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 == NULL);
  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         atomic_set(&cvp->cv_refs, 1);
  52         cvp->cv_mutex = NULL;
  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         SEXIT;
  61 }
  62 EXPORT_SYMBOL(__cv_init);
  63
  64 static int
  65 cv_destroy_wakeup(kcondvar_t *cvp)
  66 {
  67         if (!atomic_read(&cvp->cv_waiters) && !atomic_read(&cvp->cv_refs)) {
  68                 ASSERT(cvp->cv_mutex == NULL);
  69                 ASSERT(!waitqueue_active(&cvp->cv_event));
  70                 return 1;
  71         }
  72
  73         return 0;
  74 }
  75
  76 void
  77 __cv_destroy(kcondvar_t *cvp)
  78 {
  79         SENTRY;
  80         ASSERT(cvp);
  81         ASSERT(cvp->cv_magic == CV_MAGIC);
  82
  83         cvp->cv_magic = CV_DESTROY;
  84         atomic_dec(&cvp->cv_refs);
  85
  86         /* Block until all waiters are woken and references dropped. */
  87         while (cv_destroy_wakeup(cvp) == 0)
  88                 wait_event_timeout(cvp->cv_destroy, cv_destroy_wakeup(cvp), 1);
  89
  90         ASSERT3P(cvp->cv_mutex, ==, NULL);
  91         ASSERT3S(atomic_read(&cvp->cv_refs), ==, 0);
  92         ASSERT3S(atomic_read(&cvp->cv_waiters), ==, 0);
  93         ASSERT3S(waitqueue_active(&cvp->cv_event), ==, 0);
  94
  95         SEXIT;
  96 }
  97 EXPORT_SYMBOL(__cv_destroy);
  98
  99 static void
 100 cv_wait_common(kcondvar_t *cvp, kmutex_t *mp, int state, int io)
 101 {
 102         DEFINE_WAIT(wait);
 103         SENTRY;
 104
 105         ASSERT(cvp);
 106         ASSERT(mp);
 107         ASSERT(cvp->cv_magic == CV_MAGIC);
 108         ASSERT(mutex_owned(mp));
 109         atomic_inc(&cvp->cv_refs);
 110
 111         if (cvp->cv_mutex == NULL)
 112                 cvp->cv_mutex = mp;
 113
 114         /* Ensure the same mutex is used by all callers */
 115         ASSERT(cvp->cv_mutex == mp);
 116
 117         prepare_to_wait_exclusive(&cvp->cv_event, &wait, state);
 118         atomic_inc(&cvp->cv_waiters);
 119
 120         /* Mutex should be dropped after prepare_to_wait() this
 121          * ensures we're linked in to the waiters list and avoids the
 122          * race where 'cvp->cv_waiters > 0' but the list is empty. */
 123         mutex_exit(mp);
 124         if (io)
 125                 io_schedule();
 126         else
 127                 schedule();
 128         mutex_enter(mp);
 129
 130         /* No more waiters a different mutex could be used */
 131         if (atomic_dec_and_test(&cvp->cv_waiters)) {
 132                 cvp->cv_mutex = NULL;
 133                 wake_up(&cvp->cv_destroy);
 134         }
 135
 136         finish_wait(&cvp->cv_event, &wait);
 137         atomic_dec(&cvp->cv_refs);
 138
 139         SEXIT;
 140 }
 141
 142 void
 143 __cv_wait(kcondvar_t *cvp, kmutex_t *mp)
 144 {
 145         cv_wait_common(cvp, mp, TASK_UNINTERRUPTIBLE, 0);
 146 }
 147 EXPORT_SYMBOL(__cv_wait);
 148
 149 void
 150 __cv_wait_interruptible(kcondvar_t *cvp, kmutex_t *mp)
 151 {
 152         cv_wait_common(cvp, mp, TASK_INTERRUPTIBLE, 0);
 153 }
 154 EXPORT_SYMBOL(__cv_wait_interruptible);
 155
 156 void
 157 __cv_wait_io(kcondvar_t *cvp, kmutex_t *mp)
 158 {
 159         cv_wait_common(cvp, mp, TASK_UNINTERRUPTIBLE, 1);
 160 }
 161 EXPORT_SYMBOL(__cv_wait_io);
 162
 163 /* 'expire_time' argument is an absolute wall clock time in jiffies.
