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d614a753 | 1 | /* Copyright (C) 2003-2020 Free Software Foundation, Inc. |
a88c9263 UD |
2 | This file is part of the GNU C Library. |
3 | Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>, 2003. | |
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/>. */ |
a88c9263 UD |
18 | |
19 | #include <endian.h> | |
20 | #include <errno.h> | |
21 | #include <sysdep.h> | |
ed19993b | 22 | #include <futex-internal.h> |
a88c9263 UD |
23 | #include <pthread.h> |
24 | #include <pthreadP.h> | |
5acf7263 | 25 | #include <stap-probe.h> |
ed19993b | 26 | #include <atomic.h> |
a88c9263 UD |
27 | |
28 | #include <shlib-compat.h> | |
29 | ||
ed19993b | 30 | #include "pthread_cond_common.c" |
a88c9263 | 31 | |
ed19993b TR |
32 | |
33 | /* We do the following steps from __pthread_cond_signal in one critical | |
34 | section: (1) signal all waiters in G1, (2) close G1 so that it can become | |
35 | the new G2 and make G2 the new G1, and (3) signal all waiters in the new | |
36 | G1. We don't need to do all these steps if there are no waiters in G1 | |
37 | and/or G2. See __pthread_cond_signal for further details. */ | |
a88c9263 | 38 | int |
9d46370c | 39 | __pthread_cond_broadcast (pthread_cond_t *cond) |
a88c9263 | 40 | { |
5acf7263 RM |
41 | LIBC_PROBE (cond_broadcast, 1, cond); |
42 | ||
ed19993b TR |
43 | unsigned int wrefs = atomic_load_relaxed (&cond->__data.__wrefs); |
44 | if (wrefs >> 3 == 0) | |
45 | return 0; | |
46 | int private = __condvar_get_private (wrefs); | |
47 | ||
48 | __condvar_acquire_lock (cond, private); | |
a88c9263 | 49 | |
ed19993b TR |
50 | unsigned long long int wseq = __condvar_load_wseq_relaxed (cond); |
51 | unsigned int g2 = wseq & 1; | |
52 | unsigned int g1 = g2 ^ 1; | |
53 | wseq >>= 1; | |
54 | bool do_futex_wake = false; | |
55 | ||
56 | /* Step (1): signal all waiters remaining in G1. */ | |
57 | if (cond->__data.__g_size[g1] != 0) | |
a88c9263 | 58 | { |
ed19993b TR |
59 | /* Add as many signals as the remaining size of the group. */ |
60 | atomic_fetch_add_relaxed (cond->__data.__g_signals + g1, | |
61 | cond->__data.__g_size[g1] << 1); | |
62 | cond->__data.__g_size[g1] = 0; | |
63 | ||
64 | /* We need to wake G1 waiters before we quiesce G1 below. */ | |
65 | /* TODO Only set it if there are indeed futex waiters. We could | |
66 | also try to move this out of the critical section in cases when | |
67 | G2 is empty (and we don't need to quiesce). */ | |
68 | futex_wake (cond->__data.__g_signals + g1, INT_MAX, private); | |
a88c9263 UD |
69 | } |
70 | ||
ed19993b TR |
71 | /* G1 is complete. Step (2) is next unless there are no waiters in G2, in |
72 | which case we can stop. */ | |
73 | if (__condvar_quiesce_and_switch_g1 (cond, wseq, &g1, private)) | |
74 | { | |
75 | /* Step (3): Send signals to all waiters in the old G2 / new G1. */ | |
76 | atomic_fetch_add_relaxed (cond->__data.__g_signals + g1, | |
77 | cond->__data.__g_size[g1] << 1); | |
78 | cond->__data.__g_size[g1] = 0; | |
79 | /* TODO Only set it if there are indeed futex waiters. */ | |
80 | do_futex_wake = true; | |
81 | } | |
82 | ||
83 | __condvar_release_lock (cond, private); | |
84 | ||
85 | if (do_futex_wake) | |
86 | futex_wake (cond->__data.__g_signals + g1, INT_MAX, private); | |
a88c9263 UD |
87 | |
88 | return 0; | |
89 | } | |
90 | ||
91 | versioned_symbol (libpthread, __pthread_cond_broadcast, pthread_cond_broadcast, | |
92 | GLIBC_2_3_2); |