1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
2
3 #include <errno.h>
4 #include <pthread.h>
5 #include <stddef.h>
6 #include <unistd.h>
7
8 #include "async.h"
9 #include "errno-util.h"
10 #include "fd-util.h"
11 #include "log.h"
12 #include "macro.h"
13 #include "process-util.h"
14 #include "signal-util.h"
15 #include "util.h"
16
asynchronous_job(void * (* func)(void * p),void * arg)17 int asynchronous_job(void* (*func)(void *p), void *arg) {
18 sigset_t ss, saved_ss;
19 pthread_attr_t a;
20 pthread_t t;
21 int r, k;
22
23 /* It kinda sucks that we have to resort to threads to implement an asynchronous close(), but well, such is
24 * life. */
25
26 r = pthread_attr_init(&a);
27 if (r > 0)
28 return -r;
29
30 r = pthread_attr_setdetachstate(&a, PTHREAD_CREATE_DETACHED);
31 if (r > 0) {
32 r = -r;
33 goto finish;
34 }
35
36 assert_se(sigfillset(&ss) >= 0);
37
38 /* Block all signals before forking off the thread, so that the new thread is started with all signals
39 * blocked. This way the existence of the new thread won't affect signal handling in other threads. */
40
41 r = pthread_sigmask(SIG_BLOCK, &ss, &saved_ss);
42 if (r > 0) {
43 r = -r;
44 goto finish;
45 }
46
47 r = pthread_create(&t, &a, func, arg);
48
49 k = pthread_sigmask(SIG_SETMASK, &saved_ss, NULL);
50
51 if (r > 0)
52 r = -r;
53 else if (k > 0)
54 r = -k;
55 else
56 r = 0;
57
58 finish:
59 pthread_attr_destroy(&a);
60 return r;
61 }
62
asynchronous_sync(pid_t * ret_pid)63 int asynchronous_sync(pid_t *ret_pid) {
64 int r;
65
66 /* This forks off an invocation of fork() as a child process, in order to initiate synchronization to
67 * disk. Note that we implement this as helper process rather than thread as we don't want the sync() to hang our
68 * original process ever, and a thread would do that as the process can't exit with threads hanging in blocking
69 * syscalls. */
70
71 r = safe_fork("(sd-sync)", FORK_RESET_SIGNALS|FORK_CLOSE_ALL_FDS, ret_pid);
72 if (r < 0)
73 return r;
74 if (r == 0) {
75 /* Child process */
76 (void) sync();
77 _exit(EXIT_SUCCESS);
78 }
79
80 return 0;
81 }
82
close_thread(void * p)83 static void *close_thread(void *p) {
84 (void) pthread_setname_np(pthread_self(), "close");
85
86 assert_se(close_nointr(PTR_TO_FD(p)) != -EBADF);
87 return NULL;
88 }
89
asynchronous_close(int fd)90 int asynchronous_close(int fd) {
91 int r;
92
93 /* This is supposed to behave similar to safe_close(), but
94 * actually invoke close() asynchronously, so that it will
95 * never block. Ideally the kernel would have an API for this,
96 * but it doesn't, so we work around it, and hide this as a
97 * far away as we can. */
98
99 if (fd >= 0) {
100 PROTECT_ERRNO;
101
102 r = asynchronous_job(close_thread, FD_TO_PTR(fd));
103 if (r < 0)
104 assert_se(close_nointr(fd) != -EBADF);
105 }
106
107 return -1;
108 }
109