libudev: record and export "age" of device record

configure.ac

@@ -12,6 +12,8 @@ GTK_DOC_CHECK(1.10)
 AC_PREFIX_DEFAULT([/usr])
 AC_PATH_PROG([XSLTPROC], [xsltproc])
 
+AC_SEARCH_LIBS([clock_gettime], [rt], [], [AC_MSG_ERROR([POSIX RT library not found])])
+
 AC_ARG_WITH([rootlibdir],
 	AS_HELP_STRING([--with-rootlibdir=DIR], [rootfs directory to install shared libraries]),
 	[], [with_rootlibdir=$libdir])

libudev/docs/libudev-sections.txt

@@ -55,6 +55,7 @@ udev_device_get_devnum
 udev_device_get_action
 udev_device_get_sysattr_value
 udev_device_get_seqnum
+udev_device_get_usec_since_initialized
 </SECTION>
 
 <SECTION>

libudev/exported_symbols

@@ -37,6 +37,7 @@ udev_device_get_action
 udev_device_get_driver
 udev_device_get_devnum
 udev_device_get_seqnum
+udev_device_get_usec_since_initialized
 udev_device_get_sysattr_value
 udev_enumerate_new
 udev_enumerate_ref

libudev/libudev-device-private.c

@@ -147,6 +147,8 @@ int udev_device_update_db(struct udev_device *udev_device)
 			fprintf(f, "L:%i\n", udev_device_get_devlink_priority(udev_device));
 		if (udev_device_get_watch_handle(udev_device) >= 0)
 			fprintf(f, "W:%i\n", udev_device_get_watch_handle(udev_device));
+		if (udev_device_get_usec_initialized(udev_device) > 0)
+			fprintf(f, "I:%llu\n", udev_device_get_usec_initialized(udev_device));
 		udev_list_entry_foreach(list_entry, udev_device_get_properties_list_entry(udev_device)) {
 			if (!udev_list_entry_get_flags(list_entry))
 				continue;

libudev/libudev-device.c

@@ -63,6 +63,7 @@ struct udev_device {
 	struct udev_list_node sysattr_list;
 	struct udev_list_node tags_list;
 	unsigned long long int seqnum;
+	unsigned long long int usec_initialized;
 	int event_timeout;
 	int timeout;
 	int devlink_priority;
@@ -284,6 +285,9 @@ int udev_device_read_db(struct udev_device *udev_device)
 		case 'W':
 			udev_device_set_watch_handle(udev_device, atoi(val));
 			break;
+		case 'I':
+			udev_device_set_usec_initialized(udev_device, strtoull(val, NULL, 10));
+			break;
 		}
 	}
 	fclose(f);
@@ -1094,6 +1098,44 @@ unsigned long long int udev_device_get_seqnum(struct udev_device *udev_device)
 	return udev_device->seqnum;
 }
 
+/**
+ * udev_device_get_usec_since_initialized:
+ * @udev_device: udev device
+ *
+ * Return the number of microseconds passed since udev set up the
+ * device for the first time.
+ *
+ * This is only implemented for devices with need to store properties
+ * in the udev database. All other devices return 0 here.
+ *
+ * Returns: the number of microseconds since the device was first seen.
+ **/
+unsigned long long int udev_device_get_usec_since_initialized(struct udev_device *udev_device)
+{
+	unsigned long long now;
+
+	if (udev_device == NULL)
+		return 0;
+	if (!udev_device->info_loaded)
+		udev_device_read_db(udev_device);
+	if (udev_device->usec_initialized == 0)
+		return 0;
+	now = usec_monotonic();
+	if (now == 0)
+		return 0;
+	return now - udev_device->usec_initialized;
+}
+
+unsigned long long udev_device_get_usec_initialized(struct udev_device *udev_device)
+{
+	return udev_device->usec_initialized;
+}
+
+void udev_device_set_usec_initialized(struct udev_device *udev_device, unsigned long long usec_initialized)
+{
+	udev_device->usec_initialized = usec_initialized;
+}
+
 /**
  * udev_device_get_sysattr_value:
  * @udev_device: udev device
@@ -1318,7 +1360,7 @@ const char *udev_device_get_id_filename(struct udev_device *udev_device)
  * device node permissions and context, or has renamed a network
  * device.
  *
- * For now, this is only implemented for devices with a device node
+ * This is only implemented for devices with a device node
  * or network interfaces. All other devices return 1 here.
  *
  * Returns: 1 if the device is set up. 0 otherwise.

