[systemd-devel] [PATCH v2 01/10] logind: listen actively for session devices

Discussion:

David Herrmann

2013-09-17 15:39:54 UTC

Session compositors need access to fbdev, DRM and evdev devices if they
control a session. To make logind pass them to sessions, we need to
listen for them actively.

However, we avoid creating new seats for non master-of-seat devices. Only
once a seat is created, we start remembering all other session devices. If
the last master-device is removed (even if there are other non-master
devices still available), we destroy the seat. This is the current
behavior, but we need to explicitly implement it now as there may be
non-master devices in the seat->devices list.

Unlike master devices, we don't care whether our list of non-master
devices is complete. We don't export this list but use it only as cache if
sessions request these devices. Hence, if a session requests a device that
is not in the list, we will simply look it up. However, once a session
requested a device, we must be notified of "remove" udev events. So we
must link the devices somehow into the device-list.

Regarding the implementation, we now sort the device list by the "master"
flag. This guarantees that master devices are at the front and non-master
devices at the tail of the list. Thus, we can easily test whether a seat
has a master device attached.
---
src/login/logind-device.c | 35 ++++++++++++++++++---
src/login/logind-device.h | 3 +-
src/login/logind-seat.c | 11 +++++--
src/login/logind-seat.h | 1 +
src/login/logind.c | 79 +++++++++++++++++++++++++++++++++++++++++------
src/login/logind.h | 6 ++--
6 files changed, 116 insertions(+), 19 deletions(-)

diff --git a/src/login/logind-device.c b/src/login/logind-device.c
index 51b1535..a9a9633 100644
--- a/src/login/logind-device.c
+++ b/src/login/logind-device.c
@@ -25,7 +25,7 @@
#include "logind-device.h"
#include "util.h"

-Device* device_new(Manager *m, const char *sysfs) {
+Device* device_new(Manager *m, const char *sysfs, bool master) {
Device *d;

assert(m);
@@ -48,6 +48,7 @@ Device* device_new(Manager *m, const char *sysfs) {
}

d->manager = m;
+ d->master = master;
dual_timestamp_get(&d->timestamp);

return d;
@@ -75,11 +76,16 @@ void device_detach(Device *d) {
LIST_REMOVE(Device, devices, d->seat->devices, d);
d->seat = NULL;

- seat_add_to_gc_queue(s);
- seat_send_changed(s, "CanGraphical\0");
+ if (!seat_has_master_device(s)) {
+ seat_add_to_gc_queue(s);
+ seat_send_changed(s, "CanGraphical\0");
+ }
}

void device_attach(Device *d, Seat *s) {
+ Device *i;
+ bool had_master;
+
assert(d);
assert(s);

@@ -90,7 +96,26 @@ void device_attach(Device *d, Seat *s) {
device_detach(d);

d->seat = s;
- LIST_PREPEND(Device, devices, s->devices, d);
+ had_master = seat_has_master_device(s);
+
+ /* We keep the device list sorted by the "master" flag. That is, master
+ * devices are at the front, other devices at the tail. As there is no
+ * way to easily add devices at the list-tail, we need to iterate the
+ * list to find the first non-master device when adding non-master
+ * devices. We assume there is only a few (normally 1) master devices
+ * per seat, so we iterate only a few times. */
+
+ if (d->master || !s->devices) {
+ LIST_PREPEND(Device, devices, s->devices, d);
+ } else {
+ LIST_FOREACH(devices, i, s->devices) {
+ if (!i->devices_next || !i->master) {
+ LIST_INSERT_AFTER(Device, devices, s->devices, i, d);
+ break;
+ }
+ }
+ }

- seat_send_changed(s, "CanGraphical\0");
+ if (!had_master && d->master)
+ seat_send_changed(s, "CanGraphical\0");
}
diff --git a/src/login/logind-device.h b/src/login/logind-device.h
index 3b15356..315f0e6 100644
--- a/src/login/logind-device.h
+++ b/src/login/logind-device.h
@@ -33,13 +33,14 @@ struct Device {

char *sysfs;
Seat *seat;
+ bool master;

dual_timestamp timestamp;

LIST_FIELDS(struct Device, devices);
};

