Allow unregistering MemoryDumpProviders during dump

base/trace_event/memory_dump_manager.h

 // Copyright 2015 The Chromium 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 BASE_TRACE_EVENT_MEMORY_DUMP_MANAGER_H_
 #define BASE_TRACE_EVENT_MEMORY_DUMP_MANAGER_H_
 
 #include <set>
 
 #include "base/atomicops.h"
@@ skipping 85 matching lines @@
   const char* system_allocator_pool_name() const {
     return system_allocator_pool_name_;
   };
 
  private:
   friend struct DefaultDeleter<MemoryDumpManager>;  // For the testing instance.
   friend struct DefaultSingletonTraits<MemoryDumpManager>;
   friend class MemoryDumpManagerDelegate;
   friend class MemoryDumpManagerTest;
   FRIEND_TEST_ALL_PREFIXES(MemoryDumpManagerTest, DisableFailingDumpers);
+  FRIEND_TEST_ALL_PREFIXES(MemoryDumpManagerTest,
+                           UnregisterDumperFromThreadWhileDumping);
 
   // Descriptor struct used to hold information about registered MDPs. It is
   // deliberately copyable, in order to allow it to be used as std::set value.
   struct MemoryDumpProviderInfo {
     MemoryDumpProviderInfo(
         MemoryDumpProvider* dump_provider,
         const scoped_refptr<SingleThreadTaskRunner>& task_runner);
     ~MemoryDumpProviderInfo();
 
     // Define a total order based on the thread (i.e. |task_runner|) affinity,
     // so that all MDP belonging to the same thread are adjacent in the set.
     bool operator<(const MemoryDumpProviderInfo& other) const;
 
     MemoryDumpProvider* const dump_provider;
     scoped_refptr<SingleThreadTaskRunner> task_runner;  // Optional.
 
     // For fail-safe logic (auto-disable failing MDPs). These fields are mutable
     // as can be safely changed without impacting the order within the set.
     mutable int consecutive_failures;
     mutable bool disabled;
+
+    // When a dump provider unregisters, it is flagged as |unregistered| and it
+    // is removed only upon the next memory dump. This is to avoid altering the
+    // |dump_providers_| collection while a dump is in progress.
+    mutable bool unregistered;
   };
 
   using MemoryDumpProviderInfoSet = std::set<MemoryDumpProviderInfo>;
 
   // Holds the state of a process memory dump that needs to be carried over
   // across threads in order to fulfil an asynchronous CreateProcessDump()
   // request. At any time exactly one thread owns a ProcessMemoryDumpAsyncState.
   struct ProcessMemoryDumpAsyncState {
     ProcessMemoryDumpAsyncState(
         MemoryDumpRequestArgs req_args,
@@ skipping 46 matching lines @@
 
   // Continues the ProcessMemoryDump started by CreateProcessDump(), hopping
   // across threads as needed as specified by MDPs in RegisterDumpProvider().
   void ContinueAsyncProcessDump(
       scoped_ptr<ProcessMemoryDumpAsyncState> pmd_async_state);
 
   // An ordererd set of registered MemoryDumpProviderInfo(s), sorted by thread
   // affinity (MDPs belonging to the same thread are adjacent).
   MemoryDumpProviderInfoSet dump_providers_;
 
-  // Flag used to signal that some provider was removed from |dump_providers_|
-  // and therefore the current memory dump (if any) should be aborted.
-  bool did_unregister_dump_provider_;
-
   // Shared among all the PMDs to keep state scoped to the tracing session.
   scoped_refptr<MemoryDumpSessionState> session_state_;
 
   MemoryDumpManagerDelegate* delegate_;  // Not owned.
 
   // Protects from concurrent accesses to the |dump_providers_*| and |delegate_|
   // to guard against disabling logging while dumping on another thread.
   Lock lock_;
 
   // Optimization to avoid attempting any memory dump (i.e. to not walk an empty
@@ skipping 41 matching lines @@
   }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(MemoryDumpManagerDelegate);
 };
 
 }  // namespace trace_event
 }  // namespace base
 
 #endif  // BASE_TRACE_EVENT_MEMORY_DUMP_MANAGER_H_