Logging may cause deadlock.
---------------------------
Key: SSHD-152
URL: https://issues.apache.org/jira/browse/SSHD-152
Project: MINA SSHD
Issue Type: Bug
Affects Versions: 0.5.0
Reporter: Gunnar Wagenknecht
I'm not really sure what I did but I think I somehow managed to deadlock my
system using SSHD in combination with Logback console appender.
Thread 1
{noformat}
Thread [Thread-21] (Suspended)
owns: ChannelOutputStream (id=481)
owns: ConsoleOutputStream (id=482)
owns: PrintStream (id=483)
owns: Object (id=202)
waited by: Thread [...] (Suspended)
waited by: Thread [...] (Suspended)
waited by: Thread [...] (Suspended)
waited by: Thread [NioProcessor-2] (Suspended)
waited by: Thread [...] (Suspended)
waited by: Thread [...] (Suspended)
waited by: Thread [...] (Suspended)
waited by: Thread [...] (Suspended)
waited by: Thread [...] (Suspended)
waited by: Thread [...] (Suspended)
owns: OutputStreamWriter (id=484)
waiting for: Window (id=485)
Object.wait(long) line: not available [native method]
Window(Object).wait() line: 503
Window.waitForSpace() line: 146
ChannelOutputStream.flush() line: 104
ConsoleOutputStream.flush() line: 97
ConsoleOutputStream.write(int) line: 83
ConsoleOutputStream(OutputStream).write(byte[], int, int) line: 116
PrintStream.write(byte[], int, int) line: 480
PrintStream(FilterOutputStream).write(byte[]) line: 97
ThreadPrintStream.write(byte[]) line: 245
ConsoleTarget$1.write(byte[]) line: 36
PatternLayoutEncoder(LayoutWrappingEncoder<E>).doEncode(E) line: 103
ConsoleAppender<E>(OutputStreamAppender<E>).writeOut(E) line: 193
ConsoleAppender<E>(OutputStreamAppender<E>).subAppend(E) line: 217
ConsoleAppender<E>(OutputStreamAppender<E>).append(E) line: 108
ConsoleAppender<E>(UnsynchronizedAppenderBase<E>).doAppend(E) line: 88
AppenderAttachableImpl<E>.appendLoopOnAppenders(E) line: 64
Logger.appendLoopOnAppenders(ILoggingEvent) line: 285
Logger.callAppenders(ILoggingEvent) line: 272
Logger.buildLoggingEventAndAppend(String, Marker, Level, String,
Object[], Throwable) line: 473
Logger.filterAndLog_2(String, Marker, Level, String, Object, Object,
Throwable) line: 464
Logger.debug(String, Object, Object) line: 542
ChannelOutputStream.flush() line: 119
...
{noformat}
Thread 2
{noformat}
Thread [NioProcessor-2] (Suspended)
owns: Object (id=150)
waiting for: Object (id=202)
owned by: Thread [Thread-21] (Suspended)
waiting for: Window (id=485)
ConsoleAppender<E>(OutputStreamAppender<E>).subAppend(E) line: 217
ConsoleAppender<E>(OutputStreamAppender<E>).append(E) line: 108
ConsoleAppender<E>(UnsynchronizedAppenderBase<E>).doAppend(E) line: 88
AppenderAttachableImpl<E>.appendLoopOnAppenders(E) line: 64
Logger.appendLoopOnAppenders(ILoggingEvent) line: 285
Logger.callAppenders(ILoggingEvent) line: 272
Logger.buildLoggingEventAndAppend(String, Marker, Level, String,
Object[], Throwable) line: 473
Logger.filterAndLog_1(String, Marker, Level, String, Object, Throwable)
line: 445
Logger.debug(String, Object) line: 538
ServerSession.handleMessage(Buffer) line: 119
...
{noformat}
I think that one thread is waiting for Window to expand. The SSHD logger has a
console appender. Unfortunately, the wait happends within a write by console
appender. Thus all other threads that also log to the console will block
because they wait for the Logback console appender lock.
I think that a Logback console appender should not write to the SSHD console by
default. Can this be disabled somehow?
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