-Device* device_new(Manager *m, const char *sysfs);
+Device* device_new(Manager *m, const char *sysfs, bool master);
void device_free(Device *d);
void device_attach(Device *d, Seat *s);
void device_detach(Device *d);
diff --git a/src/login/logind-seat.c b/src/login/logind-seat.c
index 470d08b..2c60b8a 100644
--- a/src/login/logind-seat.c
+++ b/src/login/logind-seat.c
@@ -448,10 +448,17 @@ bool seat_can_tty(Seat *s) {
return seat_is_vtconsole(s);
}

+bool seat_has_master_device(Seat *s) {
+ assert(s);
+
+ /* device list is ordered by "master" flag */
+ return !!s->devices && s->devices->master;
+}
+
bool seat_can_graphical(Seat *s) {
assert(s);

- return !!s->devices;
+ return seat_has_master_device(s);
}

int seat_get_idle_hint(Seat *s, dual_timestamp *t) {
@@ -499,7 +506,7 @@ int seat_check_gc(Seat *s, bool drop_not_started) {
if (seat_is_vtconsole(s))
return 1;

- return !!s->devices;
+ return seat_has_master_device(s);
}

void seat_add_to_gc_queue(Seat *s) {
diff --git a/src/login/logind-seat.h b/src/login/logind-seat.h
index c8ab17f..bd5390f 100644
--- a/src/login/logind-seat.h
+++ b/src/login/logind-seat.h
@@ -63,6 +63,7 @@ int seat_attach_session(Seat *s, Session *session);
bool seat_is_vtconsole(Seat *s);
bool seat_can_multi_session(Seat *s);
bool seat_can_tty(Seat *s);
+bool seat_has_master_device(Seat *s);
bool seat_can_graphical(Seat *s);

int seat_get_idle_hint(Seat *s, dual_timestamp *t);
diff --git a/src/login/logind.c b/src/login/logind.c
index 4ef92b8..29019c2 100644
--- a/src/login/logind.c
+++ b/src/login/logind.c
@@ -151,6 +151,8 @@ void manager_free(Manager *m) {

if (m->udev_seat_monitor)
udev_monitor_unref(m->udev_seat_monitor);
+ if (m->udev_device_monitor)
+ udev_monitor_unref(m->udev_device_monitor);
if (m->udev_vcsa_monitor)
udev_monitor_unref(m->udev_vcsa_monitor);
if (m->udev_button_monitor)
@@ -184,7 +186,7 @@ void manager_free(Manager *m) {
free(m);
}

-int manager_add_device(Manager *m, const char *sysfs, Device **_device) {
+int manager_add_device(Manager *m, const char *sysfs, bool master, Device **_device) {
Device *d;

assert(m);
@@ -195,10 +197,13 @@ int manager_add_device(Manager *m, const char *sysfs, Device **_device) {
if (_device)
*_device = d;

+ /* we support adding master-flags, but not removing them */
+ d->master = d->master || master;
+
return 0;
}

- d = device_new(m, sysfs);
+ d = device_new(m, sysfs, master);
if (!d)
return -ENOMEM;

@@ -373,7 +378,8 @@ int manager_process_seat_device(Manager *m, struct udev_device *d) {

} else {
const char *sn;
- Seat *seat;
+ Seat *seat = NULL;
+ bool master;

sn = udev_device_get_property_value(d, "ID_SEAT");
if (isempty(sn))
@@ -384,16 +390,23 @@ int manager_process_seat_device(Manager *m, struct udev_device *d) {
return 0;
}

- r = manager_add_device(m, udev_device_get_syspath(d), &device);
+ /* ignore non-master devices for unknown seats */
+ master = udev_device_has_tag(d, "master-of-seat");
+ if (!master && !(seat = hashmap_get(m->seats, sn)))
+ return 0;
+
+ r = manager_add_device(m, udev_device_get_syspath(d), master, &device);
if (r < 0)
return r;

- r = manager_add_seat(m, sn, &seat);
- if (r < 0) {
- if (!device->seat)
- device_free(device);
+ if (!seat) {
+ r = manager_add_seat(m, sn, &seat);
+ if (r < 0) {
+ if (!device->seat)
+ device_free(device);

- return r;
+ return r;
+ }
}

device_attach(device, seat);
@@ -762,6 +775,22 @@ int manager_dispatch_seat_udev(Manager *m) {
return r;
}

