Classify processes from sessions into cgroups

Create a private cgroup tree associated with no controllers, and use it
to map PIDs to sessions.  Since we use our own path structure, remove
internal cgroup-related helpers that interpret the cgroup path structure
to pull out users, slices, and scopes.

4 files changed, 136 insertions, 14 deletions

diff --git a/src/login/logind-core.c b/src/login/logind-core.c
index 67b03623ac..041593c5ab 100644
--- a/src/login/logind-core.c
+++ b/src/login/logind-core.c
@@ -311,24 +311,41 @@ int manager_process_button_device(Manager *m, struct udev_device *d) {
 }
 
 int manager_get_session_by_pid(Manager *m, pid_t pid, Session **session) {
+        _cleanup_free_ char *session_name = NULL;
+        Session *s;
+        int r;
+
         assert(m);
         assert(session);
 
-        /* Without cgroups, we have no way to map from pid to
-           session.  */
-        return 0;
+        if (pid < 1)
+                return -EINVAL;
+
+        r = cg_pid_get_session(pid, &session_name);
+        if (r < 0)
+                return 0;
+
+        s = hashmap_get(m->sessions, session_name);
+        if (!s)
+                return 0;
+
+        *session = s;
+        return 1;
 }
 
 int manager_get_user_by_pid(Manager *m, pid_t pid, User **user) {
+        Session *s;
+        int r;
+
         assert(m);
         assert(user);
 
-        if (pid < 1)
-                return -EINVAL;
+        r = manager_get_session_by_pid (m, pid, &s);
+        if (r <= 0)
+                return r;
 
-        /* Without cgroups, we have no way to map from pid to
-           user.  */
-        return 0;
+        *user = s->user;
+        return 1;
 }
 
 int manager_get_idle_hint(Manager *m, dual_timestamp *t) {
diff --git a/src/login/logind-session.c b/src/login/logind-session.c
index 109e3ef133..f03c2e565d 100644
--- a/src/login/logind-session.c
+++ b/src/login/logind-session.c
@@ -36,6 +36,8 @@
 #include "audit.h"
 #include "bus-util.h"
 #include "bus-error.h"
+#include "cgroup-util.h"
+#include "def.h"
 #include "logind-session.h"
 
 static void session_remove_fifo(Session *s);
@@ -475,6 +477,25 @@ int session_activate(Session *s) {
         return 0;
 }
 
+static int session_start_cgroup(Session *s) {
+        int r;
+
+        assert(s);
+        assert(s->user);
+        assert(s->leader > 0);
+
+        /* First, create our own group */
+        r = cg_create(SYSTEMD_CGROUP_CONTROLLER, s->id);
+        if (r < 0)
+                return log_error_errno(r, "Failed to create cgroup %s: %m", s->id);
+
+        r = cg_attach(SYSTEMD_CGROUP_CONTROLLER, s->id, s->leader);
+        if (r < 0)
+                log_warning_errno(r, "Failed to attach PID %d to cgroup %s: %m", s->leader, s->id);
+
+        return 0;
+}
+
 int session_start(Session *s) {
         int r;
 
@@ -490,6 +511,10 @@ int session_start(Session *s) {
         if (r < 0)
                 return r;
 
+        r = session_start_cgroup(s);
+        if (r < 0)
+                return r;
+
         log_struct(s->class == SESSION_BACKGROUND ? LOG_DEBUG : LOG_INFO,
                    LOG_MESSAGE_ID(SD_MESSAGE_SESSION_START),
                    "SESSION_ID=%s", s->id,
@@ -527,8 +552,23 @@ int session_start(Session *s) {
         return 0;
 }
 
+static int session_stop_cgroup(Session *s, bool force) {
+        _cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;
+        int r;
+
+        assert(s);
+
+        if (force || manager_shall_kill(s->manager, s->user->name)) {
+                r = session_kill(s, KILL_ALL, SIGTERM);
+                if (r < 0)
+                        return r;
+        }
+
+        return 0;
+}
+
 int session_stop(Session *s, bool force) {
-        int r = 0;
+        int r;
 
         assert(s);
 
@@ -540,6 +580,9 @@ int session_stop(Session *s, bool force) {
         /* We are going down, don't care about FIFOs anymore */
         session_remove_fifo(s);
 
