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Code Issues Projects Releases Wiki Activity

Improved encapsulation of thread synchronisation as follows

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- replaced use of Object instance mutex with a private final Lock object
- replaced Object signaling with specific condition signalling
This commit is contained in:
Abraham Kiggundu
2014-12-23 23:55:56 +03:00
parent 276dcb1038
commit b074978472
19 changed files with 1001 additions and 478 deletions
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104
briar-desktop/src/org/briarproject/plugins/modem/ModemImpl.java
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@@ -10,6 +10,10 @@ import java.io.InputStream;
import java.io.OutputStream;
import java.util.concurrent.Executor;
import java.util.concurrent.Semaphore;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import java.util.logging.Logger;
import jssc.SerialPortEvent;
@@ -44,6 +48,11 @@ class ModemImpl implements Modem, WriteHandler, SerialPortEventListener {
private ReliabilityLayer reliability = null; // Locking: this
private boolean initialised = false, connected = false; // Locking: this
private final Lock synchLock = new ReentrantLock();
private final Condition connectedStateChanged = synchLock.newCondition();
private final Condition initialisedStateChanged = synchLock.newCondition();
ModemImpl(Executor executor, ReliabilityLayerFactory reliabilityFactory,
Clock clock, Callback callback, SerialPort port) {
@@ -91,14 +100,18 @@ class ModemImpl implements Modem, WriteHandler, SerialPortEventListener {
// Wait for the event thread to receive "OK"
boolean success = false;
try {
synchronized(this) {
synchLock.lock();
try {
long now = clock.currentTimeMillis();
long end = now + OK_TIMEOUT;
while(now < end && !initialised) {
wait(end - now);
initialisedStateChanged.await(end - now, TimeUnit.MILLISECONDS);
now = clock.currentTimeMillis();
}
success = initialised;
}
finally{
synchLock.unlock();
}
} catch(InterruptedException e) {
tryToClose(port);
@@ -123,11 +136,16 @@ class ModemImpl implements Modem, WriteHandler, SerialPortEventListener {
public void stop() throws IOException {
LOG.info("Stopping");
// Wake any threads that are waiting to connect
synchronized(this) {
synchLock.lock();
try {
// Wake any threads that are waiting to connect
initialised = false;
connected = false;
notifyAll();
initialisedStateChanged.signalAll();
connectedStateChanged.signalAll();
}
finally{
synchLock.unlock();
}
// Hang up if necessary and close the port
try {
@@ -148,7 +166,8 @@ class ModemImpl implements Modem, WriteHandler, SerialPortEventListener {
// Locking: stateChange
private void hangUpInner() throws IOException {
ReliabilityLayer reliability;
synchronized(this) {
synchLock.lock();
try {
if(this.reliability == null) {
LOG.info("Not hanging up - already on the hook");
return;
@@ -156,6 +175,9 @@ class ModemImpl implements Modem, WriteHandler, SerialPortEventListener {
reliability = this.reliability;
this.reliability = null;
connected = false;
}
finally{
synchLock.unlock();
}
reliability.stop();
LOG.info("Hanging up");
@@ -182,7 +204,8 @@ class ModemImpl implements Modem, WriteHandler, SerialPortEventListener {
try {
ReliabilityLayer reliability =
reliabilityFactory.createReliabilityLayer(this);
synchronized(this) {
synchLock.lock();
try {
if(!initialised) {
LOG.info("Not dialling - modem not initialised");
return false;
@@ -192,6 +215,9 @@ class ModemImpl implements Modem, WriteHandler, SerialPortEventListener {
return false;
}
this.reliability = reliability;
}
finally{
synchLock.unlock();
}
reliability.start();
LOG.info("Dialling");
