cuttlefish::ScreenConnectorCtrl Class Reference

#include <screen_connector_ctrl.h>

Collaboration diagram for cuttlefish::ScreenConnectorCtrl:

Public Types
enum class	ModeType { kAndroidMode , kConfUI_Mode }

Public Member Functions
	ScreenConnectorCtrl ()
void	WaitAndroidMode ()
void	SetMode (const ModeType mode)
auto	GetMode ()
void	SemWait ()
void	SemPost ()

Private Attributes
std::mutex	mode_mtx_
std::condition_variable	and_mode_cv_
std::atomic< ModeType >	atomic_mode_
Semaphore	sem_

Detailed Description

mechanism to orchestrate concurrent executions of threads that work for screen connector

One thing is when any of wayland/socket-based connector or confirmation UI has a frame, it should wake up the consumer The two queues are separate, so the conditional variables, etc, can't be in the queue

Member Enumeration Documentation

ModeType

enum class cuttlefish::ScreenConnectorCtrl::ModeType

strong

Enumerator
kAndroidMode
kConfUI_Mode

Constructor & Destructor Documentation

ScreenConnectorCtrl()

cuttlefish::ScreenConnectorCtrl::ScreenConnectorCtrl ( )

inline

Member Function Documentation

GetMode()

auto cuttlefish::ScreenConnectorCtrl::GetMode ( )

inline

SemPost()

void cuttlefish::ScreenConnectorCtrl::SemPost ( )

inline

SemWait()

void cuttlefish::ScreenConnectorCtrl::SemWait ( )

inline

SetMode()

void cuttlefish::ScreenConnectorCtrl::SetMode ( const ModeType  mode )

inline

WaitAndroidMode()

void cuttlefish::ScreenConnectorCtrl::WaitAndroidMode ( )

inline

The thread that enqueues Android frames will call this to wait until the mode is kAndroidMode

Logically, using atomic_mode_ alone is not sufficient. Using mutex alone is logically complete but slow.

Note that most of the time, the mode is kAndroidMode. Also, note that this method is called at every single frame.

As an optimization, we check atomic_mode_ first. If failed, we wait for kAndroidMode with mutex-based lock

The actual synchronization is not at the and_mode_cv_.wait line but at this line: if (atomic_mode_ == ModeType::kAndroidMode) {

This trick reduces the flag checking delays by 70+% on a Gentoo based amd64 desktop, with Linux 5.10

Member Data Documentation

and_mode_cv_

std::condition_variable cuttlefish::ScreenConnectorCtrl::and_mode_cv_

private

atomic_mode_

std::atomic<ModeType> cuttlefish::ScreenConnectorCtrl::atomic_mode_

private

mode_mtx_

std::mutex cuttlefish::ScreenConnectorCtrl::mode_mtx_

private

sem_

Semaphore cuttlefish::ScreenConnectorCtrl::sem_

private

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The documentation for this class was generated from the following file:

• cuttlefish/host/libs/screen_connector/screen_connector_ctrl.h