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