Improve the ThreadStress test to send SIGQUIT, and fix the bug that finds.

I'd heard complaints of a system_server deadlock on crespo, but wasn't seeing
it on mysid. I did see it soon after trying to use crespo, but system_server
has way too many threads and adb is too damn unreliable for me to effectively
debug that. This improves ThreadStress so we exercise that path lots, and
catch the deadlock relatively quickly with relatively few threads.

The fix is explained in a code comment that's larger than the fix.

Change-Id: I593bc94cf1239065a604703568420986a03ce628

2 files changed, 15 insertions, 1 deletions

diff --git a/src/signal_catcher.cc b/src/signal_catcher.cc
index 9031c5e55f..80563e2bf4 100644
--- a/src/signal_catcher.cc
+++ b/src/signal_catcher.cc
@@ -95,6 +95,12 @@ void SignalCatcher::HandleSigQuit() {
   Runtime* runtime = Runtime::Current();
   ThreadList* thread_list = runtime->GetThreadList();
 
+  // We take the heap lock before suspending all threads so we don't end up in a situation where
+  // one of the suspended threads suspended via the implicit FullSuspendCheck on the slow path of
+  // Heap::Lock, which is the only case where a thread can be suspended while holding the heap lock.
+  // (We need the heap lock when we dump the thread list. We could probably fix this by duplicating
+  // more state from java.lang.Thread in struct Thread.)
+  ScopedHeapLock heap_lock;
   thread_list->SuspendAll();
 
   std::ostringstream os;
diff --git a/test/ThreadStress/ThreadStress.java b/test/ThreadStress/ThreadStress.java
index c294a3861a..1f8fb2d922 100644
--- a/test/ThreadStress/ThreadStress.java
+++ b/test/ThreadStress/ThreadStress.java
@@ -20,6 +20,7 @@ import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import libcore.io.*;
 
 // Run on host with:
 //   javac ThreadTest.java && java ThreadStress && rm *.class
@@ -29,7 +30,8 @@ class ThreadStress implements Runnable {
 
     enum Operation {
         OOM(1),
-        ALLOC(99),
+        SIGQUIT(19),
+        ALLOC(80),
         EXIT(50),
         WAIT(50);
 
@@ -194,6 +196,12 @@ class ThreadStress implements Runnable {
                     case EXIT: {
                         return;
                     }
+                    case SIGQUIT: {
+                        try {
+                            Libcore.os.kill(Libcore.os.getpid(), OsConstants.SIGQUIT);
+                        } catch (ErrnoException ex) {
+                        }
+                    }
                     case WAIT: {
                         synchronized (lock) {
                             try {