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 <map>
#include <memory>
#include <set>

#include "base/atomicops.h"
#include "base/containers/hash_tables.h"
#include "base/memory/ref_counted.h"
#include "base/memory/singleton.h"
#include "base/synchronization/lock.h"
#include "base/timer/timer.h"
#include "base/trace_event/memory_dump_request_args.h"
#include "base/trace_event/process_memory_dump.h"
#include "base/trace_event/trace_event.h"

namespace base {

class SingleThreadTaskRunner;
class Thread;

namespace trace_event {

class MemoryDumpManagerDelegate;
class MemoryDumpProvider;
class MemoryDumpSessionState;

// This is the interface exposed to the rest of the codebase to deal with
// memory tracing. The main entry point for clients is represented by
// RequestDumpPoint(). The extension by Un(RegisterDumpProvider).
class BASE_EXPORT MemoryDumpManager : public TraceLog::EnabledStateObserver {
 public:
  static const char* const kTraceCategory;

  // This value is returned as the tracing id of the child processes by
  // GetTracingProcessId() when tracing is not enabled.
  static const uint64_t kInvalidTracingProcessId;

  static MemoryDumpManager* GetInstance();

  // Invoked once per process to listen to trace begin / end events.
  // Initialization can happen after (Un)RegisterMemoryDumpProvider() calls
  // and the MemoryDumpManager guarantees to support this.
  // On the other side, the MemoryDumpManager will not be fully operational
  // (i.e. will NACK any RequestGlobalMemoryDump()) until initialized.
  // Arguments:
  //  is_coordinator: if true this MemoryDumpManager instance will act as a
  //      coordinator and schedule periodic dumps (if enabled via TraceConfig);
  //      false when the MemoryDumpManager is initialized in a slave process.
  //  delegate: inversion-of-control interface for embedder-specific behaviors
  //      (multiprocess handshaking). See the lifetime and thread-safety
  //      requirements in the |MemoryDumpManagerDelegate| docstring.
  void Initialize(MemoryDumpManagerDelegate* delegate, bool is_coordinator);

  // (Un)Registers a MemoryDumpProvider instance.
  // Args:
  //  - mdp: the MemoryDumpProvider instance to be registered. MemoryDumpManager
  //      does NOT take memory ownership of |mdp|, which is expected to either
  //      be a singleton or unregister itself.
  //  - name: a friendly name (duplicates allowed). Used for debugging and
  //      run-time profiling of memory-infra internals. Must be a long-lived
  //      C string.
  //  - task_runner: if non-null, all the calls to |mdp| will be
  //      issued on the given thread. Otherwise, |mdp| should be able to
  //      handle calls on arbitrary threads.
  //  - options: extra optional arguments. See memory_dump_provider.h.
  void RegisterDumpProvider(
      MemoryDumpProvider* mdp,
      const char* name,
      const scoped_refptr<SingleThreadTaskRunner>& task_runner);
  void RegisterDumpProvider(
      MemoryDumpProvider* mdp,
      const char* name,
      const scoped_refptr<SingleThreadTaskRunner>& task_runner,
      const MemoryDumpProvider::Options& options);
  void UnregisterDumpProvider(MemoryDumpProvider* mdp);

  // Requests a memory dump. The dump might happen or not depending on the
  // filters and categories specified when enabling tracing.
  // The optional |callback| is executed asynchronously, on an arbitrary thread,
  // to notify about the completion of the global dump (i.e. after all the
  // processes have dumped) and its success (true iff all the dumps were
  // successful).
  void RequestGlobalDump(MemoryDumpType dump_type,
                         MemoryDumpLevelOfDetail level_of_detail,
                         const MemoryDumpCallback& callback);

  // Same as above (still asynchronous), but without callback.
  void RequestGlobalDump(MemoryDumpType dump_type,
                         MemoryDumpLevelOfDetail level_of_detail);

  // TraceLog::EnabledStateObserver implementation.
  void OnTraceLogEnabled() override;
  void OnTraceLogDisabled() override;

  // Returns the MemoryDumpSessionState object, which is shared by all the
  // ProcessMemoryDump and MemoryAllocatorDump instances through all the tracing
  // session lifetime.
  const scoped_refptr<MemoryDumpSessionState>& session_state() const {
    return session_state_;
  }

  // Returns a unique id for identifying the processes. The id can be
  // retrieved by child processes only when tracing is enabled. This is
  // intended to express cross-process sharing of memory dumps on the
  // child-process side, without having to know its own child process id.
  uint64_t GetTracingProcessId() const;

  // Returns the name for a the allocated_objects dump. Use this to declare
  // suballocator dumps from other dump providers.
  // It will return nullptr if there is no dump provider for the system
  // allocator registered (which is currently the case for Mac OS).
  const char* system_allocator_pool_name() const {
    return kSystemAllocatorPoolName;
  };

  // When set to true, calling |RegisterMemoryDumpProvider| is a no-op.
  void set_dumper_registrations_ignored_for_testing(bool ignored) {
    dumper_registrations_ignored_for_testing_ = ignored;
  }

 private:
  friend std::default_delete<MemoryDumpManager>;  // For the testing instance.
  friend struct DefaultSingletonTraits<MemoryDumpManager>;
  friend class MemoryDumpManagerDelegate;
  friend class MemoryDumpManagerTest;

  // 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 char* name,
        const scoped_refptr<SingleThreadTaskRunner>& task_runner,
        const MemoryDumpProvider::Options& options);
    ~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;
    const char* const name;

