commit af8bcf83535cd7bf5651ada2fb08a0ba9c5191d6
author Sebastien Hertz <shertz@google.com> Tue Nov 22 14:55:04 2016 +0100
committer Sebastien Hertz <shertz@google.com> Tue Nov 29 11:51:03 2016 +0100
tree f029668c26269484652e9432fab3a246be81d2e7
parent da2d78ba97d177b80e0e9528362bcebc1fd31f0f

Fix event reporting from the debugger thread

The debugger thread may trigger events (like CLASS PREPARE after the
initalization of a class while processing a command).

This CL removes the incorrect CHECK that makes the runtime abort in
this case. However, we do check that only the debugger thread can
report an event while it is already processing a command.

Bug: 33032664
Test: art/tools/run-jdwp-tests.sh '--mode=host' '--variant=X64'
Change-Id: I32a284cfb4df6eb44eac27bbdcabd3c426d726ce

runtime/jdwp/jdwp_event.cc

diff --git a/runtime/jdwp/jdwp_event.cc b/runtime/jdwp/jdwp_event.cc
index fad7d90..5574a11 100644
--- a/runtime/jdwp/jdwp_event.cc
+++ b/runtime/jdwp/jdwp_event.cc
@@ -621,8 +621,8 @@
   Thread* const self = Thread::Current();
   self->AssertThreadSuspensionIsAllowable();
   CHECK(pReq != nullptr);
+  CHECK_EQ(threadId, Dbg::GetThreadSelfId()) << "Only the current thread can suspend itself";
   /* send request and possibly suspend ourselves */
-  JDWP::ObjectId thread_self_id = Dbg::GetThreadSelfId();
   ScopedThreadSuspension sts(self, kWaitingForDebuggerSend);
   if (suspend_policy != SP_NONE) {
     AcquireJdwpTokenForEvent(threadId);
@@ -631,7 +631,7 @@
   {
     // Before suspending, we change our state to kSuspended so the debugger sees us as RUNNING.
     ScopedThreadStateChange stsc(self, kSuspended);
-    SuspendByPolicy(suspend_policy, thread_self_id);
+    SuspendByPolicy(suspend_policy, threadId);
   }
 }
 
@@ -658,13 +658,10 @@
 }
 
 void JdwpState::AcquireJdwpTokenForEvent(ObjectId threadId) {
-  CHECK_NE(Thread::Current(), GetDebugThread()) << "Expected event thread";
-  CHECK_NE(debug_thread_id_, threadId) << "Not expected debug thread";
   SetWaitForJdwpToken(threadId);
 }
 
 void JdwpState::ReleaseJdwpTokenForEvent() {
-  CHECK_NE(Thread::Current(), GetDebugThread()) << "Expected event thread";
   ClearWaitForJdwpToken();
 }
 
@@ -685,23 +682,28 @@
   /* this is held for very brief periods; contention is unlikely */
   MutexLock mu(self, jdwp_token_lock_);
 
-  CHECK_NE(jdwp_token_owner_thread_id_, threadId) << "Thread is already holding event thread lock";
+  if (jdwp_token_owner_thread_id_ == threadId) {
+    // Only the debugger thread may already hold the event token. For instance, it may trigger
+    // a CLASS_PREPARE event while processing a command that initializes a class.
+    CHECK_EQ(threadId, debug_thread_id_) << "Non-debugger thread is already holding event token";
+  } else {
+    /*
+     * If another thread is already doing stuff, wait for it.  This can
+     * go to sleep indefinitely.
+     */
 
-  /*
-   * If another thread is already doing stuff, wait for it.  This can
-   * go to sleep indefinitely.
-   */
-  while (jdwp_token_owner_thread_id_ != 0) {
-    VLOG(jdwp) << StringPrintf("event in progress (%#" PRIx64 "), %#" PRIx64 " sleeping",
-                               jdwp_token_owner_thread_id_, threadId);
-    waited = true;
-    jdwp_token_cond_.Wait(self);
-  }
+    while (jdwp_token_owner_thread_id_ != 0) {
+      VLOG(jdwp) << StringPrintf("event in progress (%#" PRIx64 "), %#" PRIx64 " sleeping",
+                                 jdwp_token_owner_thread_id_, threadId);
+      waited = true;
+      jdwp_token_cond_.Wait(self);
+    }
 
-  if (waited || threadId != debug_thread_id_) {
-    VLOG(jdwp) << StringPrintf("event token grabbed (%#" PRIx64 ")", threadId);
+    if (waited || threadId != debug_thread_id_) {
+      VLOG(jdwp) << StringPrintf("event token grabbed (%#" PRIx64 ")", threadId);
+    }
+    jdwp_token_owner_thread_id_ = threadId;
   }
-  jdwp_token_owner_thread_id_ = threadId;
 }
 
 /*
@@ -1224,14 +1226,15 @@
     VLOG(jdwp) << "  suspend_policy=" << suspend_policy;
   }
 
-  if (thread_id == debug_thread_id_) {
+  ObjectId reported_thread_id = thread_id;
+  if (reported_thread_id == debug_thread_id_) {
     /*
      * JDWP says that, for a class prep in the debugger thread, we
      * should set thread to null and if any threads were supposed
      * to be suspended then we suspend all other threads.
      */
     VLOG(jdwp) << "  NOTE: class prepare in debugger thread!";
-    thread_id = 0;
+    reported_thread_id = 0;
     if (suspend_policy == SP_EVENT_THREAD) {
       suspend_policy = SP_ALL;
     }
@@ -1244,7 +1247,7 @@
   for (const JdwpEvent* pEvent : match_list) {
     expandBufAdd1(pReq, pEvent->eventKind);
     expandBufAdd4BE(pReq, pEvent->requestId);
-    expandBufAddObjectId(pReq, thread_id);
+    expandBufAddObjectId(pReq, reported_thread_id);
     expandBufAdd1(pReq, tag);
     expandBufAddRefTypeId(pReq, class_id);
     expandBufAddUtf8String(pReq, signature);