@@ -204,14 +230,18 @@ class ModemImpl implements Modem, WriteHandler, SerialPortEventListener {
}
// Wait for the event thread to receive "CONNECT"
try {
synchronized(this) {
synchLock.lock();
try {
long now = clock.currentTimeMillis();
long end = now + CONNECT_TIMEOUT;
while(now < end && initialised && !connected) {
wait(end - now);
connectedStateChanged.await(end - now, TimeUnit.MILLISECONDS);
now = clock.currentTimeMillis();
}
if(connected) return true;
}
finally{
synchLock.unlock();
}
} catch(InterruptedException e) {
tryToClose(port);
@@ -227,8 +257,12 @@ class ModemImpl implements Modem, WriteHandler, SerialPortEventListener {
public InputStream getInputStream() throws IOException {
ReliabilityLayer reliability;
synchronized(this) {
synchLock.lock();
try {
reliability = this.reliability;
}
finally{
synchLock.unlock();
}
if(reliability == null) throw new IOException("Not connected");
return reliability.getInputStream();
@@ -236,8 +270,12 @@ class ModemImpl implements Modem, WriteHandler, SerialPortEventListener {
public OutputStream getOutputStream() throws IOException {
ReliabilityLayer reliability;
synchronized(this) {
synchLock.lock();
try {
reliability = this.reliability;
}
finally{
synchLock.unlock();
}
if(reliability == null) throw new IOException("Not connected");
return reliability.getOutputStream();
@@ -288,8 +326,12 @@ class ModemImpl implements Modem, WriteHandler, SerialPortEventListener {
private boolean handleData(byte[] b) throws IOException {
ReliabilityLayer reliability;
synchronized(this) {
synchLock.lock();
try {
reliability = this.reliability;
}
finally{
synchLock.unlock();
}
if(reliability == null) return false;
reliability.handleRead(b);
@@ -309,9 +351,13 @@ class ModemImpl implements Modem, WriteHandler, SerialPortEventListener {
lineLen = 0;
if(LOG.isLoggable(INFO)) LOG.info("Modem status: " + s);
if(s.startsWith("CONNECT")) {
synchronized(this) {
synchLock.lock();
try {
connected = true;
notifyAll();
connectedStateChanged.signalAll();
}
finally{
synchLock.unlock();
}
// There might be data in the buffer as well as text
int off = i + 1;
@@ -323,14 +369,22 @@ class ModemImpl implements Modem, WriteHandler, SerialPortEventListener {
return;
} else if(s.equals("BUSY") || s.equals("NO DIALTONE")
|| s.equals("NO CARRIER")) {
synchronized(this) {
synchLock.lock();
try {
connected = false;
notifyAll();
connectedStateChanged.signalAll();
}
finally{
synchLock.unlock();
}
} else if(s.equals("OK")) {
synchronized(this) {
synchLock.lock();
try {
initialised = true;
notifyAll();
initialisedStateChanged.signalAll();
}
finally{
synchLock.unlock();
}
} else if(s.equals("RING")) {
executor.execute(new Runnable() {
@@ -358,7 +412,8 @@ class ModemImpl implements Modem, WriteHandler, SerialPortEventListener {
try {
ReliabilityLayer reliability =
reliabilityFactory.createReliabilityLayer(this);
synchronized(this) {
synchLock.lock();
try {
if(!initialised) {
LOG.info("Not answering - modem not initialised");
return;
@@ -368,6 +423,9 @@ class ModemImpl implements Modem, WriteHandler, SerialPortEventListener {
return;
}
this.reliability = reliability;
}
finally{
synchLock.unlock();
}
reliability.start();
LOG.info("Answering");
@@ -380,14 +438,18 @@ class ModemImpl implements Modem, WriteHandler, SerialPortEventListener {
// Wait for the event thread to receive "CONNECT"
boolean success = false;
try {
synchronized(this) {
synchLock.lock();
try {
long now = clock.currentTimeMillis();
long end = now + CONNECT_TIMEOUT;
while(now < end && initialised && !connected) {
wait(end - now);
connectedStateChanged.await(end - now, TimeUnit.MILLISECONDS);
now = clock.currentTimeMillis();
}
success = connected;
}
finally{
synchLock.unlock();
}
} catch(InterruptedException e) {
tryToClose(port);