sysdeps/htl/pt-rwlock-timedwrlock.c

   1 /* Acquire a rwlock for writing.  Generic version.
   2    Copyright (C) 2002-2023 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library;  if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <pthread.h>
  20 #include <assert.h>
  21 #include <time.h>
  22
  23 #include <pt-internal.h>
  24
  25 /* Acquire RWLOCK for writing blocking until *ABSTIME if we cannot get
  26    it.  As a special GNU extension, if ABSTIME is NULL then the wait
  27    shall not time out.  */
  28 int
  29 __pthread_rwlock_timedwrlock_internal (struct __pthread_rwlock *rwlock,
  30                                        clockid_t clockid,
  31                                        const struct timespec *abstime)
  32 {
  33   error_t err;
  34   int drain;
  35   struct __pthread *self;
  36
  37   __pthread_spin_wait (&rwlock->__lock);
  38   if (__pthread_spin_trylock (&rwlock->__held) == 0)
  39     /* Successfully acquired the lock.  */
  40     {
  41       assert (rwlock->__readerqueue == 0);
  42       assert (rwlock->__writerqueue == 0);
  43       assert (rwlock->__readers == 0);
  44
  45       __pthread_spin_unlock (&rwlock->__lock);
  46       return 0;
  47     }
  48
  49   /* The lock is busy.  */
  50
  51   if (abstime != NULL && ! valid_nanoseconds (abstime->tv_nsec))
  52     {
  53       __pthread_spin_unlock (&rwlock->__lock);
  54       return EINVAL;
  55     }
  56
  57   self = _pthread_self ();
  58
  59   /* Add ourselves to the queue.  */
  60   __pthread_enqueue (&rwlock->__writerqueue, self);
  61   __pthread_spin_unlock (&rwlock->__lock);
  62
  63   /* Block the thread.  */
  64   if (abstime != NULL)
  65     err = __pthread_timedblock (self, abstime, clockid);
  66   else
  67     {
  68       err = 0;
  69       __pthread_block (self);
  70     }
  71
  72   __pthread_spin_wait (&rwlock->__lock);
  73   if (self->prevp == NULL)
  74     /* Another thread removed us from the queue, which means a wakeup message
  75        has been sent.  It was either consumed while we were blocking, or
  76        queued after we timed out and before we acquired the rwlock lock, in
  77        which case the message queue must be drained.  */
  78     drain = err ? 1 : 0;
  79   else
  80     {
  81       /* We're still in the queue.  Noone attempted to wake us up, i.e. we
  82          timed out.  */
  83       __pthread_dequeue (self);
  84       drain = 0;
  85     }
  86   __pthread_spin_unlock (&rwlock->__lock);
  87
  88   if (drain)
  89     __pthread_block (self);
  90
  91   if (err)
  92     {
  93       assert (err == ETIMEDOUT);
  94       return err;
  95     }
  96
  97   assert (rwlock->__readers == 0);
  98
  99   return 0;
 100 }
 101
 102 int
 103 __pthread_rwlock_timedwrlock (struct __pthread_rwlock *rwlock,
 104                               const struct timespec *abstime)
 105 {
 106   return __pthread_rwlock_timedwrlock_internal (rwlock, CLOCK_REALTIME, abstime);
 107 }
 108 weak_alias (__pthread_rwlock_timedwrlock, pthread_rwlock_timedwrlock)
 109
 110 int
 111 __pthread_rwlock_clockwrlock (struct __pthread_rwlock *rwlock,
 112                               clockid_t clockid,
 113                               const struct timespec *abstime)
 114 {
 115   return __pthread_rwlock_timedwrlock_internal (rwlock, clockid, abstime);
 116 }
 117 weak_alias (__pthread_rwlock_clockwrlock, pthread_rwlock_clockwrlock)