1 /* Copyright (C) 2003, 2004 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, write to the Free
17 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
23 #include <lowlevellock.h>
27 #include <shlib-compat.h>
30 struct _condvar_cleanup_buffer
34 pthread_mutex_t
*mutex
;
40 __attribute__ ((visibility ("hidden")))
41 __condvar_cleanup (void *arg
)
43 struct _condvar_cleanup_buffer
*cbuffer
=
44 (struct _condvar_cleanup_buffer
*) arg
;
45 unsigned int destroying
;
47 /* We are going to modify shared data. */
48 lll_mutex_lock (cbuffer
->cond
->__data
.__lock
);
50 if (cbuffer
->bc_seq
== cbuffer
->cond
->__data
.__broadcast_seq
)
52 /* This thread is not waiting anymore. Adjust the sequence counters
54 ++cbuffer
->cond
->__data
.__wakeup_seq
;
55 ++cbuffer
->cond
->__data
.__woken_seq
;
56 ++cbuffer
->cond
->__data
.__futex
;
59 cbuffer
->cond
->__data
.__nwaiters
-= 1 << COND_CLOCK_BITS
;
61 /* If pthread_cond_destroy was called on this variable already,
62 notify the pthread_cond_destroy caller all waiters have left
63 and it can be successfully destroyed. */
65 if (cbuffer
->cond
->__data
.__total_seq
== -1ULL
66 && cbuffer
->cond
->__data
.__nwaiters
< (1 << COND_CLOCK_BITS
))
68 lll_futex_wake (&cbuffer
->cond
->__data
.__nwaiters
, 1);
73 lll_mutex_unlock (cbuffer
->cond
->__data
.__lock
);
75 /* Wake everybody to make sure no condvar signal gets lost. */
77 lll_futex_wake (&cbuffer
->cond
->__data
.__futex
, INT_MAX
);
79 /* Get the mutex before returning unless asynchronous cancellation
81 __pthread_mutex_cond_lock (cbuffer
->mutex
);
86 __pthread_cond_wait (cond
, mutex
)
88 pthread_mutex_t
*mutex
;
90 struct _pthread_cleanup_buffer buffer
;
91 struct _condvar_cleanup_buffer cbuffer
;
94 /* Make sure we are along. */
95 lll_mutex_lock (cond
->__data
.__lock
);
97 /* Now we can release the mutex. */
98 err
= __pthread_mutex_unlock_usercnt (mutex
, 0);
99 if (__builtin_expect (err
, 0))
101 lll_mutex_unlock (cond
->__data
.__lock
);
105 /* We have one new user of the condvar. */
106 ++cond
->__data
.__total_seq
;
107 ++cond
->__data
.__futex
;
108 cond
->__data
.__nwaiters
+= 1 << COND_CLOCK_BITS
;
110 /* Remember the mutex we are using here. If there is already a
111 different address store this is a bad user bug. Do not store
112 anything for pshared condvars. */
113 if (cond
->__data
.__mutex
!= (void *) ~0l)
114 cond
->__data
.__mutex
= mutex
;
116 /* Prepare structure passed to cancellation handler. */
118 cbuffer
.mutex
= mutex
;
120 /* Before we block we enable cancellation. Therefore we have to
121 install a cancellation handler. */
122 __pthread_cleanup_push (&buffer
, __condvar_cleanup
, &cbuffer
);
124 /* The current values of the wakeup counter. The "woken" counter
125 must exceed this value. */
126 unsigned long long int val
;
127 unsigned long long int seq
;
128 val
= seq
= cond
->__data
.__wakeup_seq
;
129 /* Remember the broadcast counter. */
130 cbuffer
.bc_seq
= cond
->__data
.__broadcast_seq
;
134 unsigned int futex_val
= cond
->__data
.__futex
;
136 /* Prepare to wait. Release the condvar futex. */
137 lll_mutex_unlock (cond
->__data
.__lock
);
139 /* Enable asynchronous cancellation. Required by the standard. */
140 cbuffer
.oldtype
= __pthread_enable_asynccancel ();
142 /* Wait until woken by signal or broadcast. */
143 lll_futex_wait (&cond
->__data
.__futex
, futex_val
);
145 /* Disable asynchronous cancellation. */
146 __pthread_disable_asynccancel (cbuffer
.oldtype
);
148 /* We are going to look at shared data again, so get the lock. */
149 lll_mutex_lock (cond
->__data
.__lock
);
151 /* If a broadcast happened, we are done. */
152 if (cbuffer
.bc_seq
!= cond
->__data
.__broadcast_seq
)
155 /* Check whether we are eligible for wakeup. */
156 val
= cond
->__data
.__wakeup_seq
;
158 while (val
== seq
|| cond
->__data
.__woken_seq
== val
);
160 /* Another thread woken up. */
161 ++cond
->__data
.__woken_seq
;
165 cond
->__data
.__nwaiters
-= 1 << COND_CLOCK_BITS
;
167 /* If pthread_cond_destroy was called on this varaible already,
168 notify the pthread_cond_destroy caller all waiters have left
169 and it can be successfully destroyed. */
170 if (cond
->__data
.__total_seq
== -1ULL
171 && cond
->__data
.__nwaiters
< (1 << COND_CLOCK_BITS
))
172 lll_futex_wake (&cond
->__data
.__nwaiters
, 1);
174 /* We are done with the condvar. */
175 lll_mutex_unlock (cond
->__data
.__lock
);
177 /* The cancellation handling is back to normal, remove the handler. */
178 __pthread_cleanup_pop (&buffer
, 0);
180 /* Get the mutex before returning. */
181 return __pthread_mutex_cond_lock (mutex
);
184 versioned_symbol (libpthread
, __pthread_cond_wait
, pthread_cond_wait
,