This is an automated email from the ASF dual-hosted git repository.
twolf pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/mina-sshd.git
The following commit(s) were added to refs/heads/master by this push:
new 5a9194bb9 Replace "synchronized" blocks in AbstractSession with
ReentrantLock
5a9194bb9 is described below
commit 5a9194bb9bc86384d5303dcb6bd41c6f67ce9a42
Author: Evgenii Pasynkov <[email protected]>
AuthorDate: Fri Dec 12 18:12:04 2025 +0100
Replace "synchronized" blocks in AbstractSession with ReentrantLock
synchronized blocks pin the virtual thread under JDK21+ to physical thread.
It is better to avoid such pinning in I/O bound operations so VirtualThread
planner can do its job
---
.../sshd/common/session/helpers/AbstractSession.java | 20 +++++++++++++++-----
.../sshd/server/session/AbstractServerSession.java | 5 ++++-
2 files changed, 19 insertions(+), 6 deletions(-)
diff --git
a/sshd-core/src/main/java/org/apache/sshd/common/session/helpers/AbstractSession.java
b/sshd-core/src/main/java/org/apache/sshd/common/session/helpers/AbstractSession.java
index 029808107..fd8784c4e 100644
---
a/sshd-core/src/main/java/org/apache/sshd/common/session/helpers/AbstractSession.java
+++
b/sshd-core/src/main/java/org/apache/sshd/common/session/helpers/AbstractSession.java
@@ -47,6 +47,7 @@ import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.atomic.AtomicReference;
+import java.util.concurrent.locks.ReentrantLock;
import java.util.function.LongConsumer;
import java.util.logging.Level;
import java.util.stream.Collectors;
@@ -196,8 +197,8 @@ public abstract class AbstractSession extends SessionHelper
{
protected int decoderState;
protected int decoderLength;
protected SshException discarding;
- protected final Object encodeLock = new Object();
- protected final Object decodeLock = new Object();
+ protected final ReentrantLock encodeLock = new ReentrantLock();
+ protected final ReentrantLock decodeLock = new ReentrantLock();
protected final Object requestLock = new Object();
/**
@@ -501,7 +502,8 @@ public abstract class AbstractSession extends SessionHelper
{
* @throws Exception if an error occurs while decoding or handling the data
*/
public void messageReceived(Readable buffer) throws Exception {
- synchronized (decodeLock) {
+ decodeLock.lock();
+ try {
decoderBuffer.putBuffer(buffer);
// One of those properties will be set by the constructor and the
other
// one should be set by the readIdentification method
@@ -513,6 +515,8 @@ public abstract class AbstractSession extends SessionHelper
{
}
}
decode();
+ } finally {
+ decodeLock.unlock();
}
}
@@ -718,13 +722,16 @@ public abstract class AbstractSession extends
SessionHelper {
prepareNewKeys();
Buffer buffer = createBuffer(SshConstants.SSH_MSG_NEWKEYS, Byte.SIZE);
IoWriteFuture future;
- synchronized (encodeLock) {
+ encodeLock.lock();
+ try {
// writePacket() would also work since it would never try to queue
the packet, and would never try to
// initiate a new KEX, and thus would never try to get the kexLock
monitor. If it did, we might get a
// deadlock due to lock inversion. It seems safer to push this out
directly, though.
future = doWritePacket(buffer);
// Use the new settings from now on for any outgoing packet
setOutputEncoding();
+ } finally {
+ encodeLock.unlock();
}
kexHandler.updateState(() -> kexState.set(KexState.KEYS));
@@ -1169,11 +1176,14 @@ public abstract class AbstractSession extends
SessionHelper {
// Synchronize all write requests as needed by the encoding algorithm
// and also queue the write request in this synchronized block to
ensure
// packets are sent in the correct order
- synchronized (encodeLock) {
+ encodeLock.lock();
+ try {
Buffer packet = resolveOutputPacket(buffer);
IoSession networkSession = getIoSession();
IoWriteFuture future = networkSession.writeBuffer(packet);
return future;
+ } finally {
+ encodeLock.unlock();
}
}
diff --git
a/sshd-core/src/main/java/org/apache/sshd/server/session/AbstractServerSession.java
b/sshd-core/src/main/java/org/apache/sshd/server/session/AbstractServerSession.java
index 25108ce7e..54c465ebb 100644
---
a/sshd-core/src/main/java/org/apache/sshd/server/session/AbstractServerSession.java
+++
b/sshd-core/src/main/java/org/apache/sshd/server/session/AbstractServerSession.java
@@ -317,7 +317,8 @@ public abstract class AbstractServerSession extends
AbstractSession implements S
Buffer response = createBuffer(SshConstants.SSH_MSG_USERAUTH_SUCCESS,
Byte.SIZE);
IoWriteFuture future;
IoSession networkSession = getIoSession();
- synchronized (encodeLock) {
+ encodeLock.lock();
+ try {
Buffer packet = resolveOutputPacket(response);
setUsername(username);
@@ -327,6 +328,8 @@ public abstract class AbstractServerSession extends
AbstractSession implements S
// Now we can inform the peer that authentication is successful
future = networkSession.writeBuffer(packet);
+ } finally {
+ encodeLock.unlock();
}
resetIdleTimeout();
