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Commit 176736ca authored by Mohamad Mahmoud's avatar Mohamad Mahmoud
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Introduce LongMethodTracer: signal-based method tracing utility 

Adds a new utility (LongMethodTracer) to trigger method tracing in native processes via signal, as part of the pre-ANR tracing mechanism.

- Adds LongMethodTracer class in Java, providing APIs to trigger tracing for one or multiple processes.
- Implements JNI bindings for LongMethodTracer, handling signal delivery using sigqueue with packed payloads.
- Introduces a type-tagging convention in sigval to differentiate tracing requests (LONG_METHOD_TRACING_TYPE_ID).

This utility abstracts the signal-based tracing trigger, enabling lightweight integration for pre-ANR diagnostics.

Test: ran multiple scenarios and  verified signal delivery and tracing manually
Bug: 413119509
Flag: com.android.server.utils.long_method_trace
Design Document: go/long-method-tracing-for-anrs

Change-Id: I545e2724cec3db5bed1fc884700ac2338e1ccec9
parent 6f1f1631

services/core/java/com/android/server/utils/LongMethodTracer.java

0 → 100644
+74 −0
Original line number Diff line number Diff line 
/*

 * Copyright (C) 2025 The Android Open Source Project

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 *

 *      http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */



package com.android.server.utils;



import static android.os.Trace.TRACE_TAG_ACTIVITY_MANAGER;



import android.os.Trace;

import android.util.Slog;



import com.android.internal.annotations.Keep;



/**

 * Triggers long method tracing in a process for a fixed duration.

 *

 * <p>This uses a native signal-based mechanism to request tracing in the target process. The actual

 * signal and delivery mechanism are abstracted away.

 *

 * <p>The collected tracing information currently appears in the ANR report if the traced process

 * encounters an ANR during or after the tracing window.

 *

 * @hide

 */

public class LongMethodTracer {

    private static final String TAG = "LongMethodTracer";



    /**

     * Requests method tracing in the given process.

     *

     * @param pid The target process ID to trace.

     * @param durationMs The tracing duration in milliseconds.

     * @return true if the request was successfully sent; false otherwise.

     */

    @Keep

    public static boolean trigger(int pid, int durationMs) {

        if (!Flags.longMethodTrace()) {

            return false;

        }



        if (pid <= 0) {

            throw new IllegalArgumentException("Invalid PID: " + pid);

        }

        if (durationMs <= 0) {

            throw new IllegalArgumentException("Duration must be positive: " + durationMs);

        }



        Trace.traceBegin(TRACE_TAG_ACTIVITY_MANAGER,

                "LongMethodTracer#trigger()");

        Slog.i(TAG, "Triggering long method tracing for pid:" + pid);



        boolean result = nativeTrigger(pid, durationMs);

        if (!result) {

            Slog.w(TAG, "Failed to trigger long method tracing for pid " + pid);

        }

        Trace.traceEnd(TRACE_TAG_ACTIVITY_MANAGER);

        return result;

    }



    private static native boolean nativeTrigger(int pid, int durationMs);



}

services/core/java/com/android/server/utils/OWNERS

+3 −0
Original line number Diff line number Diff line
@@ -16,3 +16,6 @@ per-file LazyJniRegistrar.java = file:/PERFORMANCE_OWNERS 
per-file AnrTimer*.java = file:/PERFORMANCE_OWNERS



per-file flags.aconfig = file:/PERFORMANCE_OWNERS



# Long Method Tracing util

per-file LongMethodTracer.java = benmiles@google.com, ilkos@google.com, mohamadmahmoud@google.com
 
 No newline at end of file

services/core/java/com/android/server/utils/flags.aconfig

+8 −0
Original line number Diff line number Diff line
@@ -15,3 +15,11 @@ flag { 
     description: "Use AnrTimer to signal ANRs in JobScheduler"

     bug: "408440679"

}



flag {

     name: "long_method_trace"

     namespace: "stability"

     is_fixed_read_only: true

     description: "Enable long method tracing when true"

     bug: "419753987"

}
 
 No newline at end of file

services/core/jni/Android.bp

+1 −0
Original line number Diff line number Diff line
@@ -71,6 +71,7 @@ cc_library_static { 
        "com_android_server_am_LowMemDetector.cpp",

        "com_android_server_pm_PackageManagerShellCommandDataLoader.cpp",

        "com_android_server_sensor_SensorService.cpp",

        "com_android_server_utils_LongMethodTracer.cpp",

        "com_android_server_wm_TaskFpsCallbackController.cpp",

        "onload.cpp",

        ":lib_cachedAppOptimizer_native",

services/core/jni/OWNERS

+3 −0
Original line number Diff line number Diff line
@@ -41,3 +41,6 @@ per-file *AnrTimer* = file:/PERFORMANCE_OWNERS 


# HintManagerService

per-file com_android_server_hint_HintManagerService.cpp = file:/ADPF_OWNERS



# Long Method Tracer

per-file com_android_server_utils_LongMethodTracer.cpp = benmiles@google.com, ilkos@google.com, mohamadmahmoud@google.com
 
 No newline at end of file