core: add bus calls for determining jobs waiting for other jobs

This should make it easier to debug job deadlocks.

6 files changed, 221 insertions, 0 deletions

diff --git a/src/core/dbus-job.c b/src/core/dbus-job.c
index 7888c163f1..087a08dc0d 100644
--- a/src/core/dbus-job.c
+++ b/src/core/dbus-job.c
@@ -80,9 +80,61 @@ int bus_job_method_cancel(sd_bus_message *message, void *userdata, sd_bus_error
         return sd_bus_reply_method_return(message, NULL);
 }
 
+int bus_job_method_get_waiting_jobs(sd_bus_message *message, void *userdata, sd_bus_error *error) {
+        _cleanup_(sd_bus_message_unrefp) sd_bus_message *reply = NULL;
+        _cleanup_free_ Job **list = NULL;
+        Job *j = userdata;
+        int r, i, n;
+
+        if (strstr(sd_bus_message_get_member(message), "After"))
+                n = job_get_after(j, &list);
+        else
+                n = job_get_before(j, &list);
+        if (n < 0)
+                return n;
+
+        r = sd_bus_message_new_method_return(message, &reply);
+        if (r < 0)
+                return r;
+
+        r = sd_bus_message_open_container(reply, 'a', "(usssoo)");
+        if (r < 0)
+                return r;
+
+        for (i = 0; i < n; i ++) {
+                _cleanup_free_ char *unit_path = NULL, *job_path = NULL;
+
+                job_path = job_dbus_path(list[i]);
+                if (!job_path)
+                        return -ENOMEM;
+
+                unit_path = unit_dbus_path(list[i]->unit);
+                if (!unit_path)
+                        return -ENOMEM;
+
+                r = sd_bus_message_append(reply, "(usssoo)",
+                                          list[i]->id,
+                                          list[i]->unit->id,
+                                          job_type_to_string(list[i]->type),
+                                          job_state_to_string(list[i]->state),
+                                          job_path,
+                                          unit_path);
+                if (r < 0)
+                        return r;
+        }
+
+        r = sd_bus_message_close_container(reply);
+        if (r < 0)
+                return r;
+
+        return sd_bus_send(NULL, reply, NULL);
+}
+
 const sd_bus_vtable bus_job_vtable[] = {
         SD_BUS_VTABLE_START(0),
         SD_BUS_METHOD("Cancel", NULL, NULL, bus_job_method_cancel, SD_BUS_VTABLE_UNPRIVILEGED),
+        SD_BUS_METHOD("GetAfter", NULL, "a(usssoo)", bus_job_method_get_waiting_jobs, SD_BUS_VTABLE_UNPRIVILEGED),
+        SD_BUS_METHOD("GetBefore", NULL, "a(usssoo)", bus_job_method_get_waiting_jobs, SD_BUS_VTABLE_UNPRIVILEGED),
         SD_BUS_PROPERTY("Id", "u", NULL, offsetof(Job, id), SD_BUS_VTABLE_PROPERTY_CONST),
         SD_BUS_PROPERTY("Unit", "(so)", property_get_unit, 0, SD_BUS_VTABLE_PROPERTY_CONST),
         SD_BUS_PROPERTY("JobType", "s", property_get_type, offsetof(Job, type), SD_BUS_VTABLE_PROPERTY_CONST),
diff --git a/src/core/dbus-job.h b/src/core/dbus-job.h
index f9148895be..a4366a0720 100644
--- a/src/core/dbus-job.h
+++ b/src/core/dbus-job.h
@@ -26,6 +26,7 @@
 extern const sd_bus_vtable bus_job_vtable[];
 
 int bus_job_method_cancel(sd_bus_message *message, void *job, sd_bus_error *error);
+int bus_job_method_get_waiting_jobs(sd_bus_message *message, void *userdata, sd_bus_error *error);
 
 void bus_job_send_change_signal(Job *j);
 void bus_job_send_removed_signal(Job *j);
diff --git a/src/core/dbus-manager.c b/src/core/dbus-manager.c
index 5a7922a249..9af49dd1bc 100644
--- a/src/core/dbus-manager.c
+++ b/src/core/dbus-manager.c
@@ -2285,6 +2285,26 @@ static int method_get_unit_file_links(sd_bus_message *message, void *userdata, s
         return sd_bus_send(NULL, reply, NULL);
 }
 
