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Commit 80a05232 authored by Marco Ballesio's avatar Marco Ballesio
Browse files

ActivityManager: don't freeze processes holding file locks 

As a temporary measure waiting for the more robust b/176927978 to be
implemented, query the file lock status of processes prior freezing
them, and skip freeze if any locks are held.

Test: verified form the logs that processes holding file locks are not
frozen
Bug: 176928302

Change-Id: Ib7e1715effb63c1b304ce22a9451294fd9f7b10d
Merged-In: Ib7e1715effb63c1b304ce22a9451294fd9f7b10d
parent 2dd4e12e

core/java/android/os/Process.java

+38 −0
Original line number Diff line number Diff line
@@ -31,8 +31,12 @@ import dalvik.system.VMRuntime; 


import libcore.io.IoUtils;



import java.io.BufferedReader;

import java.io.FileDescriptor;

import java.io.FileReader;

import java.io.IOException;

import java.util.Map;

import java.util.StringTokenizer;

import java.util.concurrent.TimeoutException;



/**
@@ -1393,4 +1397,38 @@ public class Process { 
    }



    private static native int nativePidFdOpen(int pid, int flags) throws ErrnoException;



    /**

     * Checks if a process corresponding to a specific pid owns any file locks.

     * @param pid The process ID for which we want to know the existence of file locks.

     * @return true If the process holds any file locks, false otherwise.

     * @throws IOException if /proc/locks can't be accessed.

     *

     * @hide

     */

    public static boolean hasFileLocks(int pid) throws IOException {

        BufferedReader br = null;



        try {

            br = new BufferedReader(new FileReader("/proc/locks"));

            String line;



            while ((line = br.readLine()) != null) {

                StringTokenizer st = new StringTokenizer(line);



                for (int i = 0; i < 5 && st.hasMoreTokens(); i++) {

                    String str = st.nextToken();

                    if (i == 4 && Integer.parseInt(str) == pid) {

                        return true;

                    }

                }

            }



            return false;

        } finally {

            if (br != null) {

                br.close();

            }

        }

    }

}

services/core/java/com/android/server/am/CachedAppOptimizer.java

+57 −25
Original line number Diff line number Diff line
@@ -1101,15 +1101,26 @@ public final class CachedAppOptimizer { 
        }



        private void freezeProcess(ProcessRecord proc) {

            final int pid;

            final String name;

            final int pid = proc.pid;

            final String name = proc.processName;

            final long unfrozenDuration;

            final boolean frozen;



            synchronized (mAm) {

                pid = proc.pid;

                name = proc.processName;

            try {

                // pre-check for locks to avoid unnecessary freeze/unfreeze operations

                if (Process.hasFileLocks(pid)) {

                    if (DEBUG_FREEZER) {

                        Slog.d(TAG_AM, name + " (" + pid + ") holds file locks, not freezing");

                    }

                    return;

                }

            } catch (IOException e) {

                Slog.e(TAG_AM, "Not freezing. Unable to check file locks for " + name + "(" + pid

                        + "): " + e);

                return;

            }



            synchronized (mAm) {

                if (proc.curAdj < ProcessList.CACHED_APP_MIN_ADJ

                        || proc.shouldNotFreeze) {

                    if (DEBUG_FREEZER) {
@@ -1141,7 +1152,11 @@ public final class CachedAppOptimizer { 
                frozen = proc.frozen;

            }



            if (frozen) {

            if (!frozen) {

                return;

            }





            if (DEBUG_FREEZER) {

                Slog.d(TAG_AM, "froze " + pid + " " + name);

            }
@@ -1165,6 +1180,23 @@ public final class CachedAppOptimizer { 
                        name,

                        unfrozenDuration);

            }



            try {

                // post-check to prevent races

                if (Process.hasFileLocks(pid)) {

                    if (DEBUG_FREEZER) {

                        Slog.d(TAG_AM, name + " (" + pid + ") holds file locks, reverting freeze");

                    }



                    synchronized (mAm) {

                        unfreezeAppLocked(proc);

                    }

                }

            } catch (IOException e) {

                Slog.e(TAG_AM, "Unable to check file locks for " + name + "(" + pid + "): " + e);

                synchronized (mAm) {

                    unfreezeAppLocked(proc);

                }

            }

        }