WIP: rtkit support

meson_options.txt

@@ -192,6 +192,7 @@ option('solaris_output', type: 'feature', description: 'Solaris /dev/audio suppo
 #
 
 option('dbus', type: 'feature', description: 'D-Bus support')
+option('rtkit', type: 'feature', description: 'Use RealtimeKit for requesting realtime scheduling')
 option('expat', type: 'feature', description: 'Expat XML support')
 option('icu', type: 'feature', description: 'Use libicu for Unicode')
 option('iconv', type: 'feature', description: 'Use iconv() for character set conversion')

src/thread/Util.cxx

@@ -8,10 +8,206 @@
 #include <sched.h>
 #include <sys/syscall.h>
 #include <unistd.h>
+#include <dbus/dbus.h>
+#include <string.h>
+#include <sys/types.h>
+#include <errno.h>
 #elif defined(_WIN32)
 #include <windows.h>
 #endif
 
+
+#ifdef __linux__
+const char* RTKIT_SERVICE_NAME = "org.freedesktop.RealtimeKit1";
+const char* RTKIT_OBJECT_PATH = "/org/freedesktop/RealtimeKit1";
+
+// static int
+// rtkit_get_max_realtime_priority(DBusConnection &connection)
+// {
+//   // TODO: Implement this function
+//   DBusError error;
+// }
+
+// static void
+// rtkit_make_realtime(DBusConnection &connection, pid_t thread, int priority)
+// {
+//   // TODO: Implement this function
+
+// }
+#endif
+
+// TODO: minimize and drop
+#ifdef __linux__
+
+#define RTKIT_SERVICE_NAME "org.freedesktop.RealtimeKit1"
+#define RTKIT_OBJECT_PATH "/org/freedesktop/RealtimeKit1"
+
+static pid_t _gettid(void) {
+        return (pid_t) syscall(SYS_gettid);
+}
+
+static int translate_error(const char *name) {
+        if (strcmp(name, DBUS_ERROR_NO_MEMORY) == 0)
+                return -ENOMEM;
+        if (strcmp(name, DBUS_ERROR_SERVICE_UNKNOWN) == 0 ||
+            strcmp(name, DBUS_ERROR_NAME_HAS_NO_OWNER) == 0)
+                return -ENOENT;
+        if (strcmp(name, DBUS_ERROR_ACCESS_DENIED) == 0 ||
+            strcmp(name, DBUS_ERROR_AUTH_FAILED) == 0)
+                return -EACCES;
+
+        return -EIO;
+}
+
+static long long rtkit_get_int_property(DBusConnection *connection, const char* propname, long long* propval) {
+        DBusMessage *m = NULL, *r = NULL;
+        DBusMessageIter iter, subiter;
+        dbus_int64_t i64;
+        dbus_int32_t i32;
+        DBusError error;
+        int current_type;
+        long long ret;
+        const char * interfacestr = "org.freedesktop.RealtimeKit1";
+
+        dbus_error_init(&error);
+
+        if (!(m = dbus_message_new_method_call(
+                              RTKIT_SERVICE_NAME,
+                              RTKIT_OBJECT_PATH,
+                              "org.freedesktop.DBus.Properties",
+                              "Get"))) {
+                ret = -ENOMEM;
+                goto finish;
+        }
+
+        if (!dbus_message_append_args(
+                            m,
+                            DBUS_TYPE_STRING, &interfacestr,
+                            DBUS_TYPE_STRING, &propname,
+                            DBUS_TYPE_INVALID)) {
+                ret = -ENOMEM;
+                goto finish;
+        }
+
+        if (!(r = dbus_connection_send_with_reply_and_block(connection, m, -1, &error))) {
+                ret = translate_error(error.name);
+                goto finish;
+        }
+
+        if (dbus_set_error_from_message(&error, r)) {
+                ret = translate_error(error.name);
+                goto finish;
+        }
+
+        ret = -EBADMSG;
+        dbus_message_iter_init(r, &iter);
+        while ((current_type = dbus_message_iter_get_arg_type (&iter)) != DBUS_TYPE_INVALID) {
+
+                if (current_type == DBUS_TYPE_VARIANT) {
+                        dbus_message_iter_recurse(&iter, &subiter);
+
+                        while ((current_type = dbus_message_iter_get_arg_type (&subiter)) != DBUS_TYPE_INVALID) {
+
+                                if (current_type == DBUS_TYPE_INT32) {
+                                        dbus_message_iter_get_basic(&subiter, &i32);
+                                        *propval = i32;
+                                        ret = 0;
+                                }
+
+                                if (current_type == DBUS_TYPE_INT64) {
+                                        dbus_message_iter_get_basic(&subiter, &i64);
+                                        *propval = i64;
+                                        ret = 0;
+                                }
+
+                                dbus_message_iter_next (&subiter);
+                        }
+                }
+                dbus_message_iter_next (&iter);
+        }
+
+finish:
+
+        if (m)
+                dbus_message_unref(m);
+
+        if (r)
+                dbus_message_unref(r);
+
+        dbus_error_free(&error);
+
+        return ret;
+}
+
+static int rtkit_get_max_realtime_priority(DBusConnection *connection) {
+        long long retval;
+        int err;
+
+        err = rtkit_get_int_property(connection, "MaxRealtimePriority", &retval);
+        return err < 0 ? err : retval;
+}
+
+static int rtkit_make_realtime(DBusConnection *connection, pid_t thread, int priority) {
+        DBusMessage *m = NULL, *r = NULL;
+        dbus_uint64_t u64;
+        dbus_uint32_t u32;
+        DBusError error;
+        int ret;
+
+        dbus_error_init(&error);
+
+        if (thread == 0)
+                thread = _gettid();
+
+        if (!(m = dbus_message_new_method_call(
+                              RTKIT_SERVICE_NAME,
+                              RTKIT_OBJECT_PATH,
+                              "org.freedesktop.RealtimeKit1",
+                              "MakeThreadRealtime"))) {
+                ret = -ENOMEM;
+                goto finish;
+        }
+
+        u64 = (dbus_uint64_t) thread;
+        u32 = (dbus_uint32_t) priority;
+
+        if (!dbus_message_append_args(
+                            m,
+                            DBUS_TYPE_UINT64, &u64,
+                            DBUS_TYPE_UINT32, &u32,
+                            DBUS_TYPE_INVALID)) {
+                ret = -ENOMEM;
+                goto finish;
+        }
+
+        if (!(r = dbus_connection_send_with_reply_and_block(connection, m, -1, &error))) {
+                ret = translate_error(error.name);
+                goto finish;
+        }
+
+
+        if (dbus_set_error_from_message(&error, r)) {
+                ret = translate_error(error.name);
+                goto finish;
+        }
+
+        ret = 0;
+
+finish:
+
+        if (m)
+                dbus_message_unref(m);
+
+        if (r)
+                dbus_message_unref(r);
+
+        dbus_error_free(&error);
+
+        return ret;
+}
+
+#endif
+
 #ifdef __linux__
 
