commit 1bdf075964245f86f35d8a78bb12c8226de8806d
author Junyu Lai <junyulai@google.com> Wed Jul 14 06:44:37 2021 +0000
committer Junyu Lai <junyulai@google.com> Mon Jul 26 09:16:35 2021 +0000
tree d4d659c27090daecd28b27642f683c9c5e8c60f8
parent b07a5e14137ebbeb909f926357ff32c95baab338

Fix mMobileIfaces is not protected by lock

Currently, mMobileIfaces is accessed from multiple threads, and
should be protected from concurrent accessing. However, since the
variable could be accessed frequently, holding the mStatsLock
would make this be blocked by network stats I/O operations.
Thus, protect the variable by making it volatile.

Test: Wifi on/off stress test
Bug: 192758557
Change-Id: Ie7694a63f5203ee7c83830ca13d97219b7949fd7

services/core/java/com/android/server/net/NetworkStatsService.java

diff --git a/services/core/java/com/android/server/net/NetworkStatsService.java b/services/core/java/com/android/server/net/NetworkStatsService.java
index 4ee867b..f571b35 100644
--- a/services/core/java/com/android/server/net/NetworkStatsService.java
+++ b/services/core/java/com/android/server/net/NetworkStatsService.java
@@ -289,8 +289,7 @@
     private String mActiveIface;
 
     /** Set of any ifaces associated with mobile networks since boot. */
-    @GuardedBy("mStatsLock")
-    private String[] mMobileIfaces = new String[0];
+    private volatile String[] mMobileIfaces = new String[0];
 
     /** Set of all ifaces currently used by traffic that does not explicitly specify a Network. */
     @GuardedBy("mStatsLock")
@@ -935,7 +934,7 @@
 
     @Override
     public String[] getMobileIfaces() {
-        return mMobileIfaces;
+        return mMobileIfaces.clone();
     }
 
     @Override
@@ -1084,7 +1083,8 @@
     }
 
     @Override
-    public long getIfaceStats(String iface, int type) {
+    public long getIfaceStats(@NonNull String iface, int type) {
+        Objects.requireNonNull(iface);
         long nativeIfaceStats = nativeGetIfaceStat(iface, type, checkBpfStatsEnable());
         if (nativeIfaceStats == -1) {
             return nativeIfaceStats;
@@ -1382,7 +1382,7 @@
             }
         }
 
-        mMobileIfaces = mobileIfaces.toArray(new String[mobileIfaces.size()]);
+        mMobileIfaces = mobileIfaces.toArray(new String[0]);
     }
 
     private static int getSubIdForMobile(@NonNull NetworkStateSnapshot state) {