libudev/libudev-private.h

@@ -98,6 +98,8 @@ int udev_device_get_event_timeout(struct udev_device *udev_device);
 int udev_device_set_event_timeout(struct udev_device *udev_device, int event_timeout);
 int udev_device_set_devnum(struct udev_device *udev_device, dev_t devnum);
 int udev_device_set_seqnum(struct udev_device *udev_device, unsigned long long int seqnum);
+unsigned long long udev_device_get_usec_initialized(struct udev_device *udev_device);
+void udev_device_set_usec_initialized(struct udev_device *udev_device, unsigned long long usec_initialized);
 int udev_device_get_devlink_priority(struct udev_device *udev_device);
 int udev_device_set_devlink_priority(struct udev_device *udev_device, int prio);
 int udev_device_get_watch_handle(struct udev_device *udev_device);
@@ -224,6 +226,7 @@ int util_run_program(struct udev *udev, const char *command, char **envp,
 		     const sigset_t *sigmask, bool reset_prio);
 int util_resolve_subsys_kernel(struct udev *udev, const char *string,
 				      char *result, size_t maxsize, int read_value);
+unsigned long long usec_monotonic(void);
 
 /* libudev-selinux-private.c */
 #ifndef WITH_SELINUX

libudev/libudev-util.c

@@ -18,6 +18,7 @@
 #include <dirent.h>
 #include <ctype.h>
 #include <fcntl.h>
+#include <time.h>
 #include <sys/stat.h>
 
 #include "libudev.h"
@@ -553,3 +554,15 @@ uint64_t util_string_bloom64(const char *str)
 	bits |= 1LLU << ((hash >> 18) & 63);
 	return bits;
 }
+
+#define USEC_PER_SEC  1000000ULL
+#define NSEC_PER_USEC 1000ULL
+unsigned long long usec_monotonic(void)
+{
+	struct timespec ts;
+
+	if (clock_gettime(CLOCK_MONOTONIC, &ts) != 0)
+		return 0;
+	return (unsigned long long) ts.tv_sec * USEC_PER_SEC +
+	       (unsigned long long) ts.tv_nsec / NSEC_PER_USEC;
+}

libudev/libudev.h

@@ -97,6 +97,7 @@ const char *udev_device_get_driver(struct udev_device *udev_device);
 dev_t udev_device_get_devnum(struct udev_device *udev_device);
 const char *udev_device_get_action(struct udev_device *udev_device);
 unsigned long long int udev_device_get_seqnum(struct udev_device *udev_device);
+unsigned long long int udev_device_get_usec_since_initialized(struct udev_device *udev_device);
 const char *udev_device_get_sysattr_value(struct udev_device *udev_device, const char *sysattr);
 
 /*

libudev/libudev.pc.in

@@ -6,6 +6,6 @@ includedir=@prefix@/include
 Name: libudev
 Description: Library to access udev device information
 Version: @VERSION@
-Libs: -L${libdir} -ludev
+Libs: -L${libdir} -ludev -lrt
 Libs.private: 
 Cflags: -I${includedir}

udev/udev-event.c

@@ -643,6 +643,13 @@ int udev_event_execute_rules(struct udev_event *event, struct udev_rules *rules)
 			err = udev_node_add(dev, event->mode, event->uid, event->gid);
 		}
 
+		/* preserve old, or get new initialization timestamp */
+		if (event->dev_db != NULL && udev_device_get_usec_initialized(event->dev_db) > 0)
+			udev_device_set_usec_initialized(event->dev, udev_device_get_usec_initialized(event->dev_db));
+		else
+			udev_device_set_usec_initialized(event->dev, usec_monotonic());
+
+		/* (re)write database file */
 		udev_device_update_db(dev);
 		udev_device_tag_index(dev, event->dev_db, true);
 		udev_device_set_is_initialized(dev);