]>
Commit | Line | Data |
---|---|---|
04277e02 | 1 | /* Copyright (C) 2002-2019 Free Software Foundation, Inc. |
76a50749 UD |
2 | This file is part of the GNU C Library. |
3 | Contributed by Ulrich Drepper <drepper@redhat.com>, 2002. | |
4 | ||
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. | |
9 | ||
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. | |
14 | ||
15 | You should have received a copy of the GNU Lesser General Public | |
59ba27a6 | 16 | License along with the GNU C Library; if not, see |
5a82c748 | 17 | <https://www.gnu.org/licenses/>. */ |
76a50749 | 18 | |
73f7c32c | 19 | #include <errno.h> |
bf293afe | 20 | #include <shlib-compat.h> |
76a50749 | 21 | #include "pthreadP.h" |
5acf7263 | 22 | #include <stap-probe.h> |
ed19993b TR |
23 | #include <atomic.h> |
24 | #include <futex-internal.h> | |
25 | ||
26 | #include "pthread_cond_common.c" | |
27 | ||
28 | /* See __pthread_cond_wait for a high-level description of the algorithm. | |
29 | ||
30 | A correct program must make sure that no waiters are blocked on the condvar | |
31 | when it is destroyed, and that there are no concurrent signals or | |
32 | broadcasts. To wake waiters reliably, the program must signal or | |
33 | broadcast while holding the mutex or after having held the mutex. It must | |
34 | also ensure that no signal or broadcast are still pending to unblock | |
35 | waiters; IOW, because waiters can wake up spuriously, the program must | |
36 | effectively ensure that destruction happens after the execution of those | |
37 | signal or broadcast calls. | |
38 | Thus, we can assume that all waiters that are still accessing the condvar | |
39 | have been woken. We wait until they have confirmed to have woken up by | |
40 | decrementing __wrefs. */ | |
76a50749 | 41 | int |
9d46370c | 42 | __pthread_cond_destroy (pthread_cond_t *cond) |
76a50749 | 43 | { |
5acf7263 RM |
44 | LIBC_PROBE (cond_destroy, 1, cond); |
45 | ||
ed19993b TR |
46 | /* Set the wake request flag. We could also spin, but destruction that is |
47 | concurrent with still-active waiters is probably neither common nor | |
48 | performance critical. Acquire MO to synchronize with waiters confirming | |
49 | that they finished. */ | |
50 | unsigned int wrefs = atomic_fetch_or_acquire (&cond->__data.__wrefs, 4); | |
51 | int private = __condvar_get_private (wrefs); | |
52 | while (wrefs >> 3 != 0) | |
73f7c32c | 53 | { |
ed19993b TR |
54 | futex_wait_simple (&cond->__data.__wrefs, wrefs, private); |
55 | /* See above. */ | |
56 | wrefs = atomic_load_acquire (&cond->__data.__wrefs); | |
73f7c32c | 57 | } |
ed19993b | 58 | /* The memory the condvar occupies can now be reused. */ |
76a50749 UD |
59 | return 0; |
60 | } | |
bf293afe UD |
61 | versioned_symbol (libpthread, __pthread_cond_destroy, |
62 | pthread_cond_destroy, GLIBC_2_3_2); |