1 /* Copyright (C) 2003-2015 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 <stap-probe.h>
28 /* Acquire write lock for RWLOCK. */
29 static int __attribute__((noinline
))
30 __pthread_rwlock_wrlock_slow (pthread_rwlock_t
*rwlock
)
34 /* Caller has taken the lock. */
38 /* Make sure we are not holding the rwlock as a writer. This is
39 a deadlock situation we recognize and report. */
40 if (__builtin_expect (rwlock
->__data
.__writer
41 == THREAD_GETMEM (THREAD_SELF
, tid
), 0))
47 /* Remember that we are a writer. */
48 if (++rwlock
->__data
.__nr_writers_queued
== 0)
50 /* Overflow on number of queued writers. */
51 --rwlock
->__data
.__nr_writers_queued
;
56 int waitval
= rwlock
->__data
.__writer_wakeup
;
59 lll_unlock (rwlock
->__data
.__lock
, rwlock
->__data
.__shared
);
61 /* Wait for the writer or reader(s) to finish. */
62 lll_futex_wait (&rwlock
->__data
.__writer_wakeup
, waitval
,
63 rwlock
->__data
.__shared
);
66 lll_lock (rwlock
->__data
.__lock
, rwlock
->__data
.__shared
);
68 /* To start over again, remove the thread from the writer list. */
69 --rwlock
->__data
.__nr_writers_queued
;
71 /* Get the rwlock if there is no writer and no reader. */
72 if (rwlock
->__data
.__writer
== 0 && rwlock
->__data
.__nr_readers
== 0)
74 /* Mark self as writer. */
75 rwlock
->__data
.__writer
= THREAD_GETMEM (THREAD_SELF
, tid
);
77 LIBC_PROBE (wrlock_acquire_write
, 1, rwlock
);
82 /* We are done, free the lock. */
83 lll_unlock (rwlock
->__data
.__lock
, rwlock
->__data
.__shared
);
88 /* Fast path of acquiring write lock for RWLOCK. */
91 __pthread_rwlock_wrlock (pthread_rwlock_t
*rwlock
)
93 LIBC_PROBE (wrlock_entry
, 1, rwlock
);
95 if (ELIDE_LOCK (rwlock
->__data
.__rwelision
,
96 rwlock
->__data
.__lock
== 0
97 && rwlock
->__data
.__writer
== 0
98 && rwlock
->__data
.__nr_readers
== 0))
101 /* Make sure we are alone. */
102 lll_lock (rwlock
->__data
.__lock
, rwlock
->__data
.__shared
);
104 /* Get the rwlock if there is no writer and no reader. */
105 if (__glibc_likely((rwlock
->__data
.__writer
|
106 rwlock
->__data
.__nr_readers
) == 0))
108 /* Mark self as writer. */
109 rwlock
->__data
.__writer
= THREAD_GETMEM (THREAD_SELF
, tid
);
111 LIBC_PROBE (wrlock_acquire_write
, 1, rwlock
);
113 /* We are done, free the lock. */
114 lll_unlock (rwlock
->__data
.__lock
, rwlock
->__data
.__shared
);
119 return __pthread_rwlock_wrlock_slow (rwlock
);
123 weak_alias (__pthread_rwlock_wrlock
, pthread_rwlock_wrlock
)
124 hidden_def (__pthread_rwlock_wrlock
)