Collect native TIDs for binder threads

This information will be used for attribution of CPU
usage to work source UIDs.

Bug: 158232997
Test: atest FrameworksCoreTests:com.android.internal.os.BinderCallsStatsTest

Change-Id: Ic9fcc1d62515dd11a1fbade80264412615014919

core/java/android/os/Binder.java

@@ -122,6 +122,13 @@ public class Binder implements IBinder {
 
     private static native long getNativeFinalizer();
 
+    /**
+     * Returns the TID (task ID) for the current thread. Same as {@link Thread#getNativeTid()}
+     *
+     * @hide
+     */
+    public static native int getNativeTid();
+
     // Use a Holder to allow static initialization of Binder in the boot image, and
     // possibly to avoid some initialization ordering issues.
     private static class NoImagePreloadHolder {

core/java/com/android/internal/os/BinderCallsStats.java

@@ -27,6 +27,7 @@ import android.os.UserHandle;
 import android.text.format.DateFormat;
 import android.util.ArrayMap;
 import android.util.ArraySet;
+import android.util.IntArray;
 import android.util.Pair;
 import android.util.Slog;
 import android.util.SparseArray;
@@ -126,6 +127,11 @@ public class BinderCallsStats implements BinderInternal.Observer {
         }
     };
 
+    private final Object mNativeTidsLock = new Object();
+    // @GuardedBy("mNativeTidsLock")  // Cannot mark it as "GuardedBy" because it's read
+    // directly, as a volatile field.
+    private volatile IntArray mNativeTids = new IntArray(0);
+
     /** Injector for {@link BinderCallsStats}. */
     public static class Injector {
         public Random getRandomGenerator() {
@@ -175,6 +181,8 @@ public class BinderCallsStats implements BinderInternal.Observer {
             return null;
         }
 
+        noteNativeThreadId();
+
         final CallSession s = obtainCallSession();
         s.binderClass = binder.getClass();
         s.transactionCode = code;
@@ -312,6 +320,27 @@ public class BinderCallsStats implements BinderInternal.Observer {
         }
     }
 
+    private void noteNativeThreadId() {
+        final int tid = getNativeTid();
+        int index = mNativeTids.binarySearch(tid);
+        if (index >= 0) {
+            return;
+        }
+
+        // Use the copy-on-write approach. The changes occur exceedingly infrequently, so
+        // this code path is exercised just a few times per boot
+        synchronized (mNativeTidsLock) {
+            IntArray nativeTids = mNativeTids;
+            index = nativeTids.binarySearch(tid);
+            if (index < 0) {
+                IntArray copyOnWriteArray = new IntArray(nativeTids.size() + 1);
+                copyOnWriteArray.addAll(nativeTids);
+                copyOnWriteArray.add(-index - 1, tid);
+                mNativeTids = copyOnWriteArray;
+            }
+        }
+    }
+
     /**
      * This method is expensive to call.
      */
@@ -505,6 +534,17 @@ public class BinderCallsStats implements BinderInternal.Observer {
         return Binder.getCallingUid();
     }
 
+    protected int getNativeTid() {
+        return Binder.getNativeTid();
+    }
+
+    /**
+     * Returns known Linux TIDs for threads taking incoming binder calls.
+     */
+    public int[] getNativeTids() {
+        return mNativeTids.toArray();
+    }
+
     protected long getElapsedRealtimeMicro() {
         return SystemClock.elapsedRealtimeNanos() / 1000;
     }

core/jni/android_util_Binder.cpp

@@ -30,6 +30,7 @@
 #include <unistd.h>
 
 #include <android-base/stringprintf.h>
+#include <android-base/threads.h>
 #include <binder/BpBinder.h>
 #include <binder/IInterface.h>
 #include <binder/IPCThreadState.h>
@@ -1047,6 +1048,10 @@ static void android_os_Binder_setExtension(JNIEnv* env, jobject obj, jobject ext
     jbh->setExtension(extension);
 }
 
+JNIEXPORT jint JNICALL android_os_Binder_getNativeTid(JNIEnv* env, jobject clazz) {
+    return (jint)android::base::GetThreadId();
+}
+
 // ----------------------------------------------------------------------------
 
 static const JNINativeMethod gBinderMethods[] = {
@@ -1078,6 +1083,7 @@ static const JNINativeMethod gBinderMethods[] = {
     { "blockUntilThreadAvailable", "()V", (void*)android_os_Binder_blockUntilThreadAvailable },
     { "getExtension", "()Landroid/os/IBinder;", (void*)android_os_Binder_getExtension },
     { "setExtension", "(Landroid/os/IBinder;)V", (void*)android_os_Binder_setExtension },
+    { "getNativeTid", "()I", (void*)android_os_Binder_getNativeTid },
 };
 
 const char* const kBinderPathName = "android/os/Binder";

core/tests/coretests/src/com/android/internal/os/BinderCallsStatsTest.java

@@ -807,6 +807,38 @@ public class BinderCallsStatsTest {
         }
     }
 
+    @Test
+    public void testNativeTids() {
+        TestBinderCallsStats bcs = new TestBinderCallsStats();
+        Binder binder = new Binder();
+
+        bcs.nativeTid = 3;
+
+        CallSession callSession = bcs.callStarted(binder, 1, WORKSOURCE_UID);
+        bcs.callEnded(callSession, REQUEST_SIZE, REPLY_SIZE, WORKSOURCE_UID);
+
+        bcs.nativeTid = 1;
+
+        callSession = bcs.callStarted(binder, 1, WORKSOURCE_UID);
+        bcs.callEnded(callSession, REQUEST_SIZE, REPLY_SIZE, WORKSOURCE_UID);
+
+        bcs.nativeTid = 1;
+
+        callSession = bcs.callStarted(binder, 1, WORKSOURCE_UID);
+        bcs.callEnded(callSession, REQUEST_SIZE, REPLY_SIZE, WORKSOURCE_UID);
+
+        bcs.nativeTid = 2;
+
+        callSession = bcs.callStarted(binder, 1, WORKSOURCE_UID);
+        bcs.callEnded(callSession, REQUEST_SIZE, REPLY_SIZE, WORKSOURCE_UID);
+
+        int[] tids = bcs.getNativeTids();
+        assertEquals(3, tids.length);
+        assertEquals(1, tids[0]);
+        assertEquals(2, tids[1]);
+        assertEquals(3, tids[2]);
+    }
+
     private static class TestHandler extends Handler {
         ArrayList<Runnable> mRunnables = new ArrayList<>();
 
@@ -825,6 +857,7 @@ public class BinderCallsStatsTest {
         public int callingUid = CALLING_UID;
         public long time = 1234;
         public long elapsedTime = 0;
+        public int nativeTid;
 
         TestBinderCallsStats() {
             this(mDeviceState);
@@ -874,6 +907,10 @@ public class BinderCallsStatsTest {
         protected void setCallingUid(int uid) {
             callingUid = uid;
         }
-    }
 
+        @Override
+        protected int getNativeTid() {
+            return nativeTid;
+        }
+    }
 }