tree cb151c40090d3ef12efe6b5c5f7ed6e0d6911bf4
parent 1b2ed4394c0e10c844faa4840067db4ee4a2367c
author Hugo Benichi <hugobenichi@google.com> 1466470087 +0900
committer Hugo Benichi <hugobenichi@google.com> 1467007467 +0900

Fix unsafe concurrent access in LegacyTypeTracker

This patch adds synchronization inside LegacyTypeTracker so that
getNetworkForType() can safely run concurrently with remove().

Without synchronization if remove() removes the last network for a
given type while getNetworkForType() runs for the same type, it is
possible that getNetworkForType tries to access the head of an empty
list, resulting in a runtime exception.

This issue was found by zoran.jovanovic@sonymobile.com who proposed a
fix in AOSP (Change-Id: Ia963662edb9d643790e8d9439e4dbdcac4c2187b).

This patch differs from the fix proposed by the bug reporter and tries
instead to do the minimum amount of locking to make getNetworkForType
safe.

Bug: 29030387
Change-Id: I915aac527fc8828b32bf35fee870add2dfb11d8d