Implement async AbortAll for the compiler dispatcher

src/cancelable-task.h

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_CANCELABLE_TASK_H_
 #define V8_CANCELABLE_TASK_H_
 
 #include <map>
 
 #include "include/v8-platform.h"
@@ skipping 27 matching lines @@
   // (3) The task is not yet running (or finished) so it is canceled and
   //     removed.
   //
   enum TryAbortResult { kTaskRemoved, kTaskRunning, kTaskAborted };
   TryAbortResult TryAbort(uint32_t id);
 
   // Cancels all remaining registered tasks and waits for tasks that are
   // already running. This disallows subsequent Register calls.
   void CancelAndWait();
 
+  // Tries to cancel all remaining registered tasks. The return value indicates
+  // whether
+  //
+  // 1) No tasks were registered (kTaskRemoved), or
+  //
+  // 2) There is at least one remaining task that couldn't be cancled
+  // (kTaskRunning), or
+  //
+  // 3) All registered tasks were cancelled (kTaskAborted).
+  TryAbortResult Cancel();

[marja, 2017/01/04 12:54:43]

The naming is confusing but it's there because of this CL...

We should either have:
TryAbort
TryAbortAllAndWait (now CancelAndWait)
TryAbortAll (now Cancel)

or:

Cancel (now TryAbort)
CancelAllAndWait (now CancelAndWait)
CancelAll (now Cancel)

wdyt? (But this probably shouldn't be fixed by this CL?)

[jochen (gone - plz use gerrit), 2017/01/04 13:18:31]

what about just renaming Cancel to TryAbortAll? CancelAll() doesn't try, it just
does - but the other two just try their best

+
  private:
   // Only called by {Cancelable} destructor. The task is done with executing,
   // but needs to be removed.
   void RemoveFinishedTask(uint32_t id);
 
   // To mitigate the ABA problem, the api refers to tasks through an id.
   uint32_t task_id_counter_;
 
   // A set of cancelable tasks that are currently registered.
   std::map<uint32_t, Cancelable*> cancelable_tasks_;
@@ skipping 107 matching lines @@
  private:
   Isolate* isolate_;
   DISALLOW_COPY_AND_ASSIGN(CancelableIdleTask);
 };
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_CANCELABLE_TASK_H_