1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
|
/* Copyright (C) 2002-2021 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <fork.h>
#include <atomic.h>
#define DYNARRAY_ELEMENT struct fork_handler
#define DYNARRAY_STRUCT fork_handler_list
#define DYNARRAY_PREFIX fork_handler_list_
#define DYNARRAY_INITIAL_SIZE 48
#include <malloc/dynarray-skeleton.c>
static struct fork_handler_list fork_handlers;
static bool fork_handler_init = false;
static int atfork_lock = LLL_LOCK_INITIALIZER;
int
__register_atfork (void (*prepare) (void), void (*parent) (void),
void (*child) (void), void *dso_handle)
{
lll_lock (atfork_lock, LLL_PRIVATE);
if (!fork_handler_init)
{
fork_handler_list_init (&fork_handlers);
fork_handler_init = true;
}
struct fork_handler *newp = fork_handler_list_emplace (&fork_handlers);
if (newp != NULL)
{
newp->prepare_handler = prepare;
newp->parent_handler = parent;
newp->child_handler = child;
newp->dso_handle = dso_handle;
}
/* Release the lock. */
lll_unlock (atfork_lock, LLL_PRIVATE);
return newp == NULL ? ENOMEM : 0;
}
libc_hidden_def (__register_atfork)
static struct fork_handler *
fork_handler_list_find (struct fork_handler_list *fork_handlers,
void *dso_handle)
{
for (size_t i = 0; i < fork_handler_list_size (fork_handlers); i++)
{
struct fork_handler *elem = fork_handler_list_at (fork_handlers, i);
if (elem->dso_handle == dso_handle)
return elem;
}
return NULL;
}
void
__unregister_atfork (void *dso_handle)
{
lll_lock (atfork_lock, LLL_PRIVATE);
struct fork_handler *first = fork_handler_list_find (&fork_handlers,
dso_handle);
/* Removing is done by shifting the elements in the way the elements
that are not to be removed appear in the beginning in dynarray.
This avoid the quadradic run-time if a naive strategy to remove and
shift one element at time. */
if (first != NULL)
{
struct fork_handler *new_end = first;
first++;
for (; first != fork_handler_list_end (&fork_handlers); ++first)
{
if (first->dso_handle != dso_handle)
{
*new_end = *first;
++new_end;
}
}
ptrdiff_t removed = first - new_end;
for (size_t i = 0; i < removed; i++)
fork_handler_list_remove_last (&fork_handlers);
}
lll_unlock (atfork_lock, LLL_PRIVATE);
}
void
__run_fork_handlers (enum __run_fork_handler_type who, _Bool do_locking)
{
struct fork_handler *runp;
if (who == atfork_run_prepare)
{
if (do_locking)
lll_lock (atfork_lock, LLL_PRIVATE);
size_t sl = fork_handler_list_size (&fork_handlers);
for (size_t i = sl; i > 0; i--)
{
runp = fork_handler_list_at (&fork_handlers, i - 1);
if (runp->prepare_handler != NULL)
runp->prepare_handler ();
}
}
else
{
size_t sl = fork_handler_list_size (&fork_handlers);
for (size_t i = 0; i < sl; i++)
{
runp = fork_handler_list_at (&fork_handlers, i);
if (who == atfork_run_child && runp->child_handler)
runp->child_handler ();
else if (who == atfork_run_parent && runp->parent_handler)
runp->parent_handler ();
}
if (do_locking)
lll_unlock (atfork_lock, LLL_PRIVATE);
}
}
libc_freeres_fn (free_mem)
{
lll_lock (atfork_lock, LLL_PRIVATE);
fork_handler_list_free (&fork_handlers);
lll_unlock (atfork_lock, LLL_PRIVATE);
}
|
