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
|
/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <errno.h>
#include <pthread.h>
#include <stddef.h>
#include <unistd.h>
#include "async.h"
#include "errno-util.h"
#include "fd-util.h"
#include "log.h"
#include "macro.h"
#include "process-util.h"
#include "signal-util.h"
#include "util.h"
int asynchronous_job(void* (*func)(void *p), void *arg) {
sigset_t ss, saved_ss;
pthread_attr_t a;
pthread_t t;
int r, k;
/* It kinda sucks that we have to resort to threads to implement an asynchronous close(), but well, such is
* life. */
r = pthread_attr_init(&a);
if (r > 0)
return -r;
r = pthread_attr_setdetachstate(&a, PTHREAD_CREATE_DETACHED);
if (r > 0) {
r = -r;
goto finish;
}
assert_se(sigfillset(&ss) >= 0);
/* Block all signals before forking off the thread, so that the new thread is started with all signals
* blocked. This way the existence of the new thread won't affect signal handling in other threads. */
r = pthread_sigmask(SIG_BLOCK, &ss, &saved_ss);
if (r > 0) {
r = -r;
goto finish;
}
r = pthread_create(&t, &a, func, arg);
k = pthread_sigmask(SIG_SETMASK, &saved_ss, NULL);
if (r > 0)
r = -r;
else if (k > 0)
r = -k;
else
r = 0;
finish:
pthread_attr_destroy(&a);
return r;
}
int asynchronous_sync(pid_t *ret_pid) {
int r;
/* This forks off an invocation of fork() as a child process, in order to initiate synchronization to
* disk. Note that we implement this as helper process rather than thread as we don't want the sync() to hang our
* original process ever, and a thread would do that as the process can't exit with threads hanging in blocking
* syscalls. */
r = safe_fork("(sd-sync)", FORK_RESET_SIGNALS|FORK_CLOSE_ALL_FDS, ret_pid);
if (r < 0)
return r;
if (r == 0) {
/* Child process */
(void) sync();
_exit(EXIT_SUCCESS);
}
return 0;
}
static void *close_thread(void *p) {
(void) pthread_setname_np(pthread_self(), "close");
assert_se(close_nointr(PTR_TO_FD(p)) != -EBADF);
return NULL;
}
int asynchronous_close(int fd) {
int r;
/* This is supposed to behave similar to safe_close(), but
* actually invoke close() asynchronously, so that it will
* never block. Ideally the kernel would have an API for this,
* but it doesn't, so we work around it, and hide this as a
* far away as we can. */
if (fd >= 0) {
PROTECT_ERRNO;
r = asynchronous_job(close_thread, FD_TO_PTR(fd));
if (r < 0)
assert_se(close_nointr(fd) != -EBADF);
}
return -1;
}
|
