Remove shlib-versions entries redundant with DEFAULT entries.
[glibc.git] / nptl / pthread_rwlock_timedrdlock.c
blob340ae3d3941c241b6b0740e550887f9757b4cede
1 /* Copyright (C) 2003-2014 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3 Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>, 2003.
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.
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.
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 <http://www.gnu.org/licenses/>. */
19 #include <errno.h>
20 #include <sysdep.h>
21 #include <lowlevellock.h>
22 #include <pthread.h>
23 #include <pthreadP.h>
24 #include <kernel-features.h>
27 /* Try to acquire read lock for RWLOCK or return after specfied time. */
28 int
29 pthread_rwlock_timedrdlock (rwlock, abstime)
30 pthread_rwlock_t *rwlock;
31 const struct timespec *abstime;
33 int result = 0;
35 /* Make sure we are alone. */
36 lll_lock(rwlock->__data.__lock, rwlock->__data.__shared);
38 while (1)
40 int err;
42 /* Get the rwlock if there is no writer... */
43 if (rwlock->__data.__writer == 0
44 /* ...and if either no writer is waiting or we prefer readers. */
45 && (!rwlock->__data.__nr_writers_queued
46 || PTHREAD_RWLOCK_PREFER_READER_P (rwlock)))
48 /* Increment the reader counter. Avoid overflow. */
49 if (++rwlock->__data.__nr_readers == 0)
51 /* Overflow on number of readers. */
52 --rwlock->__data.__nr_readers;
53 result = EAGAIN;
56 break;
59 /* Make sure we are not holding the rwlock as a writer. This is
60 a deadlock situation we recognize and report. */
61 if (__builtin_expect (rwlock->__data.__writer
62 == THREAD_GETMEM (THREAD_SELF, tid), 0))
64 result = EDEADLK;
65 break;
68 /* Make sure the passed in timeout value is valid. Ideally this
69 test would be executed once. But since it must not be
70 performed if we would not block at all simply moving the test
71 to the front is no option. Replicating all the code is
72 costly while this test is not. */
73 if (__builtin_expect (abstime->tv_nsec >= 1000000000
74 || abstime->tv_nsec < 0, 0))
76 result = EINVAL;
77 break;
80 /* Work around the fact that the kernel rejects negative timeout values
81 despite them being valid. */
82 if (__glibc_unlikely (abstime->tv_sec < 0))
84 result = ETIMEDOUT;
85 break;
88 #if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
89 || !defined lll_futex_timed_wait_bitset)
90 /* Get the current time. So far we support only one clock. */
91 struct timeval tv;
92 (void) gettimeofday (&tv, NULL);
94 /* Convert the absolute timeout value to a relative timeout. */
95 struct timespec rt;
96 rt.tv_sec = abstime->tv_sec - tv.tv_sec;
97 rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000;
98 if (rt.tv_nsec < 0)
100 rt.tv_nsec += 1000000000;
101 --rt.tv_sec;
103 /* Did we already time out? */
104 if (rt.tv_sec < 0)
106 /* Yep, return with an appropriate error. */
107 result = ETIMEDOUT;
108 break;
110 #endif
112 /* Remember that we are a reader. */
113 if (++rwlock->__data.__nr_readers_queued == 0)
115 /* Overflow on number of queued readers. */
116 --rwlock->__data.__nr_readers_queued;
117 result = EAGAIN;
118 break;
121 int waitval = rwlock->__data.__readers_wakeup;
123 /* Free the lock. */
124 lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
126 /* Wait for the writer to finish. */
127 #if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
128 || !defined lll_futex_timed_wait_bitset)
129 err = lll_futex_timed_wait (&rwlock->__data.__readers_wakeup,
130 waitval, &rt, rwlock->__data.__shared);
131 #else
132 err = lll_futex_timed_wait_bitset (&rwlock->__data.__readers_wakeup,
133 waitval, abstime,
134 FUTEX_CLOCK_REALTIME,
135 rwlock->__data.__shared);
136 #endif
138 /* Get the lock. */
139 lll_lock (rwlock->__data.__lock, rwlock->__data.__shared);
141 --rwlock->__data.__nr_readers_queued;
143 /* Did the futex call time out? */
144 if (err == -ETIMEDOUT)
146 /* Yep, report it. */
147 result = ETIMEDOUT;
148 break;
152 /* We are done, free the lock. */
153 lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
155 return result;