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Commit 5df1d871 authored by Colin Cross's avatar Colin Cross
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trigger kernel blocked stack trace on system server watchdog 

Bug b/7638530 may be caused by a kernel deadlock when killing
processes under low memory conditions.  Write to /proc/sysrq-trigger
to get a kernel log of blocked tasks before killing the system server.

Bug: 7638530
Change-Id: I60df324ad4affdadbf13650099dc4dfb38722420
parent 154e2d7d

services/java/com/android/server/Watchdog.java

+12 −0
Original line number Diff line number Diff line
@@ -39,6 +39,8 @@ import android.util.Log; 
import android.util.Slog;



import java.io.File;

import java.io.FileWriter;

import java.io.IOException;

import java.util.ArrayList;

import java.util.Calendar;
@@ -439,6 +441,16 @@ public class Watchdog extends Thread { 
                dumpKernelStackTraces();

            }



            // Trigger the kernel to dump all blocked threads to the kernel log

            try {

                FileWriter sysrq_trigger = new FileWriter("/proc/sysrq-trigger");

                sysrq_trigger.write("w");

                sysrq_trigger.close();

            } catch (IOException e) {

                Slog.e(TAG, "Failed to write to /proc/sysrq-trigger");

                Slog.e(TAG, e.getMessage());

            }



            // Try to add the error to the dropbox, but assuming that the ActivityManager

            // itself may be deadlocked.  (which has happened, causing this statement to

            // deadlock and the watchdog as a whole to be ineffective)