1 /* sem_wait -- wait on a semaphore. Generic futex-using version.
2 Copyright (C) 2003-2015 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Paul Mackerras <paulus@au.ibm.com>, 2003.
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 2.1 of the License, or (at your option) any later version.
11 The GNU C Library is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, see
18 <http://www.gnu.org/licenses/>. */
22 #include <lowlevellock.h>
23 #include <internaltypes.h>
24 #include <semaphore.h>
27 #include <shlib-compat.h>
33 __sem_wait_cleanup (void *arg)
35 struct new_sem *isem = (struct new_sem *) arg;
37 atomic_decrement (&isem->nwaiters);
40 /* This is in a seperate function in order to make sure gcc
41 puts the call site into an exception region, and thus the
42 cleanups get properly run. */
44 __attribute__ ((noinline))
45 do_futex_wait (struct new_sem *isem)
47 int err, oldtype = __pthread_enable_asynccancel ();
49 err = lll_futex_wait (&isem->value, 0, isem->private ^ FUTEX_PRIVATE_FLAG);
51 __pthread_disable_asynccancel (oldtype);
56 __new_sem_wait (sem_t *sem)
58 struct new_sem *isem = (struct new_sem *) sem;
61 if (atomic_decrement_if_positive (&isem->value) > 0)
64 atomic_increment (&isem->nwaiters);
66 pthread_cleanup_push (__sem_wait_cleanup, isem);
70 err = do_futex_wait(isem);
71 if (err != 0 && err != -EWOULDBLOCK)
78 if (atomic_decrement_if_positive (&isem->value) > 0)
85 pthread_cleanup_pop (0);
87 atomic_decrement (&isem->nwaiters);
91 versioned_symbol (libpthread, __new_sem_wait, sem_wait, GLIBC_2_1);
94 #if SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_1)
96 attribute_compat_text_section
97 __old_sem_wait (sem_t *sem)
99 int *futex = (int *) sem;
104 if (atomic_decrement_if_positive (futex) > 0)
107 /* Enable asynchronous cancellation. Required by the standard. */
108 int oldtype = __pthread_enable_asynccancel ();
110 /* Always assume the semaphore is shared. */
111 err = lll_futex_wait (futex, 0, LLL_SHARED);
113 /* Disable asynchronous cancellation. */
114 __pthread_disable_asynccancel (oldtype);
116 while (err == 0 || err == -EWOULDBLOCK);
122 compat_symbol (libpthread, __old_sem_wait, sem_wait, GLIBC_2_0);