Merge "Do not cache enabled tags in Java." (e280c890) · Commits · e / os / android_frameworks_base

core/java/android/os/Trace.java

+5 −49

Original line number	Diff line number	Diff line
		@@ -21,6 +21,7 @@ import android.annotation.UnsupportedAppUsage;

		import com.android.internal.os.Zygote;

		import dalvik.annotation.optimization.CriticalNative;
		import dalvik.annotation.optimization.FastNative;

		/**
		@@ -107,12 +108,15 @@ public final class Trace {
		private static final int MAX_SECTION_NAME_LEN = 127;

		// Must be volatile to avoid word tearing.
		// This is only kept in case any apps get this by reflection but do not
		// check the return value for null.
		@UnsupportedAppUsage
		private static volatile long sEnabledTags = TRACE_TAG_NOT_READY;

		private static int sZygoteDebugFlags = 0;

		@UnsupportedAppUsage
		@CriticalNative
		private static native long nativeGetEnabledTags();
		private static native void nativeSetAppTracingAllowed(boolean allowed);
		private static native void nativeSetTracingEnabled(boolean allowed);
		@@ -128,46 +132,9 @@ public final class Trace {
		@FastNative
		private static native void nativeAsyncTraceEnd(long tag, String name, int cookie);

		static {
		// We configure two separate change callbacks, one in Trace.cpp and one here. The
		// native callback reads the tags from the system property, and this callback
		// reads the value that the native code retrieved. It's essential that the native
		// callback executes first.
		//
		// The system provides ordering through a priority level. Callbacks made through
		// SystemProperties.addChangeCallback currently have a negative priority, while
		// our native code is using a priority of zero.
		SystemProperties.addChangeCallback(() -> {
		cacheEnabledTags();
		if ((sZygoteDebugFlags & Zygote.DEBUG_JAVA_DEBUGGABLE) != 0) {
		traceCounter(TRACE_TAG_ALWAYS, "java_debuggable", 1);
		}
		});
		}

		private Trace() {
		}

		/**
		* Caches a copy of the enabled-tag bits. The "master" copy is held by the native code,
		* and comes from the PROPERTY_TRACE_TAG_ENABLEFLAGS property.
		* <p>
		* If the native code hasn't yet read the property, we will cause it to do one-time
		* initialization. We don't want to do this during class init, because this class is
		* preloaded, so all apps would be stuck with whatever the zygote saw. (The zygote
		* doesn't see the system-property update broadcasts.)
		* <p>
		* We want to defer initialization until the first use by an app, post-zygote.
		* <p>
		* We're okay if multiple threads call here simultaneously -- the native state is
		* synchronized, and sEnabledTags is volatile (prevents word tearing).
		*/
		private static long cacheEnabledTags() {
		long tags = nativeGetEnabledTags();
		sEnabledTags = tags;
		return tags;
		}

		/**
		* Returns true if a trace tag is enabled.
		*
		@@ -178,10 +145,7 @@ public final class Trace {
		*/
		@UnsupportedAppUsage
		public static boolean isTagEnabled(long traceTag) {
		long tags = sEnabledTags;
		if (tags == TRACE_TAG_NOT_READY) {
		tags = cacheEnabledTags();
		}
		long tags = nativeGetEnabledTags();
		return (tags & traceTag) != 0;
		}

		@@ -210,10 +174,6 @@ public final class Trace {
		@UnsupportedAppUsage
		public static void setAppTracingAllowed(boolean allowed) {
		nativeSetAppTracingAllowed(allowed);

		// Setting whether app tracing is allowed may change the tags, so we update the cached
		// tags here.
		cacheEnabledTags();
		}

		/**
		@@ -227,10 +187,6 @@ public final class Trace {
		public static void setTracingEnabled(boolean enabled, int debugFlags) {
		nativeSetTracingEnabled(enabled);
		sZygoteDebugFlags = debugFlags;

		// Setting whether tracing is enabled may change the tags, so we update the cached tags
		// here.
		cacheEnabledTags();
		}

		/**

core/jni/android_os_Trace.cpp

+5 −7

Original line number	Diff line number	Diff line
		@@ -50,10 +50,6 @@ inline static void withString(JNIEnv* env, jstring jstr, F callback) {
		callback(buffer.data());
		}

		static jlong android_os_Trace_nativeGetEnabledTags(JNIEnv*, jclass) {
		return atrace_get_enabled_tags();
		}

		static void android_os_Trace_nativeTraceCounter(JNIEnv* env, jclass,
		jlong tag, jstring nameStr, jlong value) {
		withString(env, nameStr, [tag, value](char* str) {
		@@ -96,9 +92,6 @@ static void android_os_Trace_nativeSetTracingEnabled(JNIEnv*, jclass, jboolean e

		static const JNINativeMethod gTraceMethods[] = {
		/* name, signature, funcPtr */
		{ "nativeGetEnabledTags",
		"()J",
		(void*)android_os_Trace_nativeGetEnabledTags },
		{ "nativeSetAppTracingAllowed",
		"(Z)V",
		(void*)android_os_Trace_nativeSetAppTracingAllowed },
		@@ -123,6 +116,11 @@ static const JNINativeMethod gTraceMethods[] = {
		{ "nativeAsyncTraceEnd",
		"(JLjava/lang/String;I)V",
		(void*)android_os_Trace_nativeAsyncTraceEnd },

		// ----------- @CriticalNative ----------------
		{ "nativeGetEnabledTags",
		"()J",
		(void*)atrace_get_enabled_tags },
		};

		int register_android_os_Trace(JNIEnv* env) {