Avoid race in single thread suspension.

Don't allow more than one concurrent single thread suspension to avoid
potential cycles and deadlocks where threads try to suspend each other.
Bug: 16364458, 16354227

Change-Id: I907f1d5591a6aa5c241d37d6b4a34f968f98df77

3 files changed, 20 insertions, 3 deletions

diff --git a/runtime/native/dalvik_system_VMStack.cc b/runtime/native/dalvik_system_VMStack.cc
index cf310648e5..5f718ba213 100644
--- a/runtime/native/dalvik_system_VMStack.cc
+++ b/runtime/native/dalvik_system_VMStack.cc
@@ -35,7 +35,12 @@ static jobject GetThreadStack(const ScopedFastNativeObjectAccess& soa, jobject p
     // Suspend thread to build stack trace.
     soa.Self()->TransitionFromRunnableToSuspended(kNative);
     bool timed_out;
-    Thread* thread = ThreadList::SuspendThreadByPeer(peer, true, false, &timed_out);
+    Thread* thread;
+    {
+      // Take suspend thread lock to avoid races with threads trying to suspend this one.
+      MutexLock mu(soa.Self(), *Locks::thread_list_suspend_thread_lock_);
+      thread = ThreadList::SuspendThreadByPeer(peer, true, false, &timed_out);
+    }
     if (thread != nullptr) {
       // Must be runnable to create returned array.
       CHECK_EQ(soa.Self()->TransitionFromSuspendedToRunnable(), kNative);
diff --git a/runtime/native/java_lang_Thread.cc b/runtime/native/java_lang_Thread.cc
index bae67f20e8..8f83f96318 100644
--- a/runtime/native/java_lang_Thread.cc
+++ b/runtime/native/java_lang_Thread.cc
@@ -116,18 +116,25 @@ static void Thread_nativeInterrupt(JNIEnv* env, jobject java_thread) {
 
 static void Thread_nativeSetName(JNIEnv* env, jobject peer, jstring java_name) {
   ScopedUtfChars name(env, java_name);
+  Thread* self;
   {
     ScopedObjectAccess soa(env);
     if (soa.Decode<mirror::Object*>(peer) == soa.Self()->GetPeer()) {
       soa.Self()->SetThreadName(name.c_str());
       return;
     }
+    self = soa.Self();
   }
   // Suspend thread to avoid it from killing itself while we set its name. We don't just hold the
   // thread list lock to avoid this, as setting the thread name causes mutator to lock/unlock
   // in the DDMS send code.
   bool timed_out;
-  Thread* thread = ThreadList::SuspendThreadByPeer(peer, true, false, &timed_out);
+  // Take suspend thread lock to avoid races with threads trying to suspend this one.
+  Thread* thread;
+  {
+    MutexLock mu(self, *Locks::thread_list_suspend_thread_lock_);
+    thread = ThreadList::SuspendThreadByPeer(peer, true, false, &timed_out);
+  }
   if (thread != NULL) {
     {
       ScopedObjectAccess soa(env);
diff --git a/runtime/native/org_apache_harmony_dalvik_ddmc_DdmVmInternal.cc b/runtime/native/org_apache_harmony_dalvik_ddmc_DdmVmInternal.cc
index e17e60a7ce..45ef9ae727 100644
--- a/runtime/native/org_apache_harmony_dalvik_ddmc_DdmVmInternal.cc
+++ b/runtime/native/org_apache_harmony_dalvik_ddmc_DdmVmInternal.cc
@@ -61,7 +61,12 @@ static jobjectArray DdmVmInternal_getStackTraceById(JNIEnv* env, jclass, jint th
     }
 
     // Suspend thread to build stack trace.
-    Thread* thread = thread_list->SuspendThreadByThreadId(thin_lock_id, false, &timed_out);
+    Thread* thread;
+    {
+      // Take suspend thread lock to avoid races with threads trying to suspend this one.
+      MutexLock mu(self, *Locks::thread_list_suspend_thread_lock_);
+      thread = thread_list->SuspendThreadByThreadId(thin_lock_id, false, &timed_out);
+    }
     if (thread != nullptr) {
       {
         ScopedObjectAccess soa(env);