shared: move async.[ch] from src/basic/ → src/shared/
That way we can later add an async wrapper for rm_rf() which is in src/shared/, too.
This commit is contained in:
Lennart Poettering
@@ -1,160 +0,0 @@
|
||||
/* SPDX-License-Identifier: LGPL-2.1-or-later */
|
||||
|
||||
#include <errno.h>
|
||||
#include <pthread.h>
|
||||
#include <stddef.h>
|
||||
#include <sys/prctl.h>
|
||||
#include <sys/wait.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"
|
||||
|
||||
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 */
|
||||
sync();
|
||||
_exit(EXIT_SUCCESS);
|
||||
}
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
/* We encode the fd to close in the userdata pointer as an unsigned value. The highest bit indicates whether
|
||||
* we need to fork again */
|
||||
#define NEED_DOUBLE_FORK (1U << (sizeof(unsigned) * 8 - 1))
|
||||
|
||||
static int close_func(void *p) {
|
||||
unsigned v = PTR_TO_UINT(p);
|
||||
|
||||
(void) prctl(PR_SET_NAME, (unsigned long*) "(close)");
|
||||
|
||||
/* Note: 💣 This function is invoked in a child process created via glibc's clone() wrapper. In such
|
||||
* children memory allocation is not allowed, since glibc does not release malloc mutexes in
|
||||
* clone() 💣 */
|
||||
|
||||
if (v & NEED_DOUBLE_FORK) {
|
||||
pid_t pid;
|
||||
|
||||
v &= ~NEED_DOUBLE_FORK;
|
||||
|
||||
/* This inner child will be reparented to the subreaper/PID 1. Here we turn on SIGCHLD, so
|
||||
* that the reaper knows when it's time to reap. */
|
||||
pid = clone_with_nested_stack(close_func, SIGCHLD|CLONE_FILES, UINT_TO_PTR(v));
|
||||
if (pid >= 0)
|
||||
return 0;
|
||||
}
|
||||
|
||||
close((int) v); /* no assert() here, we are in the child and the result would be eaten up anyway */
|
||||
return 0;
|
||||
}
|
||||
|
||||
int asynchronous_close(int fd) {
|
||||
unsigned v;
|
||||
pid_t pid;
|
||||
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.
|
||||
*
|
||||
* It is important to us that we don't use threads (via glibc pthread) in PID 1, hence we'll do a
|
||||
* minimal subprocess instead which shares our fd table via CLONE_FILES. */
|
||||
|
||||
if (fd < 0)
|
||||
return -EBADF; /* already invalid */
|
||||
|
||||
PROTECT_ERRNO;
|
||||
|
||||
v = (unsigned) fd;
|
||||
|
||||
/* We want to fork off a process that is automatically reaped. For that we'd usually double-fork. But
|
||||
* we can optimize this a bit: if we are PID 1 or a subreaper anyway (the systemd service manager
|
||||
* process qualifies as this), we can avoid the double forking, since the double forked process would
|
||||
* be reparented back to us anyway. */
|
||||
r = is_reaper_process();
|
||||
if (r < 0)
|
||||
log_debug_errno(r, "Cannot determine if we are a reaper process, assuming we are not: %m");
|
||||
if (r <= 0)
|
||||
v |= NEED_DOUBLE_FORK;
|
||||
|
||||
pid = clone_with_nested_stack(close_func, CLONE_FILES | ((v & NEED_DOUBLE_FORK) ? 0 : SIGCHLD), UINT_TO_PTR(v));
|
||||
if (pid < 0)
|
||||
assert_se(close_nointr(fd) != -EBADF); /* local fallback */
|
||||
else if (v & NEED_DOUBLE_FORK) {
|
||||
|
||||
/* Reap the intermediate child. Key here is that we specify __WCLONE, since we didn't ask for
|
||||
* any signal to be sent to us on process exit, and otherwise waitid() would refuse waiting
|
||||
* then.
|
||||
*
|
||||
* We usually prefer calling waitid(), but before kernel 4.7 it didn't support __WCLONE while
|
||||
* waitpid() did. Hence let's use waitpid() here, it's good enough for our purposes here. */
|
||||
for (;;) {
|
||||
if (waitpid(pid, NULL, WEXITED|__WCLONE) >= 0 || errno != EINTR)
|
||||
break;
|
||||
}
|
||||
}
|
||||
|
||||
return -EBADF; /* return an invalidated fd */
|
||||
}
|
||||
@@ -1,13 +0,0 @@
|
||||
/* SPDX-License-Identifier: LGPL-2.1-or-later */
|
||||
#pragma once
|
||||
|
||||
#include <sys/types.h>
|
||||
|
||||
#include "macro.h"
|
||||
|
||||
int asynchronous_job(void* (*func)(void *p), void *arg);
|
||||
|
||||
int asynchronous_sync(pid_t *ret_pid);
|
||||
int asynchronous_close(int fd);
|
||||
|
||||
DEFINE_TRIVIAL_CLEANUP_FUNC(int, asynchronous_close);
|
||||
@@ -7,7 +7,6 @@ basic_sources = files(
|
||||
'architecture.c',
|
||||
'argv-util.c',
|
||||
'arphrd-util.c',
|
||||
'async.c',
|
||||
'audit-util.c',
|
||||
'build.c',
|
||||
'bus-label.c',
|
||||
|
||||
Reference in New Issue
Block a user