libudev: queue provide file descriptor to watch busy event queue

docs/libudev/libudev-sections.txt

@@ -116,6 +116,8 @@ udev_queue_get_seqnum_sequence_is_finished
 udev_queue_get_queued_list_entry
 udev_queue_get_kernel_seqnum
 udev_queue_get_udev_seqnum
+udev_queue_get_fd
+udev_queue_flush
 </SECTION>
 
 <SECTION>

src/libudev/libudev-queue.c

@@ -26,6 +26,7 @@
 #include <string.h>
 #include <limits.h>
 #include <sys/stat.h>
+#include <sys/inotify.h>
 
 #include "libudev.h"
 #include "libudev-private.h"
@@ -45,6 +46,7 @@
 struct udev_queue {
         struct udev *udev;
         int refcount;
+        int fd;
 };
 
 /**
@@ -69,6 +71,7 @@ _public_ struct udev_queue *udev_queue_new(struct udev *udev)
 
         udev_queue->refcount = 1;
         udev_queue->udev = udev;
+        udev_queue->fd = -1;
         return udev_queue;
 }
 
@@ -107,6 +110,8 @@ _public_ struct udev_queue *udev_queue_unref(struct udev_queue *udev_queue)
         if (udev_queue->refcount > 0)
                 return NULL;
 
+        safe_close(udev_queue->fd);
+
         free(udev_queue);
         return NULL;
 }
@@ -222,3 +227,44 @@ _public_ struct udev_list_entry *udev_queue_get_queued_list_entry(struct udev_qu
 {
         return NULL;
 }
+
+/**
+ * udev_queue_get_fd:
+ * @udev_queue: udev queue context
+ *
+ * Returns: a file descriptor to watch for a queue to become empty.
+ */
+_public_ int udev_queue_get_fd(struct udev_queue *udev_queue) {
+        int fd;
+        int r;
+
+        if (udev_queue->fd >= 0)
+                return udev_queue->fd;
+
+        fd = inotify_init1(IN_CLOEXEC);
+        if (fd < 0)
+                return -errno;
+
+        r = inotify_add_watch(fd, "/run/udev/queue" , IN_DELETE);
+        if (r < 0) {
+                r = -errno;
+                close(fd);
+                return r;
+        }
+
+        udev_queue->fd = fd;
+        return fd;
+}
+
+/**
+ * udev_queue_flush:
+ * @udev_queue: udev queue context
+ *
+ * Returns: the result of clearing the watch for queue changes.
+ */
+_public_ int udev_queue_flush(struct udev_queue *udev_queue) {
+        if (udev_queue->fd < 0)
+                return -EINVAL;
+
+        return flush_fd(udev_queue->fd);
+}

src/libudev/libudev.h

@@ -177,6 +177,8 @@ int udev_queue_get_queue_is_empty(struct udev_queue *udev_queue);
 int udev_queue_get_seqnum_is_finished(struct udev_queue *udev_queue, unsigned long long int seqnum) __attribute__ ((deprecated));
 int udev_queue_get_seqnum_sequence_is_finished(struct udev_queue *udev_queue,
                                                unsigned long long int start, unsigned long long int end) __attribute__ ((deprecated));
+int udev_queue_get_fd(struct udev_queue *udev_queue);
+int udev_queue_flush(struct udev_queue *udev_queue);
 struct udev_list_entry *udev_queue_get_queued_list_entry(struct udev_queue *udev_queue) __attribute__ ((deprecated));
 
