1 files changed, 64 insertions, 0 deletions
diff --git a/services/core/java/com/android/server/os/SchedulingPolicyService.java b/services/core/java/com/android/server/os/SchedulingPolicyService.java
new file mode 100644
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--- /dev/null
+++ b/services/core/java/com/android/server/os/SchedulingPolicyService.java
@@ -0,0 +1,64 @@
+/*
+ * 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 com.android.server.os;
+
+import android.content.pm.PackageManager;
+import android.os.Binder;
+import android.os.ISchedulingPolicyService;
+import android.os.Process;
+
+/**
+ * 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 = 3;
+
+    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;
+    }
+
+}