From f0f9a829818a98236c81b96f9fe0f9ac3125eb1d Mon Sep 17 00:00:00 2001
From: Tim Murray <timmurray@google.com>
Date: Wed, 13 Jul 2016 13:33:28 -0700
Subject: [PATCH] Don't dump stack traces for background ANRs.

Dumping stack traces can be extremely expensive, and doing so for
background applications often has extremely negative side effects for
foreground applications. This can be exacerbated by resource-intensive
applications, because those may exhibit thermal throttling in the first
place. For such applications, the additional performance hit caused by
stack dumps may be catastrophic.

Instead, don't dump stack traces for background ANRs except for the app
that actually ANR'd.

bug 30112521

Change-Id: I8a05059343254861c436a193690cd1c50a95d674
---
 .../java/com/android/server/am/AppErrors.java | 64 +++++++++++--------
 1 file changed, 39 insertions(+), 25 deletions(-)

diff --git a/services/core/java/com/android/server/am/AppErrors.java b/services/core/java/com/android/server/am/AppErrors.java
index 49106f42044ec..cb37999b339e8 100644
--- a/services/core/java/com/android/server/am/AppErrors.java
+++ b/services/core/java/com/android/server/am/AppErrors.java
@@ -742,6 +742,12 @@ class AppErrors {
             mService.updateCpuStatsNow();
         }
 
+        // Unless configured otherwise, swallow ANRs in background processes & kill the process.
+        boolean showBackground = Settings.Secure.getInt(mContext.getContentResolver(),
+                Settings.Secure.ANR_SHOW_BACKGROUND, 0) != 0;
+
+        boolean isSilentANR;
+
         synchronized (mService) {
             // PowerManager.reboot() can block for a long time, so ignore ANRs while shutting down.
             if (mService.mShuttingDown) {
@@ -766,25 +772,29 @@ class AppErrors {
             // Dump thread traces as quickly as we can, starting with "interesting" processes.
             firstPids.add(app.pid);
 
-            int parentPid = app.pid;
-            if (parent != null && parent.app != null && parent.app.pid > 0) {
-                parentPid = parent.app.pid;
-            }
-            if (parentPid != app.pid) firstPids.add(parentPid);
+            // Don't dump other PIDs if it's a background ANR
+            isSilentANR = !showBackground && !app.isInterestingToUserLocked() && app.pid != MY_PID;
+            if (!isSilentANR) {
+                int parentPid = app.pid;
+                if (parent != null && parent.app != null && parent.app.pid > 0) {
+                    parentPid = parent.app.pid;
+                }
+                if (parentPid != app.pid) firstPids.add(parentPid);
 
-            if (MY_PID != app.pid && MY_PID != parentPid) firstPids.add(MY_PID);
+                if (MY_PID != app.pid && MY_PID != parentPid) firstPids.add(MY_PID);
 
-            for (int i = mService.mLruProcesses.size() - 1; i >= 0; i--) {
-                ProcessRecord r = mService.mLruProcesses.get(i);
-                if (r != null && r.thread != null) {
-                    int pid = r.pid;
-                    if (pid > 0 && pid != app.pid && pid != parentPid && pid != MY_PID) {
-                        if (r.persistent) {
-                            firstPids.add(pid);
-                            if (DEBUG_ANR) Slog.i(TAG, "Adding persistent proc: " + r);
-                        } else {
-                            lastPids.put(pid, Boolean.TRUE);
-                            if (DEBUG_ANR) Slog.i(TAG, "Adding ANR proc: " + r);
+                for (int i = mService.mLruProcesses.size() - 1; i >= 0; i--) {
+                    ProcessRecord r = mService.mLruProcesses.get(i);
+                    if (r != null && r.thread != null) {
+                        int pid = r.pid;
+                        if (pid > 0 && pid != app.pid && pid != parentPid && pid != MY_PID) {
+                            if (r.persistent) {
+                                firstPids.add(pid);
+                                if (DEBUG_ANR) Slog.i(TAG, "Adding persistent proc: " + r);
+                            } else {
+                                lastPids.put(pid, Boolean.TRUE);
+                                if (DEBUG_ANR) Slog.i(TAG, "Adding ANR proc: " + r);
+                            }
                         }
                     }
                 }
@@ -807,10 +817,18 @@ class AppErrors {
             info.append("Parent: ").append(parent.shortComponentName).append("\n");
         }
 
-        final ProcessCpuTracker processCpuTracker = new ProcessCpuTracker(true);
+        ProcessCpuTracker processCpuTracker = new ProcessCpuTracker(true);
 
-        File tracesFile = mService.dumpStackTraces(true, firstPids, processCpuTracker, lastPids,
-                NATIVE_STACKS_OF_INTEREST);
+        String[] nativeProcs = NATIVE_STACKS_OF_INTEREST;
+        // don't dump native PIDs for background ANRs
+        File tracesFile = null;
+        if (isSilentANR) {
+            tracesFile = mService.dumpStackTraces(true, firstPids, null, lastPids,
+                null);
+        } else {
+            tracesFile = mService.dumpStackTraces(true, firstPids, processCpuTracker, lastPids,
+                nativeProcs);
+        }
 
         String cpuInfo = null;
         if (ActivityManagerService.MONITOR_CPU_USAGE) {
@@ -854,14 +872,10 @@ class AppErrors {
             }
         }
 
-        // Unless configured otherwise, swallow ANRs in background processes & kill the process.
-        boolean showBackground = Settings.Secure.getInt(mContext.getContentResolver(),
-                Settings.Secure.ANR_SHOW_BACKGROUND, 0) != 0;
-
         synchronized (mService) {
             mService.mBatteryStatsService.noteProcessAnr(app.processName, app.uid);
 
-            if (!showBackground && !app.isInterestingToUserLocked() && app.pid != MY_PID) {
+            if (isSilentANR) {
                 app.kill("bg anr", true);
                 return;
             }