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)
 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         schedule();
 125         mutex_enter(mp);
 126
 127         /* No more waiters a different mutex could be used */
 128         if (atomic_dec_and_test(&cvp->cv_waiters)) {
 129                 cvp->cv_mutex = NULL;
 130                 wake_up(&cvp->cv_destroy);
 131         }
 132
 133         finish_wait(&cvp->cv_event, &wait);
 134         atomic_dec(&cvp->cv_refs);
 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         atomic_inc(&cvp->cv_refs);
 169
 170         if (cvp->cv_mutex == NULL)
 171                 cvp->cv_mutex = mp;
 172
 173         /* Ensure the same mutex is used by all callers */
 174         ASSERT(cvp->cv_mutex == mp);
 175
 176         /* XXX - Does not handle jiffie wrap properly */
 177         time_left = expire_time - jiffies;
 178         if (time_left <= 0) {
 179                 atomic_dec(&cvp->cv_refs);
 180                 SRETURN(-1);
 181         }
 182
 183         prepare_to_wait_exclusive(&cvp->cv_event, &wait, state);
 184         atomic_inc(&cvp->cv_waiters);
 185
 186         /* Mutex should be dropped after prepare_to_wait() this
 187          * ensures we're linked in to the waiters list and avoids the
 188          * race where 'cvp->cv_waiters > 0' but the list is empty. */
 189         mutex_exit(mp);
 190         time_left = schedule_timeout(time_left);
 191         mutex_enter(mp);
 192
 193         /* No more waiters a different mutex could be used */
 194         if (atomic_dec_and_test(&cvp->cv_waiters)) {
 195                 cvp->cv_mutex = NULL;
 196                 wake_up(&cvp->cv_destroy);
 197         }
 198
 199         finish_wait(&cvp->cv_event, &wait);
 200         atomic_dec(&cvp->cv_refs);
 201
 202         SRETURN(time_left > 0 ? time_left : -1);
 203 }
 204
 205 clock_t
 206 __cv_timedwait(kcondvar_t *cvp, kmutex_t *mp, clock_t exp_time)
 207 {
 208         return __cv_timedwait_common(cvp, mp, exp_time, TASK_UNINTERRUPTIBLE);
 209 }
 210 EXPORT_SYMBOL(__cv_timedwait);
 211
 212 clock_t
 213 __cv_timedwait_interruptible(kcondvar_t *cvp, kmutex_t *mp, clock_t exp_time)
 214 {
 215         return __cv_timedwait_common(cvp, mp, exp_time, TASK_INTERRUPTIBLE);
 216 }
 217 EXPORT_SYMBOL(__cv_timedwait_interruptible);
 218
 219 void
 220 __cv_signal(kcondvar_t *cvp)
 221 {
 222         SENTRY;
 223         ASSERT(cvp);
 224         ASSERT(cvp->cv_magic == CV_MAGIC);
 225         atomic_inc(&cvp->cv_refs);
 226
 227         /* All waiters are added with WQ_FLAG_EXCLUSIVE so only one
 228          * waiter will be set runable with each call to wake_up().
 229          * Additionally wake_up() holds a spin_lock assoicated with
 230          * the wait queue to ensure we don't race waking up processes. */
 231         if (atomic_read(&cvp->cv_waiters) > 0)
 232                 wake_up(&cvp->cv_event);
 233
 234         atomic_dec(&cvp->cv_refs);
 235         SEXIT;
 236 }
 237 EXPORT_SYMBOL(__cv_signal);
 238
 239 void
 240 __cv_broadcast(kcondvar_t *cvp)
 241 {
 242         SENTRY;
 243         ASSERT(cvp);
 244         ASSERT(cvp->cv_magic == CV_MAGIC);
 245         atomic_inc(&cvp->cv_refs);
 246
 247         /* Wake_up_all() will wake up all waiters even those which
 248          * have the WQ_FLAG_EXCLUSIVE flag set. */
 249         if (atomic_read(&cvp->cv_waiters) > 0)
 250                 wake_up_all(&cvp->cv_event);
 251
 252         atomic_dec(&cvp->cv_refs);
 253         SEXIT;
 254 }
 255 EXPORT_SYMBOL(__cv_broadcast);