1/* Out-of-line notification function for the GSCOPE locking mechanism.
2 Copyright (C) 2007-2023 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
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
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19#include <nptl/descr.h>
20#include <futex-internal.h>
21#include <ldsodefs.h>
22#include <list.h>
23#include <lowlevellock.h>
24
25void
26__thread_gscope_wait (void)
27{
28 lll_lock (GL (dl_stack_cache_lock), LLL_PRIVATE);
29
30 struct pthread *self = THREAD_SELF;
31
32 /* Iterate over the list with system-allocated threads first. */
33 list_t *runp;
34 list_for_each (runp, &GL (dl_stack_used))
35 {
36 struct pthread *t = list_entry (runp, struct pthread, list);
37 if (t == self || t->header.gscope_flag == THREAD_GSCOPE_FLAG_UNUSED)
38 continue;
39
40 int *const gscope_flagp = &t->header.gscope_flag;
41
42 /* We have to wait until this thread is done with the global
43 scope. First tell the thread that we are waiting and
44 possibly have to be woken. */
45 if (atomic_compare_and_exchange_bool_acq (gscope_flagp,
46 THREAD_GSCOPE_FLAG_WAIT,
47 THREAD_GSCOPE_FLAG_USED))
48 continue;
49
50 do
51 futex_wait_simple ((unsigned int *) gscope_flagp,
52 THREAD_GSCOPE_FLAG_WAIT, FUTEX_PRIVATE);
53 while (*gscope_flagp == THREAD_GSCOPE_FLAG_WAIT);
54 }
55
56 /* Now the list with threads using user-allocated stacks. */
57 list_for_each (runp, &GL (dl_stack_user))
58 {
59 struct pthread *t = list_entry (runp, struct pthread, list);
60 if (t == self || t->header.gscope_flag == THREAD_GSCOPE_FLAG_UNUSED)
61 continue;
62
63 int *const gscope_flagp = &t->header.gscope_flag;
64
65 /* We have to wait until this thread is done with the global
66 scope. First tell the thread that we are waiting and
67 possibly have to be woken. */
68 if (atomic_compare_and_exchange_bool_acq (gscope_flagp,
69 THREAD_GSCOPE_FLAG_WAIT,
70 THREAD_GSCOPE_FLAG_USED))
71 continue;
72
73 do
74 futex_wait_simple ((unsigned int *) gscope_flagp,
75 THREAD_GSCOPE_FLAG_WAIT, FUTEX_PRIVATE);
76 while (*gscope_flagp == THREAD_GSCOPE_FLAG_WAIT);
77 }
78
79 lll_unlock (GL (dl_stack_cache_lock), LLL_PRIVATE);
80}
81