which
 241          * have the WQ_FLAG_EXCLUSIVE flag set. */
 242         if (atomic_read(&cvp->cv_waiters) > 0)
 243                 wake_up_all(&cvp->cv_event);
 244
 245         SEXIT;
 246 }
 247 EXPORT_SYMBOL(__cv_broadcast);