StrictMode: check max-offenses-per-loop earlier, before allocations

Previously a tight loop of StrictMode violations would still allocate
Exception objects and populate their stack frames, just to orphan them
later when checking the max-10-violations-per-loop constraint.

With this patch, we do that check _before_ allocating any memory.

Change-Id: Iae96aba33f8fcc6a8ec5838a231aecc08e95122d

1 files changed, 25 insertions, 8 deletions

diff --git a/core/java/android/os/StrictMode.java b/core/java/android/os/StrictMode.java
index 9494a06..c185007 100644
--- a/core/java/android/os/StrictMode.java
+++ b/core/java/android/os/StrictMode.java
@@ -104,6 +104,10 @@ public final class StrictMode {
     // Only show an annoying dialog at most every 30 seconds
     private static final long MIN_DIALOG_INTERVAL_MS = 30000;
 
+    // How many offending stacks to keep track of (and time) per loop
+    // of the Looper.
+    private static final int MAX_OFFENSES_PER_LOOP = 10;
+
     // Thread-policy:
 
     /**
@@ -680,6 +684,17 @@ public final class StrictMode {
         }
     }
 
+    private static final ThreadLocal<ArrayList<ViolationInfo>> violationsBeingTimed =
+            new ThreadLocal<ArrayList<ViolationInfo>>() {
+        @Override protected ArrayList<ViolationInfo> initialValue() {
+            return new ArrayList<ViolationInfo>();
+        }
+    };
+
+    private static boolean tooManyViolationsThisLoop() {
+        return violationsBeingTimed.get().size() >= MAX_OFFENSES_PER_LOOP;
+    }
+
     private static class AndroidBlockGuardPolicy implements BlockGuard.Policy {
         private int mPolicyMask;
 
@@ -707,6 +722,9 @@ public final class StrictMode {
             if ((mPolicyMask & DETECT_DISK_WRITE) == 0) {
                 return;
             }
+            if (tooManyViolationsThisLoop()) {
+                return;
+            }
             BlockGuard.BlockGuardPolicyException e = new StrictModeDiskWriteViolation(mPolicyMask);
             e.fillInStackTrace();
             startHandlingViolationException(e);
@@ -717,6 +735,9 @@ public final class StrictMode {
             if ((mPolicyMask & DETECT_DISK_READ) == 0) {
                 return;
             }
+            if (tooManyViolationsThisLoop()) {
+                return;
+            }
             BlockGuard.BlockGuardPolicyException e = new StrictModeDiskReadViolation(mPolicyMask);
             e.fillInStackTrace();
             startHandlingViolationException(e);
@@ -727,6 +748,9 @@ public final class StrictMode {
             if ((mPolicyMask & DETECT_NETWORK) == 0) {
                 return;
             }
+            if (tooManyViolationsThisLoop()) {
+                return;
+            }
             BlockGuard.BlockGuardPolicyException e = new StrictModeNetworkViolation(mPolicyMask);
             e.fillInStackTrace();
             startHandlingViolationException(e);
@@ -747,13 +771,6 @@ public final class StrictMode {
             handleViolationWithTimingAttempt(info);
         }
 
-        private static final ThreadLocal<ArrayList<ViolationInfo>> violationsBeingTimed =
-                new ThreadLocal<ArrayList<ViolationInfo>>() {
-            @Override protected ArrayList<ViolationInfo> initialValue() {
-                return new ArrayList<ViolationInfo>();
-            }
-        };
-
         // Attempts to fill in the provided ViolationInfo's
         // durationMillis field if this thread has a Looper we can use
         // to measure with.  We measure from the time of violation
@@ -780,7 +797,7 @@ public final class StrictMode {
 
             MessageQueue queue = Looper.myQueue();
             final ArrayList<ViolationInfo> records = violationsBeingTimed.get();
-            if (records.size() >= 10) {
+            if (records.size() >= MAX_OFFENSES_PER_LOOP) {
                 // Not worth measuring.  Too many offenses in one loop.
                 return;
             }