[sysprof] governor: add daemon API and helpers to set CPU governor

[Christian Hergert <chergert src gnome org>]

commit fc745767d4a04c15d829c359653fa5b75ef21584
Author: Christian Hergert <chergert redhat com>
Date:   Fri Jun 14 08:03:37 2019 -0700

    governor: add daemon API and helpers to set CPU governor

 src/libsysprof/sysprof-helpers.c   |  66 ++++++++++++++++++++++
 src/libsysprof/sysprof-helpers.h   |   9 +++
 src/org.gnome.Sysprof3.Service.xml |  12 ++++
 src/sysprofd/ipc-service-impl.c    | 112 +++++++++++++++++++++++++++++++++++++
 4 files changed, 199 insertions(+)
---
diff --git a/src/libsysprof/sysprof-helpers.c b/src/libsysprof/sysprof-helpers.c
index a98245b..4ba3dd0 100644
--- a/src/libsysprof/sysprof-helpers.c
+++ b/src/libsysprof/sysprof-helpers.c
@@ -671,3 +671,69 @@ sysprof_helpers_get_process_info_finish (SysprofHelpers  *self,
 
   return FALSE;
 }
+
+static void
+sysprof_helpers_set_governor_cb (GObject      *object,
+                                 GAsyncResult *result,
+                                 gpointer      user_data)
+{
+  IpcService *proxy = (IpcService *)object;
+  g_autoptr(GError) error = NULL;
+  g_autoptr(GTask) task = user_data;
+  gchar *old_governor = NULL;
+
+  g_assert (IPC_IS_SERVICE (proxy));
+  g_assert (G_IS_ASYNC_RESULT (result));
+  g_assert (G_IS_TASK (task));
+
+  if (!ipc_service_call_set_governor_finish (proxy, &old_governor, result, &error))
+    g_task_return_error (task, g_steal_pointer (&error));
+  else
+    g_task_return_pointer (task, old_governor, g_free);
+}
+
+void
+sysprof_helpers_set_governor_async (SysprofHelpers      *self,
+                                    const gchar         *governor,
+                                    GCancellable        *cancellable,
+                                    GAsyncReadyCallback  callback,
+                                    gpointer             user_data)
+{
+  g_autoptr(GTask) task = NULL;
+
+  g_return_if_fail (SYSPROF_IS_HELPERS (self));
+  g_return_if_fail (governor != NULL);
+
+  task = g_task_new (self, cancellable, callback, user_data);
+  g_task_set_source_tag (task, sysprof_helpers_set_governor_async);
+
+  if (fail_if_no_proxy (self, task))
+    return;
+
+  ipc_service_call_set_governor (self->proxy,
+                                 governor,
+                                 cancellable,
+                                 sysprof_helpers_set_governor_cb,
+                                 g_steal_pointer (&task));
+}
+
+gboolean
+sysprof_helpers_set_governor_finish (SysprofHelpers  *self,
+                                     GAsyncResult    *result,
+                                     gchar          **old_governer,
+                                     GError         **error)
+{
+  g_autofree gchar *ret = NULL;
+
+  g_return_val_if_fail (SYSPROF_IS_HELPERS (self), FALSE);
+  g_return_val_if_fail (G_IS_TASK (result), FALSE);
+
+  if ((ret = g_task_propagate_pointer (G_TASK (result), error)))
+    {
+      if (old_governer != NULL)
+        *old_governer = g_steal_pointer (&ret);
+      return TRUE;
+    }
+
+  return FALSE;
+}
diff --git a/src/libsysprof/sysprof-helpers.h b/src/libsysprof/sysprof-helpers.h
index 3cce84a..9f50a8f 100644
--- a/src/libsysprof/sysprof-helpers.h
+++ b/src/libsysprof/sysprof-helpers.h
@@ -99,5 +99,14 @@ gboolean        sysprof_helpers_perf_event_open        (SysprofHelpers
                                                         gint                    *out_fd,
                                                         GError                 **error);
 #endif
+void            sysprof_helpers_set_governor_async     (SysprofHelpers          *self,
+                                                        const gchar             *governor,
+                                                        GCancellable            *cancellable,
+                                                        GAsyncReadyCallback      callback,
+                                                        gpointer                 user_data);
+gboolean        sysprof_helpers_set_governor_finish    (SysprofHelpers          *self,
+                                                        GAsyncResult            *result,
+                                                        gchar                  **old_governor,
+                                                        GError                 **error);
 
