build-sys: split internal basic/ library from shared/

basic/      can be used by everything
            cannot use anything outside of basic/

libsystemd/ can use basic/
            cannot use shared/

shared/     can use libsystemd/

src/basic/async.c

@@ -0,0 +1,92 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2013 Lennart Poettering
+
+  systemd 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.
+
+  systemd 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 systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <pthread.h>
+#include <unistd.h>
+
+#include "async.h"
+#include "log.h"
+#include "util.h"
+
+int asynchronous_job(void* (*func)(void *p), void *arg) {
+        pthread_attr_t a;
+        pthread_t t;
+        int r;
+
+        /* It kinda sucks that we have to resort to threads to
+         * implement an asynchronous sync(), but well, such is
+         * life.
+         *
+         * Note that issuing this command right before exiting a
+         * process will cause the process to wait for the sync() to
+         * complete. This function hence is nicely asynchronous really
+         * only in long running processes. */
+
+        r = pthread_attr_init(&a);
+        if (r > 0)
+                return -r;
+
+        r = pthread_attr_setdetachstate(&a, PTHREAD_CREATE_DETACHED);
+        if (r > 0)
+                goto finish;
+
+        r = pthread_create(&t, &a, func, arg);
+
+finish:
+        pthread_attr_destroy(&a);
+        return -r;
+}
+
+static void *sync_thread(void *p) {
+        sync();
+        return NULL;
+}
+
+int asynchronous_sync(void) {
+        log_debug("Spawning new thread for sync");
+
+        return asynchronous_job(sync_thread, NULL);
+}
+
+static void *close_thread(void *p) {
+        assert_se(close_nointr(PTR_TO_INT(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, INT_TO_PTR(fd));
+                if (r < 0)
+                         assert_se(close_nointr(fd) != -EBADF);
+        }
+
+        return -1;
+}