+static int manager_dispatch_device_udev(Manager *m) {
+ struct udev_device *d;
+ int r;
+
+ assert(m);
+
+ d = udev_monitor_receive_device(m->udev_device_monitor);
+ if (!d)
+ return -ENOMEM;
+
+ r = manager_process_seat_device(m, d);
+ udev_device_unref(d);
+
+ return r;
+}
+
int manager_dispatch_vcsa_udev(Manager *m) {
struct udev_device *d;
int r = 0;
@@ -1149,6 +1178,7 @@ static int manager_connect_udev(Manager *m) {

assert(m);
assert(!m->udev_seat_monitor);
+ assert(!m->udev_device_monitor);
assert(!m->udev_vcsa_monitor);
assert(!m->udev_button_monitor);

@@ -1169,6 +1199,33 @@ static int manager_connect_udev(Manager *m) {
if (epoll_ctl(m->epoll_fd, EPOLL_CTL_ADD, m->udev_seat_fd, &ev) < 0)
return -errno;

+ m->udev_device_monitor = udev_monitor_new_from_netlink(m->udev, "udev");
+ if (!m->udev_device_monitor)
+ return -ENOMEM;
+
+ r = udev_monitor_filter_add_match_subsystem_devtype(m->udev_device_monitor, "input", NULL);
+ if (r < 0)
+ return r;
+
+ r = udev_monitor_filter_add_match_subsystem_devtype(m->udev_device_monitor, "graphics", NULL);
+ if (r < 0)
+ return r;
+
+ r = udev_monitor_filter_add_match_subsystem_devtype(m->udev_device_monitor, "drm", NULL);
+ if (r < 0)
+ return r;
+
+ r = udev_monitor_enable_receiving(m->udev_device_monitor);
+ if (r < 0)
+ return r;
+
+ m->udev_device_fd = udev_monitor_get_fd(m->udev_device_monitor);
+ zero(ev);
+ ev.events = EPOLLIN;
+ ev.data.u32 = FD_DEVICE_UDEV;
+ if (epoll_ctl(m->epoll_fd, EPOLL_CTL_ADD, m->udev_device_fd, &ev) < 0)
+ return -errno;
+
/* Don't watch keys if nobody cares */
if (m->handle_power_key != HANDLE_IGNORE ||
m->handle_suspend_key != HANDLE_IGNORE ||
@@ -1545,6 +1602,10 @@ int manager_run(Manager *m) {
manager_dispatch_seat_udev(m);
break;

+ case FD_DEVICE_UDEV:
+ manager_dispatch_device_udev(m);
+ break;
+
case FD_VCSA_UDEV:
manager_dispatch_vcsa_udev(m);
break;
diff --git a/src/login/logind.h b/src/login/logind.h
index e9838a8..1a97351 100644
--- a/src/login/logind.h
+++ b/src/login/logind.h
@@ -57,9 +57,10 @@ struct Manager {
LIST_HEAD(User, user_gc_queue);

struct udev *udev;
- struct udev_monitor *udev_seat_monitor, *udev_vcsa_monitor, *udev_button_monitor;
+ struct udev_monitor *udev_seat_monitor, *udev_device_monitor, *udev_vcsa_monitor, *udev_button_monitor;

int udev_seat_fd;
+ int udev_device_fd;
int udev_vcsa_fd;
int udev_button_fd;

@@ -121,6 +122,7 @@ struct Manager {

enum {
FD_SEAT_UDEV,
+ FD_DEVICE_UDEV,
FD_VCSA_UDEV,
FD_BUTTON_UDEV,
FD_CONSOLE,
@@ -132,7 +134,7 @@ enum {
Manager *manager_new(void);
void manager_free(Manager *m);

-int manager_add_device(Manager *m, const char *sysfs, Device **_device);
+int manager_add_device(Manager *m, const char *sysfs, bool master, Device **_device);
int manager_add_button(Manager *m, const char *name, Button **_button);
int manager_add_seat(Manager *m, const char *id, Seat **_seat);
int manager_add_session(Manager *m, const char *id, Session **_session);

--
1.8.4

David Herrmann

2013-09-17 15:39:55 UTC