 G_END_DECLS
diff --git a/src/org.gnome.Sysprof3.Service.xml b/src/org.gnome.Sysprof3.Service.xml
index 6b57679..70a83ae 100644
--- a/src/org.gnome.Sysprof3.Service.xml
+++ b/src/org.gnome.Sysprof3.Service.xml
@@ -92,5 +92,17 @@
       <arg name="attributes" type="s" direction="in"/>
       <arg name="processes" type="aa{sv}" direction="out"/>
     </method>
+
+    <!--
+      SetGovernor:
+      @governor: the new governor to use (such as "performance").
+      @old_governor: the governor that was in use before setting
+
+      Sets the CPU governor to be used on the system.
+    -->
+    <method name="SetGovernor">
+      <arg name="governor" type="s" direction="in"/>
+      <arg name="old_governor" type="s" direction="out"/>
+    </method>
   </interface>
 </node>
diff --git a/src/sysprofd/ipc-service-impl.c b/src/sysprofd/ipc-service-impl.c
index 3b668ab..db2d0f1 100644
--- a/src/sysprofd/ipc-service-impl.c
+++ b/src/sysprofd/ipc-service-impl.c
@@ -46,6 +46,54 @@ enum {
 
 static guint signals [N_SIGNALS];
 
+static gboolean
+file_set_contents_no_backup (const gchar  *path,
+                             const gchar  *contents,
+                             gssize        len,
+                             GError      **error)
+{
+  int fd;
+
+  g_return_val_if_fail (path != NULL, FALSE);
+
+  if (contents == NULL)
+    contents = "";
+
+  if (len < 0)
+    len = strlen (contents);
+
+  /* This is only for setting files in /sys, which need to be a single
+   * write anyway, so don't try to incrementally write at all.
+   */
+
+  fd = open (path, O_WRONLY, 0644);
+
+  if (fd == -1)
+    {
+      int errsv = errno;
+      g_set_error (error,
+                   G_FILE_ERROR,
+                   g_file_error_from_errno (errsv),
+                   "%s", g_strerror (errsv));
+      return FALSE;
+    }
+
+  if (write (fd, contents, len) != len)
+    {
+      int errsv = errno;
+      g_set_error (error,
+                   G_FILE_ERROR,
+                   g_file_error_from_errno (errsv),
+                   "%s", g_strerror (errsv));
+      close (fd);
+      return FALSE;
+    }
+
+  close (fd);
+
+  return TRUE;
+}
+
 static gboolean
 ipc_service_impl_handle_list_processes (IpcService            *service,
                                         GDBusMethodInvocation *invocation)
@@ -263,6 +311,69 @@ ipc_service_impl_handle_get_process_info (IpcService            *service,
   return TRUE;
 }
 
+static gboolean
+ipc_service_impl_handle_set_governor (IpcService            *service,
+                                      GDBusMethodInvocation *invocation,
+                                      const gchar           *governor)
+{
+  g_autoptr(GVariant) res = NULL;
+  g_autofree gchar *available = NULL;
+  g_autofree gchar *previous = NULL;
+  gboolean had_error = FALSE;
+  guint n_procs;
+
+  g_assert (IPC_IS_SERVICE (service));
+  g_assert (G_IS_DBUS_METHOD_INVOCATION (invocation));
+  g_assert (governor != NULL);
+
+  if (!g_file_get_contents ("/sys/devices/system/cpu/cpu0/cpufreq/scaling_available_governors", &available, 
NULL, NULL))
+    {
+      g_warning ("Failed to discover available governors");
+      had_error = TRUE;
+      goto finish;
+    }
+
+  if (strstr (available, governor) == NULL)
+    {
+      /* No such governor */
+      g_warning ("No such governor \"%s\"", governor);
+      had_error = TRUE;
+      goto finish;
+    }
+
+  if (g_file_get_contents ("/sys/devices/system/cpu/cpu0/cpufreq/scaling_governor", &previous, NULL, NULL))
+    g_strstrip (previous);
+  else
+    previous = g_strdup ("unknown");
+
+  n_procs = g_get_num_processors ();
+
+  for (guint i = 0; i < n_procs; i++)
+    {
+      g_autofree gchar *path = g_strdup_printf ("/sys/devices/system/cpu/cpu%u/cpufreq/scaling_governor", i);
+      g_autoptr(GError) error = NULL;
+
+      if (!file_set_contents_no_backup (path, governor, -1, &error))
+        {
+          g_warning ("Failed to set governor on CPU %u: %s", i, error->message);
+          had_error = TRUE;
+        }
+    }
+
+finish:
+  if (had_error)
+    g_dbus_method_invocation_return_error (g_steal_pointer (&invocation),
+                                           G_DBUS_ERROR,
+                                           G_DBUS_ERROR_FAILED,
+                                           "Failed to set governor");
+  else
+    ipc_service_complete_set_governor (service,
+                                       g_steal_pointer (&invocation),
+                                       previous);
+
+  return TRUE;
+}
+
 static void
 init_service_iface (IpcServiceIface *iface)
 {
@@ -271,6 +382,7 @@ init_service_iface (IpcServiceIface *iface)
   iface->handle_get_proc_fd = ipc_service_impl_handle_get_proc_fd;
   iface->handle_perf_event_open = ipc_service_impl_handle_perf_event_open;
   iface->handle_get_process_info = ipc_service_impl_handle_get_process_info;
+  iface->handle_set_governor = ipc_service_impl_handle_set_governor;
 }
 
 G_DEFINE_TYPE_WITH_CODE (IpcServiceImpl, ipc_service_impl, IPC_TYPE_SERVICE_SKELETON,