commit 8f95cf3cb5f715b1277de9cd7fade07ce4b230be
author Hiroshi Yamauchi <yamauchi@google.com> Tue Apr 19 11:14:06 2016 -0700
committer Hiroshi Yamauchi <yamauchi@google.com> Tue Apr 19 11:17:09 2016 -0700
tree b66e14b2df428fed5117caa709bc70462d351892
parent defccc564481c2c892792680c6abb6020e36bacd

Fix a deadlock between debugger and GC.

Avoid a deadlock between GC and debugger's SuspendAllForDebugger where
GC gets suspended during GC.

Fix the jdwp tests with the CC collector, but the deadlock is NOT
specific to the CC collector.

Bug: 25800335
Bug: 12687968
Change-Id: I8f2869872bce4692d943020072e35ebf5a4e68a5

runtime/debugger.cc

diff --git a/runtime/debugger.cc b/runtime/debugger.cc
index d832552..55f68d3 100644
--- a/runtime/debugger.cc
+++ b/runtime/debugger.cc
@@ -2362,6 +2362,10 @@
 }
 
 void Dbg::SuspendVM() {
+  // Avoid a deadlock between GC and debugger where GC gets suspended during GC. b/25800335.
+  gc::ScopedGCCriticalSection gcs(Thread::Current(),
+                                  gc::kGcCauseDebugger,
+                                  gc::kCollectorTypeDebugger);
   Runtime::Current()->GetThreadList()->SuspendAllForDebugger();
 }
 
@@ -4101,6 +4105,8 @@
   // Suspend other threads if the invoke is not single-threaded.
   if ((pReq->options & JDWP::INVOKE_SINGLE_THREADED) == 0) {
     ScopedThreadSuspension sts(soa.Self(), kWaitingForDebuggerSuspension);
+    // Avoid a deadlock between GC and debugger where GC gets suspended during GC. b/25800335.
+    gc::ScopedGCCriticalSection gcs(soa.Self(), gc::kGcCauseDebugger, gc::kCollectorTypeDebugger);
     VLOG(jdwp) << "      Suspending all threads";
     Runtime::Current()->GetThreadList()->SuspendAllForDebugger();
   }

runtime/gc/collector_type.h

diff --git a/runtime/gc/collector_type.h b/runtime/gc/collector_type.h
index ae41226..4ffc8af 100644
--- a/runtime/gc/collector_type.h
+++ b/runtime/gc/collector_type.h
@@ -44,6 +44,8 @@
   kCollectorTypeInstrumentation,
   // Fake collector for adding or removing application image spaces.
   kCollectorTypeAddRemoveAppImageSpace,
+  // Fake collector used to implement exclusion between GC and debugger.
+  kCollectorTypeDebugger,
   // A homogeneous space compaction collector used in background transition
   // when both foreground and background collector are CMS.
   kCollectorTypeHomogeneousSpaceCompact,

runtime/gc/gc_cause.cc

diff --git a/runtime/gc/gc_cause.cc b/runtime/gc/gc_cause.cc
index 679432b..18e5703 100644
--- a/runtime/gc/gc_cause.cc
+++ b/runtime/gc/gc_cause.cc
@@ -35,6 +35,7 @@
     case kGcCauseTrim: return "HeapTrim";
     case kGcCauseInstrumentation: return "Instrumentation";
     case kGcCauseAddRemoveAppImageSpace: return "AddRemoveAppImageSpace";
+    case kGcCauseDebugger: return "Debugger";
     default:
       LOG(FATAL) << "Unreachable";
       UNREACHABLE();

runtime/gc/gc_cause.h

diff --git a/runtime/gc/gc_cause.h b/runtime/gc/gc_cause.h
index c6b505c..ad67eb7 100644
--- a/runtime/gc/gc_cause.h
+++ b/runtime/gc/gc_cause.h
@@ -43,6 +43,8 @@
   kGcCauseInstrumentation,
   // Not a real GC cause, used to add or remove app image spaces.
   kGcCauseAddRemoveAppImageSpace,
+  // Not a real GC cause, used to implement exclusion between GC and debugger.
+  kGcCauseDebugger,
   // GC triggered for background transition when both foreground and background collector are CMS.
   kGcCauseHomogeneousSpaceCompact,
 };