 #ifndef ANDROID
@@ -82,7 +278,39 @@ SetThreadRealtime()
 	policy |= SCHED_RESET_ON_FORK;
 #endif
 
-	if (linux_sched_setscheduler(0, policy, &sched_param) < 0)
+	int res = linux_sched_setscheduler(0, policy, &sched_param);
-		throw MakeErrno("sched_setscheduler failed");
+
+	if (res < 0 && errno == EPERM) {
+		DBusError error;
+		DBusConnection *system_bus;
+
+		if (!(system_bus = dbus_bus_get(DBUS_BUS_SYSTEM, &error))) {
+			throw MakeErrno("could not connect to dbus");
+    }
+
+		int max_realtime_priority;
+		if ((max_realtime_priority = rtkit_get_max_realtime_priority(system_bus)) < 0) {
+			dbus_connection_unref(system_bus);
+			throw MakeErrno("could not retrieve maximum realtime priority allowed");
+		}
+
+		if (max_realtime_priority < sched_param.sched_priority) {
+			dbus_connection_unref(system_bus);
+			throw MakeErrno("maximum realtime priority is below 40");
+		}
+
+    pid_t pid = getpid();
+		if (rtkit_make_realtime(system_bus, pid, sched_param.sched_priority) < 0) {
+			dbus_connection_unref(system_bus);
+			throw MakeErrno("failed to request realtime scheduling");
+		}
+
+		dbus_connection_unref(system_bus);
+		res = 0;
+	}
+
+	// if (res < 0) {
+	// 	throw MakeErrno("sched_setscheduler failed");
+	// }
 #endif	// __linux__
 }

src/thread/meson.build

@@ -7,6 +7,13 @@ else
   threads_dep = dependency('threads')
 endif
 
+if is_linux
+  dbus_dep = dependency('dbus-1', required: get_option('dbus'))
+  conf.set('ENABLE_DBUS', dbus_dep.found())
+else
+  dbus_dep = []
+endif
+
 conf.set('HAVE_PTHREAD_SETNAME_NP', compiler.has_function('pthread_setname_np', dependencies: threads_dep))
 
 thread = static_library(
@@ -16,6 +23,7 @@ thread = static_library(
   include_directories: inc,
   dependencies: [
     threads_dep,
+    dbus_dep,
   ],
 )