From bc7b6df7dc363404df21b062a016aa19923b24de Mon Sep 17 00:00:00 2001
From: Jing Ji <jji@google.com>
Date: Thu, 28 Jan 2021 00:42:19 -0800
Subject: [PATCH] Adapt the cgroup v2 in PhantomProcessList

Bug: 178675122
Test: atest AppChildProcessTest
Test: atest CtsAppTestCases:ActivityManagerTest
Change-Id: Ifad53ae06bc77da97ffae580d0078a006b4159b7
---
 .../android/server/am/PhantomProcessList.java | 27 +++++++++++++++++--
 .../server/am/AppChildProcessTest.java        |  2 +-
 2 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/services/core/java/com/android/server/am/PhantomProcessList.java b/services/core/java/com/android/server/am/PhantomProcessList.java
index 5167c57199551..37b17411dac58 100644
--- a/services/core/java/com/android/server/am/PhantomProcessList.java
+++ b/services/core/java/com/android/server/am/PhantomProcessList.java
@@ -38,6 +38,7 @@ import com.android.internal.os.ProcessCpuTracker;
 
 import libcore.io.IoUtils;
 
+import java.io.File;
 import java.io.FileDescriptor;
 import java.io.FileInputStream;
 import java.io.FileNotFoundException;
@@ -109,10 +110,23 @@ public final class PhantomProcessList {
     private final ActivityManagerService mService;
     private final Handler mKillHandler;
 
+    private static final int CGROUP_V1 = 0;
+    private static final int CGROUP_V2 = 1;
+    private static final String[] CGROUP_PATH_PREFIXES = {
+        "/acct/uid_" /* cgroup v1 */,
+        "/sys/fs/cgroup/uid_" /* cgroup v2 */
+    };
+    private static final String CGROUP_PID_PREFIX = "/pid_";
+    private static final String CGROUP_PROCS = "/cgroup.procs";
+
+    @VisibleForTesting
+    int mCgroupVersion = CGROUP_V1;
+
     PhantomProcessList(final ActivityManagerService service) {
         mService = service;
         mKillHandler = service.mProcessList.sKillHandler;
         mInjector = new Injector();
+        probeCgroupVersion();
     }
 
     @VisibleForTesting
@@ -190,9 +204,18 @@ public final class PhantomProcessList {
         }
     }
 
+    private void probeCgroupVersion() {
+        for (int i = CGROUP_PATH_PREFIXES.length - 1; i >= 0; i--) {
+            if ((new File(CGROUP_PATH_PREFIXES[i] + Process.SYSTEM_UID)).exists()) {
+                mCgroupVersion = i;
+                break;
+            }
+        }
+    }
+
     @VisibleForTesting
-    static String getCgroupFilePath(int uid, int pid) {
-        return "/acct/uid_" + uid + "/pid_" + pid + "/cgroup.procs";
+    String getCgroupFilePath(int uid, int pid) {
+        return CGROUP_PATH_PREFIXES[mCgroupVersion] + uid + CGROUP_PID_PREFIX + pid + CGROUP_PROCS;
     }
 
     static String getProcessName(int pid) {
diff --git a/services/tests/mockingservicestests/src/com/android/server/am/AppChildProcessTest.java b/services/tests/mockingservicestests/src/com/android/server/am/AppChildProcessTest.java
index b85da94604760..17f326fbdbce4 100644
--- a/services/tests/mockingservicestests/src/com/android/server/am/AppChildProcessTest.java
+++ b/services/tests/mockingservicestests/src/com/android/server/am/AppChildProcessTest.java
@@ -298,7 +298,7 @@ public class AppChildProcessTest {
         }
 
         void addToProcess(int uid, int pid, int newPid) {
-            final String path = PhantomProcessList.getCgroupFilePath(uid, pid);
+            final String path = mPhantomProcessList.getCgroupFilePath(uid, pid);
             StringBuffer sb = mPathToData.get(path);
             if (sb == null) {
                 sb = new StringBuffer();