Handle thread preemption in debugger

src/debug.h

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 18 matching lines @@
 #define V8_V8_DEBUG_H_
 
 #include "../include/v8-debug.h"
 #include "assembler.h"
 #include "code-stubs.h"
 #include "debug-agent.h"
 #include "execution.h"
 #include "factory.h"
 #include "platform.h"
 #include "string-stream.h"
+#include "v8threads.h"
 
 
 namespace v8 { namespace internal {
 
+
+// Forward declarations.
+class EnterDebugger;
+
+
 // Step actions. NOTE: These values are in macros.py as well.
 enum StepAction {
   StepNone = -1,  // Stepping not prepared.
   StepOut = 0,   // Step out of the current function.
   StepNext = 1,  // Step to the next statement in the current function.
   StepIn = 2,    // Step into new functions invoked or the next statement
                  // in the current function.
   StepMin = 3,   // Perform a minimum step in the current function.
   StepInMin = 4  // Step into new functions invoked or perform a minimum step
                  // in the current function.
@@ skipping 106 matching lines @@
 // This class controls the debug info for all functions which currently have
 // active breakpoints in them. This debug info is held in the heap root object
 // debug_info which is a FixedArray. Each entry in this list is of class
 // DebugInfo.
 class Debug {
  public:
   static void Setup(bool create_heap_objects);
   static bool Load();
   static void Unload();
   static bool IsLoaded() { return !debug_context_.is_null(); }
-  static bool InDebugger() { return Top::is_break(); }
+  static bool InDebugger() { return thread_local_.debugger_entry_ != NULL; }
+  static void PreemptionWhileInDebugger();
   static void Iterate(ObjectVisitor* v);
 
   static Object* Break(Arguments args);
   static void SetBreakPoint(Handle<SharedFunctionInfo> shared,
                             int source_position,
                             Handle<Object> break_point_object);
   static void ClearBreakPoint(Handle<Object> break_point_object);
   static void ClearAllBreakPoints();
   static void FloodWithOneShot(Handle<SharedFunctionInfo> shared);
   static void FloodHandlerWithOneShot();
@@ skipping 24 matching lines @@
 
   // Getter for the debug_context.
   inline static Handle<Context> debug_context() { return debug_context_; }
 
   // Check whether a global object is the debug global object.
   static bool IsDebugGlobal(GlobalObject* global);
 
   // Fast check to see if any break points are active.
   inline static bool has_break_points() { return has_break_points_; }
 
+  static void NewBreak(StackFrame::Id break_frame_id);
+  static void SetBreak(StackFrame::Id break_frame_id, int break_id);
+  static StackFrame::Id break_frame_id() {
+    return thread_local_.break_frame_id_;
+  }
+  static int break_id() { return thread_local_.break_id_; }
+
+
+
+
   static bool StepInActive() { return thread_local_.step_into_fp_ != 0; }
   static void HandleStepIn(Handle<JSFunction> function,
                            Address fp,
                            bool is_constructor);
   static Address step_in_fp() { return thread_local_.step_into_fp_; }
   static Address* step_in_fp_addr() { return &thread_local_.step_into_fp_; }
 
+  static EnterDebugger* debugger_entry() {
+    return thread_local_.debugger_entry_;
+  }
+  static void set_debugger_entry(EnterDebugger* entry) {
+    thread_local_.debugger_entry_ = entry;
+  }
+
+  static bool preemption_pending() {
+    return thread_local_.preemption_pending_;
+  }
+  static void set_preemption_pending(bool preemption_pending) {
+    thread_local_.preemption_pending_ = preemption_pending;
+  }
+
   // Getter and setter for the disable break state.
   static bool disable_break() { return disable_break_; }
   static void set_disable_break(bool disable_break) {
     disable_break_ = disable_break;
   }
 
   // Getters for the current exception break state.
   static bool break_on_exception() { return break_on_exception_; }
   static bool break_on_uncaught_exception() {
     return break_on_uncaught_exception_;
@@ skipping 75 matching lines @@
   static Handle<Context> debug_context_;
 
   // Boolean state indicating whether any break points are set.
   static bool has_break_points_;
   static DebugInfoListNode* debug_info_list_;
 
   static bool disable_break_;
   static bool break_on_exception_;
   static bool break_on_uncaught_exception_;
 
-  // Per-thread:
+  // Per-thread data.
   class ThreadLocal {
    public:
+    // Counter for generating next break id.
+    int break_count_;
+
+    // Current break id.
+    int break_id_;
+
+    // Frame id for the frame of the current break.
+    StackFrame::Id break_frame_id_;
+
     // Step action for last step performed.
     StepAction last_step_action_;
 