+static int method_get_job_waiting(sd_bus_message *message, void *userdata, sd_bus_error *error) {
+        Manager *m = userdata;
+        uint32_t id;
+        Job *j;
+        int r;
+
+        assert(message);
+        assert(m);
+
+        r = sd_bus_message_read(message, "u", &id);
+        if (r < 0)
+                return r;
+
+        j = manager_get_job(m, id);
+        if (!j)
+                return sd_bus_error_setf(error, BUS_ERROR_NO_SUCH_JOB, "Job %u does not exist.", (unsigned) id);
+
+        return bus_job_method_get_waiting_jobs(message, j, error);
+}
+
 const sd_bus_vtable bus_manager_vtable[] = {
         SD_BUS_VTABLE_START(0),
 
@@ -2390,6 +2410,8 @@ const sd_bus_vtable bus_manager_vtable[] = {
         SD_BUS_METHOD("StartTransientUnit", "ssa(sv)a(sa(sv))", "o", method_start_transient_unit, SD_BUS_VTABLE_UNPRIVILEGED),
         SD_BUS_METHOD("GetUnitProcesses", "s", "a(sus)", method_get_unit_processes, SD_BUS_VTABLE_UNPRIVILEGED),
         SD_BUS_METHOD("GetJob", "u", "o", method_get_job, SD_BUS_VTABLE_UNPRIVILEGED),
+        SD_BUS_METHOD("GetJobAfter", "u", "a(usssoo)", method_get_job_waiting, SD_BUS_VTABLE_UNPRIVILEGED),
+        SD_BUS_METHOD("GetJobBefore", "u", "a(usssoo)", method_get_job_waiting, SD_BUS_VTABLE_UNPRIVILEGED),
         SD_BUS_METHOD("CancelJob", "u", NULL, method_cancel_job, SD_BUS_VTABLE_UNPRIVILEGED),
         SD_BUS_METHOD("ClearJobs", NULL, NULL, method_clear_jobs, SD_BUS_VTABLE_UNPRIVILEGED),
         SD_BUS_METHOD("ResetFailed", NULL, NULL, method_reset_failed, SD_BUS_VTABLE_UNPRIVILEGED),
diff --git a/src/core/job.c b/src/core/job.c
index d6e71d68ef..2ba4c78096 100644
--- a/src/core/job.c
+++ b/src/core/job.c
@@ -1306,6 +1306,133 @@ void job_add_to_gc_queue(Job *j) {
         j->in_gc_queue = true;
 }
 
