metrics: Connect leak detector to allocator

components/metrics/leak_detector/leak_detector.h

 // Copyright 2016 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 COMPONENTS_METRICS_LEAK_DETECTOR_LEAK_DETECTOR_H_
 #define COMPONENTS_METRICS_LEAK_DETECTOR_LEAK_DETECTOR_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <list>
 #include <vector>
 
 #include "base/feature_list.h"
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
-#include "base/memory/weak_ptr.h"
+#include "base/memory/scoped_ptr.h"
 #include "base/observer_list.h"
+#include "base/synchronization/lock.h"
 #include "base/threading/thread_checker.h"
 
+namespace base {
+template <typename T>
+struct DefaultLazyInstanceTraits;
+}
+
 namespace metrics {
 
+namespace leak_detector {
+class LeakDetectorImpl;
+}
+
 // LeakDetector is an interface layer that connects the allocator
 // (base::allocator), the leak detector logic (LeakDetectorImpl), and any
 // external classes interested in receiving leak reports (extend the Observer
 // class).
 //
-// Currently it is stubbed out and only provides an interface for registering
-// observers to receive leak reports.
-// TODO(sque): Add the full functionality and allow only one instance.
+// Only one instance of this class can exist. Access this instance using
+// GetInstance(). Do not create an instance of this class directly.
 //
-// This class is not thread-safe, and it should always be called on the same
-// thread that instantiated it.
+// These member functions are thread-safe:
+// - AllocHook
+// - FreeHook
+// - AddObserver
+// - RemoveObserver
+//
+// All other functions must always be called from the same thread. This is
+// enforced with a DCHECK.
 class LeakDetector {
  public:
   // Contains a report of a detected memory leak.
   struct LeakReport {
     LeakReport();
     ~LeakReport();
 
     size_t alloc_size_bytes;
 
     // Unlike the CallStack struct, which consists of addresses, this call stack
     // will contain offsets in the executable binary.
     std::vector<uintptr_t> call_stack;
   };
 
   // Interface for receiving leak reports.
   class Observer {
    public:
     virtual ~Observer() {}
 
     // Called by leak detector to report a leak.
     virtual void OnLeakFound(const LeakReport& report) = 0;
   };
 
-  // Constructor arguments:
+  // Returns the sole instance, or creates it if it hasn't already been created.
+  static LeakDetector* GetInstance();
+
+  // Initializer arguments:
   // sampling_rate:
   //     Pseudorandomly sample a fraction of the incoming allocations and frees,
   //     based on hash values. Setting to 0 means no allocs/frees are sampled.
   //     Setting to 1.0 or more means all allocs/frees are sampled. Anything in
   //     between will result in an approximately that fraction of allocs/frees
   //     being sampled.
   // max_call_stack_unwind_depth:
   //     The max number of call stack frames to unwind.
   // analysis_interval_bytes:
   //     Perform a leak analysis each time this many bytes have been allocated
   //     since the previous analysis.
   // size_suspicion_threshold, call_stack_suspicion_threshold:
   //     A possible leak should be suspected this many times to take action on i
   //     For size analysis, the action is to start profiling by call stack.
   //     For call stack analysis, the action is to generate a leak report.
-  LeakDetector(float sampling_rate,
-               size_t max_call_stack_unwind_depth,
-               uint64_t analysis_interval_bytes,
-               uint32_t size_suspicion_threshold,
-               uint32_t call_stack_suspicion_threshold);
-
-  ~LeakDetector();
+  void Init(float sampling_rate,
+            size_t max_call_stack_unwind_depth,
+            uint64_t analysis_interval_bytes,
+            uint32_t size_suspicion_threshold,
+            uint32_t call_stack_suspicion_threshold);
 
   // Add |observer| to the list of stored Observers, i.e. |observers_|, to which
   // the leak detector will report leaks.
   void AddObserver(Observer* observer);
 
   // Remove |observer| from |observers_|.
   void RemoveObserver(Observer* observer);
 
  private:
+  friend base::DefaultLazyInstanceTraits<LeakDetector>;
   FRIEND_TEST_ALL_PREFIXES(LeakDetectorTest, NotifyObservers);
 
+  // Keep these private, as this class is meant to be initialized only through
+  // the lazy instance, and never destroyed.
+  LeakDetector();
+  ~LeakDetector();
+
+  // Allocator hook function that processes each alloc. Performs sampling and
+  // unwinds call stack if necessary. Passes the allocated memory |ptr| and
+  // allocation size |size| along with call stack info to RecordAlloc().
+  static void AllocHook(const void* ptr, size_t size);
+
+  // Allocator hook function that processes each free. Performs sampling and
+  // passes the allocation address |ptr| to |impl_|.
+  static void FreeHook(const void* ptr);
+
+  // Give an pointer |ptr|, computes a hash of the pointer value and compares it
+  // against |sampling_factor_| to determine if it should be sampled. This
+  // allows the same pointer to be sampled during both alloc and free.
+  bool ShouldSample(const void* ptr) const;
+
   // Notifies all Observers in |observers_| with the given vector of leak
   // reports.
   void NotifyObservers(const std::vector<LeakReport>& reports);
 
   // List of observers to notify when there's a leak report.
+  // TODO(sque): Consider using ObserverListThreadSafe instead.
   base::ObserverList<Observer> observers_;
 
+  // For atomic access to |observers_|.
+  base::Lock observers_lock_;
+
+  // Handles leak detection logic. Must be called under lock as LeakDetectorImpl
+  // uses shared resources.
+  scoped_ptr<leak_detector::LeakDetectorImpl> impl_;
+
   // For thread safety.
   base::ThreadChecker thread_checker_;
 
-  // For generating closures containing objects of this class.
-  base::WeakPtrFactory<LeakDetector> weak_factory_;
+  // Total number of bytes allocated, computed before sampling.
+  size_t total_alloc_size_;
+
+  // The value of |total_alloc_size_| the last time there was a leak analysis,
+  // rounded down to the nearest multiple of |analysis_interval_bytes_|.
+  size_t last_analysis_alloc_size_;
+
+  // For atomic access to |impl_|, |total_alloc_size_| and
+  // |last_analysis_alloc_size_|.
+  base::Lock recording_lock_;
+
+  // Perform a leak analysis each time this many bytes have been allocated since
+  // the previous analysis.
+  size_t analysis_interval_bytes_;
+
+  // When unwinding call stacks, unwind no more than this number of frames.
+  size_t max_call_stack_unwind_depth_;
+
+  // Sampling factor used by ShouldSample(). It's full range of values
+  // corresponds to the allowable range of |sampling_rate| passed in during
+  // initialization: [0.0f, 1.0f] -> [0, UINT64_MAX].
+  uint64_t sampling_factor_;
 
   DISALLOW_COPY_AND_ASSIGN(LeakDetector);
 };
 
 }  // namespace metrics
 
 #endif  // COMPONENTS_METRICS_LEAK_DETECTOR_LEAK_DETECTOR_H_