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Ref-counted rewrite of ChannelManager.

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The complexity of the last ChannelManager and potentially usage of it as well caused race conditions and deadlocks in loopback voe_auto_test. This ref-counted solution takes no long-term locks, uses less locks overall and is significantly easier to understand.

ScopedChannel has been split up into a ChannelOwner with a reference to a channel and an Iterator over ChannelManager. Previous code was really used for both things. ChannelOwner is used as a shared pointer to a channel object, while an Iterator should work as expected.

BUG=2081
R=tommi@webrtc.org, xians@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/1802004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@4502 4adac7df-926f-26a2-2b94-8c16560cd09d
This commit is contained in:
pbos@webrtc.org
2013-08-07 17:57:36 +00:00
parent 825e9b0a9b
commit 676ff1ed89
28 changed files with 581 additions and 1072 deletions
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139
webrtc/voice_engine/channel_manager.h
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@ -11,79 +11,108 @@
#ifndef WEBRTC_VOICE_ENGINE_CHANNEL_MANAGER_H
#define WEBRTC_VOICE_ENGINE_CHANNEL_MANAGER_H
#include <vector>
#include "webrtc/system_wrappers/interface/atomic32.h"
#include "webrtc/system_wrappers/interface/constructor_magic.h"
#include "webrtc/system_wrappers/interface/critical_section_wrapper.h"
#include "webrtc/system_wrappers/interface/scoped_ptr.h"
#include "webrtc/typedefs.h"
#include "webrtc/voice_engine/channel_manager_base.h"
namespace webrtc
{
namespace webrtc {
namespace voe {
namespace voe
{
class ScopedChannel;
class Channel;
class ChannelManager: private ChannelManagerBase
{
friend class ScopedChannel;
// Shared-pointer implementation for keeping track of Channels. The underlying
// shared instance will be dropped when no more ChannelOwners point to it.
//
// One common source of ChannelOwner instances are
// ChannelManager::CreateChannel() and ChannelManager::GetChannel(...).
// It has a similar use case to shared_ptr in C++11. Should this move to C++11
// in the future, this class should be replaced by exactly that.
//
// To access the underlying Channel, use .channel().
// IsValid() implements a convenience method as an alternative for checking
// whether the underlying pointer is NULL or not.
//
// Channel channel_owner = channel_manager.GetChannel(channel_id);
// if (channel_owner.IsValid())
// channel_owner.channel()->...;
//
class ChannelOwner {
public:
explicit ChannelOwner(Channel* channel);
ChannelOwner(const ChannelOwner& channel_owner);
public:
bool CreateChannel(int32_t& channelId);
~ChannelOwner();
int32_t DestroyChannel(int32_t channelId);
ChannelOwner& operator=(const ChannelOwner& other);
int32_t MaxNumOfChannels() const;
Channel* channel() { return channel_ref_->channel.get(); }
bool IsValid() { return channel_ref_->channel.get() != NULL; }
private:
// Shared instance of a Channel. Copying ChannelOwners increase the reference
// count and destroying ChannelOwners decrease references. Channels are
// deleted when no references to them are held.
struct ChannelRef {
ChannelRef(Channel* channel);
const scoped_ptr<Channel> channel;
Atomic32 ref_count;
};
int32_t NumOfChannels() const;
void GetChannelIds(int32_t* channelsArray,
int32_t& numOfChannels) const;
ChannelManager(uint32_t instanceId);
~ChannelManager();
private:
ChannelManager(const ChannelManager&);
ChannelManager& operator=(const ChannelManager&);
Channel* GetChannel(int32_t channelId) const;
void GetChannels(MapWrapper& channels) const;
void ReleaseChannel();
virtual void* NewItem(int32_t itemID);
virtual void DeleteItem(void* item);
uint32_t _instanceId;
ChannelRef* channel_ref_;
};
class ScopedChannel
{
public:
// Can only be created by the channel manager
ScopedChannel(ChannelManager& chManager);
class ChannelManager {
public:
ChannelManager(uint32_t instance_id);
ScopedChannel(ChannelManager& chManager, int32_t channelId);
// Upon construction of an Iterator it will grab a copy of the channel list of
// the ChannelManager. The iteration will then occur over this state, not the
// current one of the ChannelManager. As the Iterator holds its own references
// to the Channels, they will remain valid even if they are removed from the
// ChannelManager.
class Iterator {
public:
explicit Iterator(ChannelManager* channel_manager);
Channel* ChannelPtr();
Channel* GetChannel();
bool IsValid();
Channel* GetFirstChannel(void*& iterator) const;
void Increment();
Channel* GetNextChannel(void*& iterator) const;
private:
size_t iterator_pos_;
std::vector<ChannelOwner> channels_;
~ScopedChannel();
private:
ChannelManager& _chManager;
Channel* _channelPtr;
MapWrapper _channels;
DISALLOW_COPY_AND_ASSIGN(Iterator);
};
// CreateChannel will always return a valid ChannelOwner instance.
ChannelOwner CreateChannel();
// ChannelOwner.channel() will be NULL if channel_id is invalid or no longer
// exists. This should be checked with ChannelOwner::IsValid().
ChannelOwner GetChannel(int32_t channel_id);
void GetAllChannels(std::vector<ChannelOwner>* channels);
void DestroyChannel(int32_t channel_id);
void DestroyAllChannels();
size_t NumOfChannels() const;
private:
uint32_t instance_id_;
Atomic32 last_channel_id_;
scoped_ptr<CriticalSectionWrapper> lock_;
std::vector<ChannelOwner> channels_;
DISALLOW_COPY_AND_ASSIGN(ChannelManager);
};
} // namespace voe
} // namespace webrtc
#endif // WEBRTC_VOICE_ENGINE_CHANNEL_MANAGER_H