+static int job_compare(const void *a, const void *b) {
+        Job *x = *(Job**) a, *y = *(Job**) b;
+
+        if (x->id < y->id)
+                return -1;
+        if (x->id > y->id)
+                return 1;
+
+        return 0;
+}
+
+static size_t sort_job_list(Job **list, size_t n) {
+        Job *previous = NULL;
+        size_t a, b;
+
+        /* Order by numeric IDs */
+        qsort_safe(list, n, sizeof(Job*), job_compare);
+
+        /* Filter out duplicates */
+        for (a = 0, b = 0; a < n; a++) {
+
+                if (previous == list[a])
+                        continue;
+
+                previous = list[b++] = list[a];
+        }
+
+        return b;
+}
+
+int job_get_before(Job *j, Job*** ret) {
+        _cleanup_free_ Job** list = NULL;
+        size_t n = 0, n_allocated = 0;
+        Unit *other = NULL;
+        Iterator i;
+
+        /* Returns a list of all pending jobs that need to finish before this job may be started. */
+
+        assert(j);
+        assert(ret);
+
+        if (j->ignore_order) {
+                *ret = NULL;
+                return 0;
+        }
+
+        if (IN_SET(j->type, JOB_START, JOB_VERIFY_ACTIVE, JOB_RELOAD)) {
+
+                SET_FOREACH(other, j->unit->dependencies[UNIT_AFTER], i) {
+                        if (!other->job)
+                                continue;
+
+                        if (!GREEDY_REALLOC(list, n_allocated, n+1))
+                                return -ENOMEM;
+                        list[n++] = other->job;
+                }
+        }
+
+        SET_FOREACH(other, j->unit->dependencies[UNIT_BEFORE], i) {
+                if (!other->job)
+                        continue;
+
+                if (!IN_SET(other->job->type, JOB_STOP, JOB_RESTART))
+                        continue;
+
+                if (!GREEDY_REALLOC(list, n_allocated, n+1))
+                        return -ENOMEM;
+                list[n++] = other->job;
+        }
+
+        n = sort_job_list(list, n);
+
+        *ret = list;
+        list = NULL;
+
+        return (int) n;
+}
+
+int job_get_after(Job *j, Job*** ret) {
+        _cleanup_free_ Job** list = NULL;
+        size_t n = 0, n_allocated = 0;
+        Unit *other = NULL;
+        Iterator i;
+
+        assert(j);
+        assert(ret);
+
+        /* Returns a list of all pending jobs that are waiting for this job to finish. */
+
+        SET_FOREACH(other, j->unit->dependencies[UNIT_BEFORE], i) {
+                if (!other->job)
+                        continue;
+
+                if (other->job->ignore_order)
+                        continue;
+
+                if (!IN_SET(other->job->type, JOB_START, JOB_VERIFY_ACTIVE, JOB_RELOAD))
+                        continue;
+
+                if (!GREEDY_REALLOC(list, n_allocated, n+1))
+                        return -ENOMEM;
+                list[n++] = other->job;
+        }
+
+        if (IN_SET(j->type, JOB_STOP, JOB_RESTART)) {
+
+                SET_FOREACH(other, j->unit->dependencies[UNIT_AFTER], i) {
+                        if (!other->job)
+                                continue;
+
+                        if (other->job->ignore_order)
+                                continue;
+
+                        if (!GREEDY_REALLOC(list, n_allocated, n+1))
+                                return -ENOMEM;
+                        list[n++] = other->job;
+                }
+        }
+
+        n = sort_job_list(list, n);
+
+        *ret = list;
+        list = NULL;
+
+        return (int) n;
+}
+
 static const char* const job_state_table[_JOB_STATE_MAX] = {
         [JOB_WAITING] = "waiting",
         [JOB_RUNNING] = "running",
diff --git a/src/core/job.h b/src/core/job.h
index 6fdec9f226..bea743f462 100644
--- a/src/core/job.h
+++ b/src/core/job.h
@@ -234,6 +234,9 @@ int job_get_timeout(Job *j, usec_t *timeout) _pure_;
 bool job_check_gc(Job *j);
 void job_add_to_gc_queue(Job *j);
 
+int job_get_before(Job *j, Job*** ret);
+int job_get_after(Job *j, Job*** ret);
+
 const char* job_type_to_string(JobType t) _const_;
 JobType job_type_from_string(const char *s) _pure_;
 
diff --git a/src/core/org.freedesktop.systemd1.conf b/src/core/org.freedesktop.systemd1.conf
index a61677e645..e824a2233c 100644
--- a/src/core/org.freedesktop.systemd1.conf
+++ b/src/core/org.freedesktop.systemd1.conf
@@ -66,6 +66,14 @@
 
                 <allow send_destination="org.freedesktop.systemd1"
                        send_interface="org.freedesktop.systemd1.Manager"
+                       send_member="GetJobAfter"/>
+
+                <allow send_destination="org.freedesktop.systemd1"
+                       send_interface="org.freedesktop.systemd1.Manager"
+                       send_member="GetJobBefore"/>
+
+                <allow send_destination="org.freedesktop.systemd1"
+                       send_interface="org.freedesktop.systemd1.Manager"
                        send_member="ListUnits"/>
 
                 <allow send_destination="org.freedesktop.systemd1"
@@ -250,6 +258,14 @@
                        send_interface="org.freedesktop.systemd1.Job"
                        send_member="Cancel"/>
 
+                <allow send_destination="org.freedesktop.systemd1"
+                       send_interface="org.freedesktop.systemd1.Job"
+                       send_member="GetAfter"/>
+
+                <allow send_destination="org.freedesktop.systemd1"
+                       send_interface="org.freedesktop.systemd1.Job"
+                       send_member="GetBefore"/>
+
                 <allow receive_sender="org.freedesktop.systemd1"/>
         </policy>