Commit 282cf6ea authored Mar 05, 2019 by Riddle Hsu

Fix missing incremental process starting position of LRU list

When searching insertion position for a process with clients activities,
if the position goes to mLruProcessActivityStart but we don't increase
mLruProcessActivityStart, it will be like hide a slot. Then when removing
the process from LRU, the starting position will be decreased, that causes
a slot is lost. After this condition happens many times, the starting
position (mLruProcessServiceStart in the practical case) becomes a negative
number which leads to IndexOutOfBoundsException.

The expected example:
 Assume to insert a new process X to [2]:
  [0]A
  [1]B
  [2]C <- mLruProcess(Activity/Service)Start
  [3]D
 After insertion, the starting position increased:
  [0]A
  [1]B
  [2]X
  [3]C <- mLruProcess(Activity/Service)Start
  [4]D

Bug: 126427214
Test: Build system/extras/tests/memeater and push to device.
      Execute multiple memeater instances to consume most of RAM.
      Observe home is being killed and restarted frequently for a
      long time without IndexOutOfBoundsException from LRU list.

Change-Id: I8a925aa320141e55e18fa4312ba91cb628bcc47d

parent 5af401bd

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

+9 −0

Original line number	Diff line number	Diff line
		@@ -2852,6 +2852,15 @@ public final class ProcessList {
		pos--;
		}
		mLruProcesses.add(pos, app);
		if (pos == mLruProcessActivityStart) {
		mLruProcessActivityStart++;
		}
		if (pos == mLruProcessServiceStart) {
		// Unless {@code #hasService} is implemented, currently the starting position
		// for activity and service are the same, so the incoming position may equal to
		// the starting position of service.
		mLruProcessServiceStart++;
		}
		// If this process is part of a group, need to pull up any other processes
		// in that group to be with it.
		int endIndex = pos - 1;