+        /* Kill cgroup */
+        r = session_stop_cgroup(s, force);
+
         s->stopping = true;
 
         user_elect_display(s->user);
@@ -609,7 +652,7 @@ int session_release(Session *s) {
         /* In systemd, session release is triggered by user jobs
            dying.  In elogind we don't have that so go ahead and stop
            now.  */
-        session_stop(s, false);
+        return session_stop(s, false);
 }
 
 bool session_is_active(Session *s) {
@@ -814,6 +857,9 @@ bool session_check_gc(Session *s, bool drop_not_started) {
                         return true;
         }
 
+        if (cg_is_empty_recursive (SYSTEMD_CGROUP_CONTROLLER, s->id, false) > 0)
+                return true;
+
         return false;
 }
 
@@ -846,8 +892,23 @@ SessionState session_get_state(Session *s) {
 int session_kill(Session *s, KillWho who, int signo) {
         assert(s);
 
-        /* No way to kill the session without cgroups.  */
-        return -ESRCH;
+        if (who == KILL_LEADER) {
+                if (s->leader <= 0)
+                        return -ESRCH;
+
+                /* FIXME: verify that leader is in cgroup?  */
+
+                if (kill(s->leader, signo) < 0) {
+                        return log_error_errno(errno, "Failed to kill process leader %d for session %s: %m", s->leader, s->id);
+                }
+                return 0;
+        } else {
+                bool sigcont = false;
+                bool ignore_self = true;
+                bool rem = true;
+                return cg_kill_recursive (SYSTEMD_CGROUP_CONTROLLER, s->id, signo,
+                                          sigcont, ignore_self, rem, NULL);
+        }
 }
 
 static int session_open_vt(Session *s) {
diff --git a/src/login/logind-user.c b/src/login/logind-user.c
index 539c316ad6..0aac3bcf52 100644
--- a/src/login/logind-user.c
+++ b/src/login/logind-user.c
@@ -562,10 +562,18 @@ UserState user_get_state(User *u) {
 }
 
 int user_kill(User *u, int signo) {
+        Session *s;
+        int res = 0;
+
         assert(u);
 
-        /* FIXME: No way to kill a user without systemd.  */
-        return -ESRCH;
+        LIST_FOREACH(sessions_by_user, s, u->sessions) {
+                int r = session_kill(s, KILL_ALL, signo);
+                if (res == 0 && r < 0)
+                        res = r;
+        }
+
+        return res;
 }
 
 void user_elect_display(User *u) {
diff --git a/src/login/logind.c b/src/login/logind.c
index 49dae036c4..8e8fe19157 100644
--- a/src/login/logind.c
+++ b/src/login/logind.c
@@ -542,6 +542,35 @@ static int manager_dispatch_console(sd_event_source *s, int fd, uint32_t revents
         return 0;
 }
 
+static int signal_agent_released(sd_bus *bus, sd_bus_message *message, void *userdata, sd_bus_error *error) {
+        Manager *m = userdata;
+        Session *s;
+        const char *cgroup;
+        int r;
+
+        assert(bus);
+        assert(message);
+        assert(m);
+
+        r = sd_bus_message_read(message, "s", &cgroup);
+        if (r < 0) {
+                bus_log_parse_error(r);
+                return 0;
+        }
+
+        s = hashmap_get(m->sessions, cgroup);
+
+        if (!s) {
+                log_warning("Session not found: %s", cgroup);
+                return 0;
+        }
+
+        session_finalize(s);
+        session_free(s);
+
+        return 0;
+}
+
 static int manager_connect_bus(Manager *m) {
         _cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;
         int r;
@@ -557,6 +586,13 @@ static int manager_connect_bus(Manager *m) {
         if (r < 0)
                 return log_error_errno(r, "Failed to add manager object vtable: %m");
 
+        r = sd_bus_add_match(m->bus, NULL,
+                             "type='signal',"
+                             "interface='org.freedesktop.systemd1.Agent',"
+                             "member='Released',"
+                             "path='/org/freedesktop/systemd1/agent'",
+                             signal_agent_released, m);
+
         r = sd_bus_add_fallback_vtable(m->bus, NULL, "/org/freedesktop/login1/seat", "org.freedesktop.login1.Seat", seat_vtable, seat_object_find, m);
         if (r < 0)
                 return log_error_errno(r, "Failed to add seat object vtable: %m");