From 37ae22f321320ce43452667652b56e8a032948f0 Mon Sep 17 00:00:00 2001
From: Marco Ballesio <balejs@google.com>
Date: Mon, 1 Jun 2020 11:12:54 -0700
Subject: [PATCH] freezer: switch to cgroup v2 freezer

cgroup v2 freezer has a single hierarchy and is mounted under
/sys/fs/cgroup. Proper v2 freezer support in a system can be checked by
verifying that the file "cgroup.freeze" is present in a freezer subgroup.

Bug: 154548692
Test: manually verified that processes are frozen and unfrozen

Change-Id: Ib966a957490ec986eb14aba6492832c96e147896
---
 core/java/android/os/Process.java              |  2 +-
 core/jni/android_util_Process.cpp              |  4 ++--
 .../android/server/am/CachedAppOptimizer.java  | 18 +++++++++++-------
 3 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/core/java/android/os/Process.java b/core/java/android/os/Process.java
index a4077fbee892e..efea9537c4cfe 100644
--- a/core/java/android/os/Process.java
+++ b/core/java/android/os/Process.java
@@ -947,7 +947,7 @@ public class Process {
 
     /**
      * Enable or disable the freezer. When enable == false all frozen processes are unfrozen,
-     * but aren't removed from the freezer. Processes can still be added or removed
+     * but aren't removed from the freezer. While in this state, processes can be added or removed
      * by using setProcessFrozen, but they won't actually be frozen until the freezer is enabled
      * again. If enable == true the freezer is enabled again, and all processes
      * in the freezer (including the ones added while the freezer was disabled) are frozen.
diff --git a/core/jni/android_util_Process.cpp b/core/jni/android_util_Process.cpp
index cbcbe7f113903..7036e9a6d5b0c 100644
--- a/core/jni/android_util_Process.cpp
+++ b/core/jni/android_util_Process.cpp
@@ -378,9 +378,9 @@ void android_os_Process_enableFreezer(
     bool success = true;
 
     if (enable) {
-        success = SetTaskProfiles(0, {"FreezerFrozen"}, true);
+        success = SetTaskProfiles(0, {"FreezerEnabled"}, true);
     } else {
-        success = SetTaskProfiles(0, {"FreezerThawed"}, true);
+        success = SetTaskProfiles(0, {"FreezerDisabled"}, true);
     }
 
     if (!success) {
diff --git a/services/core/java/com/android/server/am/CachedAppOptimizer.java b/services/core/java/com/android/server/am/CachedAppOptimizer.java
index d9fde0f6728a8..ce7c73a5d8a31 100644
--- a/services/core/java/com/android/server/am/CachedAppOptimizer.java
+++ b/services/core/java/com/android/server/am/CachedAppOptimizer.java
@@ -420,25 +420,25 @@ public final class CachedAppOptimizer {
     }
 
     /**
-     * Determines whether the freezer is correctly supported by this system
+     * Determines whether the freezer is supported by this system
      */
     public static boolean isFreezerSupported() {
         boolean supported = false;
         FileReader fr = null;
 
         try {
-            fr = new FileReader("/dev/freezer/frozen/freezer.killable");
-            int i = fr.read();
+            fr = new FileReader("/sys/fs/cgroup/freezer/cgroup.freeze");
+            char state = (char) fr.read();
 
-            if ((char) i == '1') {
+            if (state == '1' || state == '0') {
                 supported = true;
             } else {
-                Slog.w(TAG_AM, "Freezer killability is turned off, disabling freezer");
+                Slog.e(TAG_AM, "unexpected value in cgroup.freeze");
             }
         } catch (java.io.FileNotFoundException e) {
-            Slog.d(TAG_AM, "Freezer.killable not present, disabling freezer");
+            Slog.d(TAG_AM, "cgroup.freeze not present");
         } catch (Exception e) {
-            Slog.d(TAG_AM, "Unable to read freezer.killable, disabling freezer: " + e.toString());
+            Slog.d(TAG_AM, "unable to read cgroup.freeze: " + e.toString());
         }
 
         if (fr != null) {
@@ -471,6 +471,8 @@ public final class CachedAppOptimizer {
 
         if (mUseFreezer && mFreezeHandler == null) {
             Slog.d(TAG_AM, "Freezer enabled");
+            Process.enableFreezer(true);
+
             if (!mCachedAppOptimizerThread.isAlive()) {
                 mCachedAppOptimizerThread.start();
             }
@@ -479,6 +481,8 @@ public final class CachedAppOptimizer {
 
             Process.setThreadGroupAndCpuset(mCachedAppOptimizerThread.getThreadId(),
                     Process.THREAD_GROUP_SYSTEM);
+        } else {
+            Process.enableFreezer(false);
         }
     }