Bluetooth: macOS: DidModifyServices can happens while scanning

device/bluetooth/bluetooth_remote_gatt_characteristic_mac.mm

 // 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.
 
 #include "device/bluetooth/bluetooth_remote_gatt_characteristic_mac.h"
 
 #include "base/bind.h"
 #include "base/memory/ptr_util.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/threading/thread_task_runner_handle.h"
@@ skipping 51 matching lines @@
     DCHECK(false);
     result |= BluetoothGattCharacteristic::PROPERTY_INDICATE;
   }
   return result;
 }
 }  // namespace
 
 BluetoothRemoteGattCharacteristicMac::BluetoothRemoteGattCharacteristicMac(
     BluetoothRemoteGattServiceMac* gatt_service,
     CBCharacteristic* cb_characteristic)
-    : gatt_service_(gatt_service),
+    : is_discovery_complete_(false),
+      discovery_pending_count_(0),
+      gatt_service_(gatt_service),
       cb_characteristic_(cb_characteristic, base::scoped_policy::RETAIN),
       characteristic_value_read_or_write_in_progress_(false) {
   uuid_ = BluetoothAdapterMac::BluetoothUUIDWithCBUUID(
       [cb_characteristic_.get() UUID]);
   identifier_ = base::SysNSStringToUTF8(
       [NSString stringWithFormat:@"%s-%p", uuid_.canonical_value().c_str(),
                                  (void*)cb_characteristic_]);
 }
 
 BluetoothRemoteGattCharacteristicMac::~BluetoothRemoteGattCharacteristicMac() {
@@ skipping 155 matching lines @@
   DCHECK(unsubscribe_from_notification_callbacks_.second.is_null());
   unsubscribe_from_notification_callbacks_ =
       std::make_pair(callback, error_callback);
   [GetCBPeripheral() setNotifyValue:NO
                   forCharacteristic:cb_characteristic_.get()];
 }
 
 void BluetoothRemoteGattCharacteristicMac::DiscoverDescriptors() {
   VLOG(1) << *this << ": Discover descriptors.";
   is_discovery_complete_ = false;
+  ++discovery_pending_count_;
   [GetCBPeripheral()
       discoverDescriptorsForCharacteristic:cb_characteristic_.get()];
 }
 
 void BluetoothRemoteGattCharacteristicMac::DidUpdateValue(NSError* error) {
   CHECK_EQ(GetCBPeripheral().state, CBPeripheralStateConnected);
   // This method is called when the characteristic is read and when a
   // notification is received.
   if (characteristic_value_read_or_write_in_progress_) {
     std::pair<ValueCallback, ErrorCallback> callbacks;
@@ skipping 81 matching lines @@
             << BluetoothAdapterMac::String(error)
             << ", error code: " << error_code;
     reentrant_safe_callbacks.second.Run(error_code);
     return;
   }
   reentrant_safe_callbacks.first.Run();
 }
 
 void BluetoothRemoteGattCharacteristicMac::DidDiscoverDescriptors() {
   DCHECK(!is_discovery_complete_);
+  DCHECK(discovery_pending_count_ > 0);
   VLOG(1) << *this << ": Did discover descriptors.";
+  --discovery_pending_count_;
   std::unordered_set<std::string> descriptor_identifier_to_remove;
   for (const auto& iter : gatt_descriptor_macs_) {
     descriptor_identifier_to_remove.insert(iter.first);
   }
 
   for (CBDescriptor* cb_descriptor in cb_characteristic_.get().descriptors) {
     BluetoothRemoteGattDescriptorMac* gatt_descriptor_mac =
         GetBluetoothRemoteGattDescriptorMac(cb_descriptor);
     if (gatt_descriptor_mac) {
       VLOG(1) << *gatt_descriptor_mac << ": Known descriptor.";
@@ skipping 12 matching lines @@
   }
 
   for (const std::string& identifier : descriptor_identifier_to_remove) {
     auto pair_to_remove = gatt_descriptor_macs_.find(identifier);
     std::unique_ptr<BluetoothRemoteGattDescriptorMac> descriptor_to_remove;
     VLOG(1) << *descriptor_to_remove << ": Removed descriptor.";
     pair_to_remove->second.swap(descriptor_to_remove);
     gatt_descriptor_macs_.erase(pair_to_remove);
     GetMacAdapter()->NotifyGattDescriptorRemoved(descriptor_to_remove.get());
   }
-  is_discovery_complete_ = true;
+  is_discovery_complete_ = discovery_pending_count_ == 0;
 }
 
 bool BluetoothRemoteGattCharacteristicMac::IsReadable() const {
   return GetProperties() & BluetoothGattCharacteristic::PROPERTY_READ;
 }
 
 bool BluetoothRemoteGattCharacteristicMac::IsWritable() const {
   BluetoothGattCharacteristic::Properties properties = GetProperties();
   return (properties & BluetoothGattCharacteristic::PROPERTY_WRITE) ||
          (properties & PROPERTY_WRITE_WITHOUT_RESPONSE);
@@ skipping 54 matching lines @@
   const BluetoothRemoteGattServiceMac* service_mac =
       static_cast<const BluetoothRemoteGattServiceMac*>(
           characteristic.GetService());
   return out << "<BluetoothRemoteGattCharacteristicMac "
              << characteristic.GetUUID().canonical_value() << "/"
              << &characteristic
              << ", service: " << service_mac->GetUUID().canonical_value() << "/"
              << service_mac << ">";
 }
 }  // namespace device.