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         cvp->cv_mutex = NULL;
  52
  53         /* We may be called when there is a non-zero preempt_count or
  54          * interrupts are disabled is which case we must not sleep.
  55          */
  56         if (current_thread_info()->preempt_count || irqs_disabled())
  57                 flags = KM_NOSLEEP;
  58
  59         SEXIT;
  60 }
  61 EXPORT_SYMBOL(__cv_init);
  62
  63 static int
  64 cv_destroy_wakeup(kcondvar_t *cvp)
  65 {
  66         if ((waitqueue_active(&cvp->cv_event)) ||
  67             (atomic_read(&cvp->cv_waiters) > 0))
  68                 return 0;
  69
  70         return 1;
  71 }
  72
  73 void
  74 __cv_destroy(kcondvar_t *cvp)
  75 {
  76         SENTRY;
  77         ASSERT(cvp);
  78         ASSERT(cvp->cv_magic == CV_MAGIC);
  79
  80         /* Block until all waiters have woken */
  81         while (cv_destroy_wakeup(cvp) == 0)
  82                 wait_event_timeout(cvp->cv_destroy, cv_destroy_wakeup(cvp), 1);
  83
  84         ASSERT(cvp->cv_mutex == NULL);
  85         ASSERT(atomic_read(&cvp->cv_waiters) == 0);
  86         ASSERT(!waitqueue_active(&cvp->cv_event));
  87
  88         SEXIT;
  89 }
  90 EXPORT_SYMBOL(__cv_destroy);
  91
  92 static void
  93 cv_wait_common(kcondvar_t *cvp, kmutex_t *mp, int state)
  94 {
  95         DEFINE_WAIT(wait);
  96         SENTRY;
  97
  98         ASSERT(cvp);
  99         ASSERT(mp);
 100         ASSERT(cvp->cv_magic == CV_MAGIC);
 101         ASSERT(mutex_owned(mp));
 102
 103         if (cvp->cv_mutex == NULL)
 104                 cvp->cv_mutex = mp;
 105
 106         /* Ensure the same mutex is used by all callers */
 107         ASSERT(cvp->cv_mutex == mp);
 108
 109         prepare_to_wait_exclusive(&cvp->cv_event, &wait, state);
 110         atomic_inc(&cvp->cv_waiters);
 111
 112         /* Mutex should be dropped after prepare_to_wait() this
 113          * ensures we're linked in to the waiters list and avoids the
 114          * race where 'cvp->cv_waiters > 0' but the list is empty. */
 115         mutex_exit(mp);
 116         schedule();
 117         mutex_enter(mp);
 118
 119         /* No more waiters a different mutex could be used */
 120         if (atomic_dec_and_test(&cvp->cv_waiters)) {
 121                 cvp->cv_mutex = NULL;
 122                 wake_up(&cvp->cv_destroy);
 123         }
 124
 125         finish_wait(&cvp->cv_event, &wait);
 126
 127         SEXIT;
 128 }
 129
 130 void
 131 __cv_wait(kcondvar_t *cvp, kmutex_t *mp)
 132 {
 133         cv_wait_common(cvp, mp, TASK_UNINTERRUPTIBLE);
 134 }
 135 EXPORT_SYMBOL(__cv_wait);
 136
 137 void
 138 __cv_wait_interruptible(kcondvar_t *cvp, kmutex_t *mp)
 139 {
 140         cv_wait_common(cvp, mp, TASK_INTERRUPTIBLE);
 141 }
 142 EXPORT_SYMBOL(__cv_wait_interruptible);
 143
 144 /* 'expire_time' argument is an absolute wall clock time in jiffies.
 145  * Return value is time left (expire_time - now) or -1 if timeout occurred.
 146  */
 147 static clock_t
 148 __cv_timedwait_common(kcondvar_t *cvp, kmutex_t *mp,
 149                       clock_t expire_time, int state)
 150 {
 151         DEFINE_WAIT(wait);
 152         clock_t time_left;
 153         SENTRY;
 154
 155         ASSERT(cvp);
 156         ASSERT(mp);
 157         ASSERT(cvp->cv_magic == CV_MAGIC);
 158         ASSERT(mutex_owned(mp));
 159
 160         if (cvp->cv_mutex == NULL)
 161                 cvp->cv_mutex = mp;
 162
 163         /* Ensure the same mutex is used by all callers */
 164         ASSERT(cvp->cv_mutex == mp);
 165
 166         /* XXX - Does not handle jiffie wrap properly */
 167         time_left = expire_time - jiffies;
 168         if (time_left <= 0)
 169                 SRETURN(-1);
 170
 171         prepare_to_wait_exclusive(&cvp->cv_event, &wait, state);
 172         atomic_inc(&cvp->cv_waiters);
 173
 174         /* Mutex should be dropped after prepare_to_wait() this
 175          * ensures we're linked in to the waiters list and avoids the
 176          * race where 'cvp->cv_waiters > 0' but the list is empty. */
 177         mutex_exit(mp);
 178         time_left = schedule_timeout(time_left);
 179         mutex_enter(mp);
 180
 181         /* No more waiters a different mutex could be used */
 182         if (atomic_dec_and_test(&cvp->cv_waiters)) {
 183                 cvp->cv_mutex = NULL;
 184                 wake_up(&cvp->cv_destroy);
 185         }
 186
 187         finish_wait(&cvp->cv_event, &wait);
 188
 189         SRETURN(time_left > 0 ? time_left : -1);
 190 }
 191
 192 clock_t
 193 __cv_timedwait(kcondvar_t *cvp, kmutex_t *mp, clock_t exp_time)
 194 {
 195         return __cv_timedwait_common(cvp, mp, exp_time, TASK_UNINTERRUPTIBLE);
 196 }
 197 EXPORT_SYMBOL(__cv_timedwait);
 198
 199 clock_t
 200 __cv_timedwait_interruptible(kcondvar_t *cvp, kmutex_t *mp, clock_t exp_time)
 201 {
 202         return __cv_timedwait_common(cvp, mp, exp_time, TASK_INTERRUPTIBLE);
 203 }
 204 EXPORT_SYMBOL(__cv_timedwait_interruptible);
 205
 206 void
 207 __cv_signal(kcondvar_t *cvp)
 208 {
 209         SENTRY;
 210         ASSERT(cvp);
 211         ASSERT(cvp->cv_magic == CV_MAGIC);
 212
 213         /* All waiters are added with WQ_FLAG_EXCLUSIVE so only one
 214          * waiter will be set runable with each call to wake_up().
 215          * Additionally wake_up() holds a spin_lock assoicated with
 216          * the wait queue to ensure we don't race waking up processes. */
 217         if (atomic_read(&cvp->cv_waiters) > 0)
 218                 wake_up(&cvp->cv_event);
 219
 220         SEXIT;
 221 }
 222 EXPORT_SYMBOL(__cv_signal);
 223
 224 void
 225 __cv_broadcast(kcondvar_t *cvp)
 226 {
 227         ASSERT(cvp);
 228         ASSERT(cvp->cv_magic == CV_MAGIC);
 229         SENTRY;
 230
 231         /* Wake_up_all() will wake up all waiters even those which
 232          * have the WQ_FLAG_EXCLUSIVE flag set. */
 233         if (atomic_read(&cvp->cv_waiters) > 0)
 234                 wake_up_all(&cvp->cv_event);
 235
 236         SEXIT;
 237 }
 238 EXPORT_SYMBOL(__cv_broadcast);