/share/man/man3/pthread_rwlock_timedrdlock.3

https://bitbucket.org/freebsd/freebsd-head/ · Unknown · 118 lines · 118 code · 0 blank · 0 comment · 0 complexity · 910b6d3bbc84495d4f54a8ab62fc0def MD5 · raw file 

    

  1. .\" Copyright (c) 2004 Michael Telahun Makonnen
    2. 

  2. .\" All rights reserved.
    3. 

  3. .\"
    4. 

  4. .\" Redistribution and use in source and binary forms, with or without
    5. 

  5. .\" modification, are permitted provided that the following conditions
    6. 

  6. .\" are met:
    7. 

  7. .\" 1. Redistributions of source code must retain the above copyright
    8. 

  8. .\"    notice, this list of conditions and the following disclaimer.
    9. 

  9. .\" 2. Redistributions in binary form must reproduce the above copyright
    10. 

  10. .\"    notice, this list of conditions and the following disclaimer in the
    11. 

  11. .\"    documentation and/or other materials provided with the distribution.
    12. 

  12. .\"
    13. 

  13. .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
    14. 

  14. .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
    15. 

  15. .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
    16. 

  16. .\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
    17. 

  17. .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
    18. 

  18. .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
    19. 

  19. .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
    20. 

  20. .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
    21. 

  21. .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
    22. 

  22. .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
    23. 

  23. .\" SUCH DAMAGE.
    24. 

  24. .\"
    25. 

  25. .\" $FreeBSD$
    26. 

  26. .\"
    27. 

  27. .Dd January 16, 2004
    28. 

  28. .Dt PTHREAD_RWLOCK_TIMEDRDLOCK 3
    29. 

  29. .Os
    30. 

  30. .Sh NAME
    31. 

  31. .Nm pthread_rwlock_timedrdlock
    32. 

  32. .Nd "acquire a read-write lock for reading or give up after a specified period"
    33. 

  33. .Sh LIBRARY
    34. 

  34. .Lb libpthread
    35. 

  35. .Sh SYNOPSIS
    36. 

  36. .In pthread.h
    37. 

  37. .Ft int
    38. 

  38. .Fn pthread_rwlock_timedrdlock "pthread_rwlock_t *rwlock" "const struct timespec *abs_timeout"
    39. 

  39. .Sh DESCRIPTION
    40. 

  40. This function acquires a read lock on the read-write lock
    41. 

  41. .Fa rwlock .
    42. 

  42. However, if the lock cannot be
    43. 

  43. acquired without waiting for another thread to
    44. 

  44. unlock the lock,
    45. 

  45. this wait shall be terminated when
    46. 

  46. .Fa abs_timeout
    47. 

  47. expires.
    48. 

  48. .Pp
    49. 

  49. A thread may hold multiple concurrent read locks.
    50. 

  50. The
    51. 

  51. .Xr pthread_rwlock_unlock 3
    52. 

  52. function must be called once for each lock acquired.
    53. 

  53. .Pp
    54. 

  54. If the thread should be interrupted by a signal,
    55. 

  55. the
    56. 

  56. .Fn pthread_rwlock_timedrdlock
    57. 

  57. function will be automatically restarted after the thread returns from
    58. 

  58. the signal handler.
    59. 

  59. .Pp
    60. 

  60. The calling thread may deadlock if
    61. 

  61. at the time the call is made it holds a write lock on
    62. 

  62. .Fa rwlock .
    63. 

  63. The results are undefined if this function is called with
    64. 

  64. an uninitialized read-write lock.
    65. 

  65. .Sh IMPLEMENTATION NOTES
    66. 

  66. To prevent writer starvation, writers are favored over readers.
    67. 

  67. .Sh RETURN VALUES
    68. 

  68. If successful, the
    69. 

  69. .Fn pthread_rwlock_timedrdlock
    70. 

  70. function will return zero.
    71. 

  71. Otherwise, an error number will be returned to indicate the error.
    72. 

  72. .Pp
    73. 

  73. This function shall not return an error code of
    74. 

  74. .Er EINTR .
    75. 

  75. .Sh ERRORS
    76. 

  76. The
    77. 

  77. .Fn pthread_rwlock_timedrdlock
    78. 

  78. function will fail if:
    79. 

  79. .Bl -tag -width Er
    80. 

  80. .It Bq Er ETIMEDOUT
    81. 

  81. The lock could not be acquired before the specified timeout expired.
    82. 

  82. .El
    83. 

  83. .Pp
    84. 

  84. The
    85. 

  85. .Fn pthread_rwlock_timedrdlock
    86. 

  86. function may fail if:
    87. 

  87. .Bl -tag -width Er
    88. 

  88. .It Bq Er EAGAIN
    89. 

  89. The read lock could not be
    90. 

  90. acquired because the maximum number of read locks for
    91. 

  91. .Fa rwlock
    92. 

  92. would be exceeded.
    93. 

  93. .It Bq Er EDEADLK
    94. 

  94. The calling thread already holds a write lock on
    95. 

  95. .Fa rwlock .
    96. 

  96. .It Bq Er EINVAL
    97. 

  97. The value specified by
    98. 

  98. .Fa rwlock
    99. 

  99. does not refer to an initialized read-write lock object,
    100. 

  100. or the
    101. 

  101. .Fa abs_timeout
    102. 

  102. nanosecond value is less than zero or
    103. 

  103. greater than or equal to 1 billion.
    104. 

  104. .El
    105. 

  105. .Sh SEE ALSO
    106. 

  106. .Xr pthread_rwlock_init 3 ,
    107. 

  107. .Xr pthread_rwlock_timedwrlock 3 ,
    108. 

  108. .Xr pthread_rwlock_unlock 3
    109. 

  109. .Sh STANDARDS
    110. 

  110. The
    111. 

  111. .Fn pthread_rwlock_timedrdlock
    112. 

  112. function is expected to conform to
    113. 

  113. .St -p1003.1-96 .
    114. 

  114. .Sh HISTORY
    115. 

  115. The
    116. 

  116. .Fn pthread_rwlock_timedrdlock
    117. 

  117. function first appeared in
    118. 

  118. .Fx 5.2 .
    119.