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