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/>. */
21 #include <lowlevellock.h>
24 #include <kernel-features.h>
27 /* Try to acquire write lock for RWLOCK or return after specfied time. */
29 pthread_rwlock_timedwrlock (rwlock
, abstime
)
30 pthread_rwlock_t
*rwlock
;
31 const struct timespec
*abstime
;
35 /* Make sure we are alone. */
36 lll_lock (rwlock
->__data
.__lock
, rwlock
->__data
.__shared
);
42 /* Get the rwlock if there is no writer and no reader. */
43 if (rwlock
->__data
.__writer
== 0 && rwlock
->__data
.__nr_readers
== 0)
45 /* Mark self as writer. */
46 rwlock
->__data
.__writer
= THREAD_GETMEM (THREAD_SELF
, tid
);
50 /* Make sure we are not holding the rwlock as a writer. This is
51 a deadlock situation we recognize and report. */
52 if (__builtin_expect (rwlock
->__data
.__writer
53 == THREAD_GETMEM (THREAD_SELF
, tid
), 0))
59 /* Make sure the passed in timeout value is valid. Ideally this
60 test would be executed once. But since it must not be
61 performed if we would not block at all simply moving the test
62 to the front is no option. Replicating all the code is
63 costly while this test is not. */
64 if (__builtin_expect (abstime
->tv_nsec
>= 1000000000
65 || abstime
->tv_nsec
< 0, 0))
71 /* Work around the fact that the kernel rejects negative timeout values
72 despite them being valid. */
73 if (__glibc_unlikely (abstime
->tv_sec
< 0))
79 #if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
80 || !defined lll_futex_timed_wait_bitset)
81 /* Get the current time. So far we support only one clock. */
83 (void) gettimeofday (&tv
, NULL
);
85 /* Convert the absolute timeout value to a relative timeout. */
87 rt
.tv_sec
= abstime
->tv_sec
- tv
.tv_sec
;
88 rt
.tv_nsec
= abstime
->tv_nsec
- tv
.tv_usec
* 1000;
91 rt
.tv_nsec
+= 1000000000;
94 /* Did we already time out? */
102 /* Remember that we are a writer. */
103 if (++rwlock
->__data
.__nr_writers_queued
== 0)
105 /* Overflow on number of queued writers. */
106 --rwlock
->__data
.__nr_writers_queued
;
111 int waitval
= rwlock
->__data
.__writer_wakeup
;
114 lll_unlock (rwlock
->__data
.__lock
, rwlock
->__data
.__shared
);
116 /* Wait for the writer or reader(s) to finish. */
117 #if (!defined __ASSUME_FUTEX_CLOCK_REALTIME \
118 || !defined lll_futex_timed_wait_bitset)
119 err
= lll_futex_timed_wait (&rwlock
->__data
.__writer_wakeup
,
120 waitval
, &rt
, rwlock
->__data
.__shared
);
122 err
= lll_futex_timed_wait_bitset (&rwlock
->__data
.__writer_wakeup
,
124 FUTEX_CLOCK_REALTIME
,
125 rwlock
->__data
.__shared
);
129 lll_lock (rwlock
->__data
.__lock
, rwlock
->__data
.__shared
);
131 /* To start over again, remove the thread from the writer list. */
132 --rwlock
->__data
.__nr_writers_queued
;
134 /* Did the futex call time out? */
135 if (err
== -ETIMEDOUT
)
142 /* We are done, free the lock. */
143 lll_unlock (rwlock
->__data
.__lock
, rwlock
->__data
.__shared
);