 /*

src/libudev/libudev.sym

@@ -82,6 +82,8 @@ global:
         udev_queue_get_udev;
         udev_queue_get_udev_is_active;
         udev_queue_get_udev_seqnum;
+        udev_queue_get_fd;
+        udev_queue_flush;
         udev_queue_new;
         udev_queue_ref;
         udev_queue_unref;

src/udev/udevadm-settle.c

@@ -29,7 +29,6 @@
 #include <getopt.h>
 #include <signal.h>
 #include <time.h>
-#include <sys/inotify.h>
 #include <sys/poll.h>
 #include <sys/stat.h>
 #include <sys/types.h>
@@ -59,7 +58,9 @@ static int adm_settle(struct udev *udev, int argc, char *argv[])
         const char *exists = NULL;
         unsigned int timeout = 120;
         struct pollfd pfd[1] = { {.fd = -1}, };
-        int rc = EXIT_FAILURE, c;
+        int c;
+        struct udev_queue *queue;
+        int rc = EXIT_FAILURE;
 
         while ((c = getopt_long(argc, argv, "s:e:t:E:qh", options, NULL)) >= 0) {
                 switch (c) {
@@ -79,9 +80,9 @@ static int adm_settle(struct udev *udev, int argc, char *argv[])
                         break;
                 case 'h':
                         help();
-                        exit(EXIT_SUCCESS);
+                        return EXIT_SUCCESS;
                 case '?':
-                        exit(EXIT_FAILURE);
+                        return EXIT_FAILURE;
                 default:
                         assert_not_reached("Unknown argument");
                 }
@@ -89,7 +90,7 @@ static int adm_settle(struct udev *udev, int argc, char *argv[])
 
         if (optind < argc) {
                 fprintf(stderr, "Extraneous argument: '%s'\n", argv[optind]);
-                exit(EXIT_FAILURE);
+                return EXIT_FAILURE;
         }
 
         /* guarantee that the udev daemon isn't pre-processing */
@@ -101,26 +102,23 @@ static int adm_settle(struct udev *udev, int argc, char *argv[])
                         if (udev_ctrl_send_ping(uctrl, timeout) < 0) {
                                 log_debug("no connection to daemon");
                                 udev_ctrl_unref(uctrl);
-                                rc = EXIT_SUCCESS;
+                                return EXIT_SUCCESS;
-                                goto out;
                         }
                         udev_ctrl_unref(uctrl);
                 }
         }
 
-        pfd[0].events = POLLIN;
+        queue = udev_queue_new(udev);
-        pfd[0].fd = inotify_init1(IN_CLOEXEC);
+        if (!queue) {
-        if (pfd[0].fd < 0) {
+                log_error("unable to get udev queue");
-                log_error("inotify_init failed: %m");
+                return EXIT_FAILURE;
-                goto out;
         }
 
-        if (inotify_add_watch(pfd[0].fd, "/run/udev/queue" , IN_DELETE) < 0) {
+        pfd[0].events = POLLIN;
-                /* If it does not exist, we don't have to wait */
+        pfd[0].fd = udev_queue_get_fd(queue);
-                if (errno == ENOENT)
+        if (pfd[0].fd < 0) {
-                        rc = EXIT_SUCCESS;
+                log_debug("queue is empty, nothing to watch");
-                else
+                rc = EXIT_SUCCESS;
-                        log_debug("watching /run/udev/queue failed");
                 goto out;
         }
 
@@ -131,22 +129,18 @@ static int adm_settle(struct udev *udev, int argc, char *argv[])
                 }
 
                 /* exit if queue is empty */
-                if (access("/run/udev/queue", F_OK) < 0) {
+                if (udev_queue_get_queue_is_empty(queue)) {
                         rc = EXIT_SUCCESS;
                         break;
                 }
 
-                /* wake up when "queue" file is deleted */
+                /* wake up when queue is empty */
-                if (poll(pfd, 1, 100) > 0 && pfd[0].revents & POLLIN) {
+                if (poll(pfd, 1, 100) > 0 && pfd[0].revents & POLLIN)
-                        char buf[sizeof(struct inotify_event) + PATH_MAX];
+                        udev_queue_flush(queue);
-
-                        read(pfd[0].fd, buf, sizeof(buf));
-                }
         }
 
 out:
-        if (pfd[0].fd >= 0)
+        udev_queue_unref(queue);
-                close(pfd[0].fd);
         return rc;
 }