4 files changed, 143 insertions, 0 deletions
diff --git a/core/java/android/content/Context.java b/core/java/android/content/Context.java
index 36638f9..381daa3 100644
--- a/core/java/android/content/Context.java
+++ b/core/java/android/content/Context.java
@@ -1928,6 +1928,17 @@ public abstract class Context {
     public static final String INPUT_SERVICE = "input";
 
     /**
+     * Use with {@link #getSystemService} to retrieve a
+     * {@link android.os.SchedulingPolicyService} for managing scheduling policy.
+     *
+     * @see #getSystemService
+     * @see android.os.SchedulingPolicyService
+     *
+     * @hide
+     */
+    public static final String SCHEDULING_POLICY_SERVICE = "scheduling_policy";
+
+    /**
      * Determine whether the given permission is allowed for a particular
      * process and user ID running in the system.
      *
diff --git a/core/java/android/os/ISchedulingPolicyService.aidl b/core/java/android/os/ISchedulingPolicyService.aidl
new file mode 100644
index 0000000..1273c83
--- /dev/null
+++ b/core/java/android/os/ISchedulingPolicyService.aidl
@@ -0,0 +1,34 @@
+/*
+ * Copyright (C) 2012 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.os;
+
+/**
+ * Initially only provides requestPriority() below, but in longer term
+ * other scheduling policy related services will be collected here.
+ *
+ * @hide
+ */
+interface ISchedulingPolicyService {
+
+    /**
+     * Move thread tid into appropriate cgroup and assign it priority prio.
+     * The thread group leader of tid must be pid.
+     * There may be restrictions on who can call this.
+     */
+    int requestPriority(int pid, int tid, int prio);
+
+}
diff --git a/core/java/android/os/Process.java b/core/java/android/os/Process.java
index 8e041bb..0ba7b88 100644
--- a/core/java/android/os/Process.java
+++ b/core/java/android/os/Process.java
@@ -299,6 +299,24 @@ public class Process {
      **/
     private static final int THREAD_GROUP_FOREGROUND = 1;
 
+    /**
+     * System thread group.
+     * @hide
+     **/
+    public static final int THREAD_GROUP_SYSTEM = 2;
+
+    /**
+     * Application audio thread group.
+     * @hide
+     **/
+    public static final int THREAD_GROUP_AUDIO_APP = 3;
+
+    /**
+     * System audio thread group.
+     * @hide
+     **/
+    public static final int THREAD_GROUP_AUDIO_SYS = 4;
+
     public static final int SIGNAL_QUIT = 3;
     public static final int SIGNAL_KILL = 9;
     public static final int SIGNAL_USR1 = 10;
@@ -658,6 +676,21 @@ public class Process {
     }
 
     /**
+     * Returns the thread group leader id for a currently running thread.
+     * @param tid the thread id
+     * @return the thread group leader id of the thread, or -1 if the thread is not running.
+     *         This is same as what getpid(2) would return if called by tid.
+     * @hide
+     */
+    public static final int getThreadGroupLeader(int tid) {
+        String[] procStatusLabels = { "Tgid:" };
+        long[] procStatusValues = new long[1];
+        procStatusValues[0] = -1;
+        Process.readProcLines("/proc/" + tid + "/status", procStatusLabels, procStatusValues);
+        return (int) procStatusValues[0];
+    }
+
+    /**
      * Set the priority of a thread, based on Linux priorities.
      * 
      * @param tid The identifier of the thread/process to change.
diff --git a/core/java/android/os/SchedulingPolicyService.java b/core/java/android/os/SchedulingPolicyService.java
new file mode 100644
index 0000000..94f907b
--- /dev/null
+++ b/core/java/android/os/SchedulingPolicyService.java
@@ -0,0 +1,65 @@
+/*
+ * Copyright (C) 2012 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.os;
+
+import android.content.Context;
+import android.content.pm.PackageManager;
+import android.os.Binder;
+import android.os.Process;
+import android.util.Log;
+
+/**
+ * The implementation of the scheduling policy service interface.
+ *
+ * @hide
+ */
+public class SchedulingPolicyService extends ISchedulingPolicyService.Stub {
+
+    private static final String TAG = "SchedulingPolicyService";
+
+    // Minimum and maximum values allowed for requestPriority parameter prio
+    private static final int PRIORITY_MIN = 1;
+    private static final int PRIORITY_MAX = 2;
+
+    public SchedulingPolicyService() {
+    }
+
+    public int requestPriority(int pid, int tid, int prio) {
+        //Log.i(TAG, "requestPriority(pid=" + pid + ", tid=" + tid + ", prio=" + prio + ")");
+
+        // Verify that caller is mediaserver, priority is in range, and that the
+        // callback thread specified by app belongs to the app that called mediaserver.
+        // Once we've verified that the caller is mediaserver, we can trust the pid but
+        // we can't trust the tid.  No need to explicitly check for pid == 0 || tid == 0,
+        // since if not the case then the getThreadGroupLeader() test will also fail.
+        if (Binder.getCallingUid() != Process.MEDIA_UID || prio < PRIORITY_MIN ||
+                prio > PRIORITY_MAX || Process.getThreadGroupLeader(tid) != pid) {
+            return PackageManager.PERMISSION_DENIED;
+        }
+        try {
+            // make good use of our CAP_SYS_NICE capability
+            Process.setThreadGroup(tid, Binder.getCallingPid() == pid ?
+                    Process.THREAD_GROUP_AUDIO_SYS : Process.THREAD_GROUP_AUDIO_APP);
+            // must be in this order or it fails the schedulability constraint
+            Process.setThreadScheduler(tid, Process.SCHED_FIFO, prio);
+        } catch (RuntimeException e) {
+            return PackageManager.PERMISSION_DENIED;
+        }
+        return PackageManager.PERMISSION_GRANTED;
+    }
+
+}