    // The task_runner affinity. Can be nullptr, in which case the dump provider
    // will be invoked on |dump_thread_|.
    scoped_refptr<SingleThreadTaskRunner> task_runner;

    // The |options| arg passed to RegisterDumpProvider().
    const MemoryDumpProvider::Options options;

    // 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,
        MemoryDumpProviderInfoSet::iterator next_dump_provider,
        const scoped_refptr<MemoryDumpSessionState>& session_state,
        MemoryDumpCallback callback,
        const scoped_refptr<SingleThreadTaskRunner>& dump_thread_task_runner);
    ~ProcessMemoryDumpAsyncState();

    // Gets or creates the memory dump container for the given target process.
    ProcessMemoryDump* GetOrCreateMemoryDumpContainerForProcess(ProcessId pid);

    // A map of ProcessId -> ProcessMemoryDump, one for each target process
    // being dumped from the current process. Typically each process dumps only
    // for itself, unless dump providers specify a different |target_process| in
    // MemoryDumpProvider::Options.
    std::map<ProcessId, scoped_ptr<ProcessMemoryDump>> process_dumps;

    // The arguments passed to the initial CreateProcessDump() request.
    const MemoryDumpRequestArgs req_args;

    // The |dump_providers_| iterator to the next dump provider that should be
    // invoked (or dump_providers_.end() if at the end of the sequence).
    MemoryDumpProviderInfoSet::iterator next_dump_provider;

    // The trace-global session state.
    scoped_refptr<MemoryDumpSessionState> session_state;

    // Callback passed to the initial call to CreateProcessDump().
    MemoryDumpCallback callback;

    // The thread on which FinalizeDumpAndAddToTrace() (and hence |callback|)
    // should be invoked. This is the thread on which the initial
    // CreateProcessDump() request was called.
    const scoped_refptr<SingleThreadTaskRunner> callback_task_runner;

    // The thread on which unbound dump providers should be invoked.
    // This is essentially |dump_thread_|.task_runner() but needs to be kept
    // as a separate variable as it needs to be accessed by arbitrary dumpers'
    // threads outside of the lock_ to avoid races when disabling tracing.
    // It is immutable for all the duration of a tracing session.
    const scoped_refptr<SingleThreadTaskRunner> dump_thread_task_runner;

   private:
    DISALLOW_COPY_AND_ASSIGN(ProcessMemoryDumpAsyncState);
  };

  static const int kMaxConsecutiveFailuresCount;
  static const char* const kSystemAllocatorPoolName;

  MemoryDumpManager();
  ~MemoryDumpManager() override;

  static void SetInstanceForTesting(MemoryDumpManager* instance);
  static void FinalizeDumpAndAddToTrace(
      scoped_ptr<ProcessMemoryDumpAsyncState> pmd_async_state);
  static void AbortDumpLocked(MemoryDumpCallback callback,
                              scoped_refptr<SingleThreadTaskRunner> task_runner,
                              uint64_t dump_guid);

  // Internal, used only by MemoryDumpManagerDelegate.
  // Creates a memory dump for the current process and appends it to the trace.
  // |callback| will be invoked asynchronously upon completion on the same
  // thread on which CreateProcessDump() was called.
  void CreateProcessDump(const MemoryDumpRequestArgs& args,
                         const MemoryDumpCallback& callback);

  // 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_;

  // Shared among all the PMDs to keep state scoped to the tracing session.
  scoped_refptr<MemoryDumpSessionState> session_state_;

  MemoryDumpManagerDelegate* delegate_;  // Not owned.

  // When true, this instance is in charge of coordinating periodic dumps.
  bool is_coordinator_;

  // 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
  // dump_providers_enabled_ list) when tracing is not enabled.
  subtle::AtomicWord memory_tracing_enabled_;

  // For time-triggered periodic dumps.
  RepeatingTimer periodic_dump_timer_;

  // Thread used for MemoryDumpProviders which don't specify a thread affinity.
  scoped_ptr<Thread> dump_thread_;

  // The unique id of the child process. This is created only for tracing and is
  // expected to be valid only when tracing is enabled.
  uint64_t tracing_process_id_;

  // When true, calling |RegisterMemoryDumpProvider| is a no-op.
  bool dumper_registrations_ignored_for_testing_;

  // Whether new memory dump providers should be told to enable heap profiling.
  bool heap_profiling_enabled_;

  DISALLOW_COPY_AND_ASSIGN(MemoryDumpManager);
};

// The delegate is supposed to be long lived (read: a Singleton) and thread
// safe (i.e. should expect calls from any thread and handle thread hopping).
class BASE_EXPORT MemoryDumpManagerDelegate {
 public:
  virtual void RequestGlobalMemoryDump(const MemoryDumpRequestArgs& args,
                                       const MemoryDumpCallback& callback) = 0;

  // Returns tracing process id of the current process. This is used by
  // MemoryDumpManager::GetTracingProcessId.
  virtual uint64_t GetTracingProcessId() const = 0;

 protected:
  MemoryDumpManagerDelegate() {}
  virtual ~MemoryDumpManagerDelegate() {}

  void CreateProcessDump(const MemoryDumpRequestArgs& args,
                         const MemoryDumpCallback& callback) {
    MemoryDumpManager::GetInstance()->CreateProcessDump(args, callback);
  }

 private:
  DISALLOW_COPY_AND_ASSIGN(MemoryDumpManagerDelegate);
};

}  // namespace trace_event
}  // namespace base

#endif  // BASE_TRACE_EVENT_MEMORY_DUMP_MANAGER_H_