Jorim Jaggi | 36db127 | 2017-03-28 00:43:31 +0200 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright (C) 2017 The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License |
| 15 | */ |
| 16 | |
| 17 | package com.android.server; |
| 18 | |
| 19 | import android.os.Process; |
| 20 | |
| 21 | /** |
| 22 | * Utility class to boost threads in sections where important locks are held. |
| 23 | */ |
| 24 | public class ThreadPriorityBooster { |
| 25 | |
| 26 | private final int mBoostToPriority; |
| 27 | private final int mLockGuardIndex; |
| 28 | |
| 29 | private final ThreadLocal<PriorityState> mThreadState = new ThreadLocal<PriorityState>() { |
| 30 | @Override protected PriorityState initialValue() { |
| 31 | return new PriorityState(); |
| 32 | } |
| 33 | }; |
| 34 | |
| 35 | public ThreadPriorityBooster(int boostToPriority, int lockGuardIndex) { |
| 36 | mBoostToPriority = boostToPriority; |
| 37 | mLockGuardIndex = lockGuardIndex; |
| 38 | } |
| 39 | |
| 40 | public void boost() { |
| 41 | final int tid = Process.myTid(); |
| 42 | final int prevPriority = Process.getThreadPriority(tid); |
| 43 | PriorityState state = mThreadState.get(); |
| 44 | if (state.regionCounter == 0 && prevPriority > mBoostToPriority) { |
| 45 | state.prevPriority = prevPriority; |
| 46 | Process.setThreadPriority(tid, mBoostToPriority); |
| 47 | } |
| 48 | state.regionCounter++; |
| 49 | if (LockGuard.ENABLED) { |
| 50 | LockGuard.guard(mLockGuardIndex); |
| 51 | } |
| 52 | } |
| 53 | |
| 54 | public void reset() { |
| 55 | PriorityState state = mThreadState.get(); |
| 56 | state.regionCounter--; |
| 57 | if (state.regionCounter == 0 && state.prevPriority > mBoostToPriority) { |
| 58 | Process.setThreadPriority(Process.myTid(), state.prevPriority); |
| 59 | } |
| 60 | } |
| 61 | |
| 62 | private static class PriorityState { |
| 63 | |
| 64 | /** |
| 65 | * Acts as counter for number of synchronized region that needs to acquire 'this' as a lock |
| 66 | * the current thread is currently in. When it drops down to zero, we will no longer boost |
| 67 | * the thread's priority. |
| 68 | */ |
| 69 | int regionCounter; |
| 70 | |
| 71 | /** |
| 72 | * The thread's previous priority before boosting. |
| 73 | */ |
| 74 | int prevPriority; |
| 75 | } |
| 76 | } |