     // Source statement position from last step next action.
     int last_statement_position_;
 
     // Number of steps left to perform before debug event.
     int step_count_;
 
     // Frame pointer from last step next action.
     Address last_fp_;
 
     // Frame pointer for frame from which step in was performed.
     Address step_into_fp_;
 
     // Storage location for jump when exiting debug break calls.
     Address after_break_target_;
+
+    // Top debugger entry.
+    EnterDebugger* debugger_entry_;
+
+    // Preemption happened while debugging.
+    bool preemption_pending_;
   };
 
   // Storage location for registers when handling debug break calls
   static JSCallerSavedBuffer registers_;
   static ThreadLocal thread_local_;
   static void ThreadInit();
 
   // Code object for debug break return entry code.
   static Code* debug_break_return_entry_;
 
@@ skipping 166 matching lines @@
   DISALLOW_COPY_AND_ASSIGN(DebugMessageThread);
 };
 
 
 // This class is used for entering the debugger. Create an instance in the stack
 // to enter the debugger. This will set the current break state, make sure the
 // debugger is loaded and switch to the debugger context. If the debugger for
 // some reason could not be entered FailedToEnter will return true.
 class EnterDebugger BASE_EMBEDDED {
  public:
-  EnterDebugger() : has_js_frames_(!it_.done()) {
+  EnterDebugger()
+      : prev_(Debug::debugger_entry()),
+        has_js_frames_(!it_.done()) {
+    ASSERT(!Debug::preemption_pending());
+
+    // Link recursive debugger entry.
+    Debug::set_debugger_entry(this);
+
+    // If a preemption is pending when first entering the debugger clear it as
+    // we don't want preemption happening while executing JavaScript in the
+    // debugger. When recursively entering the debugger the preemption flag
+    // cannot be set as this is disabled while in the debugger (see
+    // RuntimePreempt).
+    if (prev_ == NULL && StackGuard::IsPreempted()) {
+      StackGuard::Continue(PREEMPT);
+    }
+    ASSERT(!StackGuard::IsPreempted());
+
     // Store the previous break id and frame id.
-    break_id_ = Top::break_id();
-    break_frame_id_ = Top::break_frame_id();
+    break_id_ = Debug::break_id();
+    break_frame_id_ = Debug::break_frame_id();
 
     // Create the new break info. If there is no JavaScript frames there is no
     // break frame id.
     if (has_js_frames_) {
-      Top::new_break(it_.frame()->id());
+      Debug::NewBreak(it_.frame()->id());
     } else {
-      Top::new_break(StackFrame::NO_ID);
+      Debug::NewBreak(StackFrame::NO_ID);
     }
 
     // Make sure that debugger is loaded and enter the debugger context.
     load_failed_ = !Debug::Load();
     if (!load_failed_) {
       // NOTE the member variable save which saves the previous context before
       // this change.
       Top::set_context(*Debug::debug_context());
     }
   }
 
   ~EnterDebugger() {
     // Restore to the previous break state.
-    Top::set_break(break_frame_id_, break_id_);
+    Debug::SetBreak(break_frame_id_, break_id_);
+
+    // Request preemption when leaving the last debugger entry and a preemption
+    // had been recorded while debugging. This is to avoid starvation in some
+    // debugging scenarios.
+    if (prev_ == NULL && Debug::preemption_pending()) {
+      StackGuard::Preempt();
+      Debug::set_preemption_pending(false);
+    }
+  
+    // Leaving this debugger entry.
+    Debug::set_debugger_entry(prev_);
   }
 
   // Check whether the debugger could be entered.
   inline bool FailedToEnter() { return load_failed_; }
 
   // Check whether there are any JavaScript frames on the stack.
   inline bool HasJavaScriptFrames() { return has_js_frames_; }
 
  private:
+  EnterDebugger* prev_;  // Previous debugger entry if entered recursively.
   JavaScriptFrameIterator it_;
   const bool has_js_frames_;  // Were there any JavaScript frames?
   StackFrame::Id break_frame_id_;  // Previous break frame id.
   int break_id_;  // Previous break id.
   bool load_failed_;  // Did the debugger fail to load?
   SaveContext save_;  // Saves previous context.
 };
 
 
 // Stack allocated class for disabling break.
@@ skipping 52 matching lines @@
   }
  private:
   Debug::AddressId id_;
   int reg_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_V8_DEBUG_H_