[vm] Make the crash reporter more resilient to crashes during safepoints.

runtime/vm/profiler.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/address_sanitizer.h"
 #include "platform/memory_sanitizer.h"
 #include "platform/utils.h"
 
 #include "vm/allocation.h"
 #include "vm/atomic.h"
@@ skipping 388 matching lines @@
 }
 
 ClearProfileVisitor::ClearProfileVisitor(Isolate* isolate)
     : SampleVisitor(isolate->main_port()) {}
 
 void ClearProfileVisitor::VisitSample(Sample* sample) {
   sample->Clear();
 }
 
 static void DumpStackFrame(intptr_t frame_index, uword pc) {
-  Isolate* isolate = Isolate::Current();
-  if ((isolate != NULL) && isolate->is_runnable()) {
-    Code& code = Code::Handle(Code::LookupCodeInVmIsolate(pc));
-    if (!code.IsNull()) {
-      OS::PrintErr("  [0x%" Pp "] %s\n", pc, code.QualifiedName());
-      return;
-    }
-    code = Code::LookupCode(pc);
-    if (!code.IsNull()) {
-      OS::PrintErr("  [0x%" Pp "] %s\n", pc, code.QualifiedName());
-      return;
+  Thread* thread = Thread::Current();
+  if ((thread != NULL) && !thread->IsAtSafepoint()) {
+    Isolate* isolate = thread->isolate();
+    if ((isolate != NULL) && isolate->is_runnable()) {
+      // Attempt to symbolize Dart frames if we have can safely iterate the
+      // current isolate's heap.

[danunez, 2017/08/08 20:44:02]

This comment is unclear to me. It reads like there is a word missing.

[rmacnak, 2017/08/09 17:58:39]

Deleted "have"

+      Code& code = Code::Handle(Code::LookupCodeInVmIsolate(pc));
+      if (!code.IsNull()) {
+        OS::PrintErr("  [0x%" Pp "] %s\n", pc, code.QualifiedName());
+        return;
+      }
+      code = Code::LookupCode(pc);
+      if (!code.IsNull()) {
+        OS::PrintErr("  [0x%" Pp "] %s\n", pc, code.QualifiedName());
+        return;
+      }

[siva, 2017/08/08 23:59:55]

why not 

Code& code = Code::Handle(Code::LookupCodeInVmIsolate(pc));
if (code.IsNull()) {
  code = Code::LookupCode(pc);
}
if (!code.IsNull()) {
  OS::PrintErr("  [0x%" Pp "] %s\n", pc, code.QualifiedName());
  return;
}

[rmacnak, 2017/08/09 17:58:39]

Done.

     }
   }
 
   uintptr_t start = 0;
   char* native_symbol_name = NativeSymbolResolver::LookupSymbolName(pc, &start);
   if (native_symbol_name == NULL) {
     OS::PrintErr("  [0x%" Pp "] Unknown symbol\n", pc);
   } else {
     OS::PrintErr("  [0x%" Pp "] %s\n", pc, native_symbol_name);
     NativeSymbolResolver::FreeSymbolName(native_symbol_name);
@@ skipping 1254 matching lines @@
 }
 
 ProcessedSampleBuffer::ProcessedSampleBuffer()
     : code_lookup_table_(new CodeLookupTable(Thread::Current())) {
   ASSERT(code_lookup_table_ != NULL);
 }
 
 #endif  // !PRODUCT
 
 }  // namespace dart