 164  * Return value is time left (expire_time - now) or -1 if timeout occurred.
 165  */
 166 static clock_t
 167 __cv_timedwait_common(kcondvar_t *cvp, kmutex_t *mp,
 168                       clock_t expire_time, int state)
 169 {
 170         DEFINE_WAIT(wait);
 171         clock_t time_left;
 172         SENTRY;
 173
 174         ASSERT(cvp);
 175         ASSERT(mp);
 176         ASSERT(cvp->cv_magic == CV_MAGIC);
 177         ASSERT(mutex_owned(mp));
 178         atomic_inc(&cvp->cv_refs);
 179
 180         if (cvp->cv_mutex == NULL)
 181                 cvp->cv_mutex = mp;
 182
 183         /* Ensure the same mutex is used by all callers */
 184         ASSERT(cvp->cv_mutex == mp);
 185
 186         /* XXX - Does not handle jiffie wrap properly */
 187         time_left = expire_time - jiffies;
 188         if (time_left <= 0) {
 189                 atomic_dec(&cvp->cv_refs);
 190                 SRETURN(-1);
 191         }
 192
 193         prepare_to_wait_exclusive(&cvp->cv_event, &wait, state);
 194         atomic_inc(&cvp->cv_waiters);
 195
 196         /* Mutex should be dropped after prepare_to_wait() this
 197          * ensures we're linked in to the waiters list and avoids the
 198          * race where 'cvp->cv_waiters > 0' but the list is empty. */
 199         mutex_exit(mp);
 200         time_left = schedule_timeout(time_left);
 201         mutex_enter(mp);
 202
 203         /* No more waiters a different mutex could be used */
 204         if (atomic_dec_and_test(&cvp->cv_waiters)) {
 205                 cvp->cv_mutex = NULL;
 206                 wake_up(&cvp->cv_destroy);
 207         }
 208
 209         finish_wait(&cvp->cv_event, &wait);
 210         atomic_dec(&cvp->cv_refs);
 211
 212         SRETURN(time_left > 0 ? time_left : -1);
 213 }
 214
 215 clock_t
 216 __cv_timedwait(kcondvar_t *cvp, kmutex_t *mp, clock_t exp_time)
 217 {
 218         return __cv_timedwait_common(cvp, mp, exp_time, TASK_UNINTERRUPTIBLE);
 219 }
 220 EXPORT_SYMBOL(__cv_timedwait);
 221
 222 clock_t
 223 __cv_timedwait_interruptible(kcondvar_t *cvp, kmutex_t *mp, clock_t exp_time)
 224 {
 225         return __cv_timedwait_common(cvp, mp, exp_time, TASK_INTERRUPTIBLE);
 226 }
 227 EXPORT_SYMBOL(__cv_timedwait_interruptible);
 228
 229 void
 230 __cv_signal(kcondvar_t *cvp)
 231 {
 232         SENTRY;
 233         ASSERT(cvp);
 234         ASSERT(cvp->cv_magic == CV_MAGIC);
 235         atomic_inc(&cvp->cv_refs);
 236
 237         /* All waiters are added with WQ_FLAG_EXCLUSIVE so only one
 238          * waiter will be set runable with each call to wake_up().
 239          * Additionally wake_up() holds a spin_lock assoicated with
 240          * the wait queue to ensure we don't race waking up processes. */
 241         if (atomic_read(&cvp->cv_waiters) > 0)
 242                 wake_up(&cvp->cv_event);
 243
 244         atomic_dec(&cvp->cv_refs);
 245         SEXIT;
 246 }
 247 EXPORT_SYMBOL(__cv_signal);
 248
 249 void
 250 __cv_broadcast(kcondvar_t *cvp)
 251 {
 252         SENTRY;
 253         ASSERT(cvp);
 254         ASSERT(cvp->cv_magic == CV_MAGIC);
 255         atomic_inc(&cvp->cv_refs);
 256
 257         /* Wake_up_all() will wake up all waiters even those which
 258          * have the WQ_FLAG_EXCLUSIVE flag set. */
 259         if (atomic_read(&cvp->cv_waiters) > 0)
 260                 wake_up_all(&cvp->cv_event);
 261
 262         atomic_dec(&cvp->cv_refs);
 263         SEXIT;
 264 }
 265 EXPORT_SYMBOL(__cv_broadcast);