[jira] [Comment Edited] (LOGCXX-537) double mutex lock

["Truman Lackey (Jira)" <lo...@logging.apache.org>]

    [ https://issues.apache.org/jira/browse/LOGCXX-537?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17458533#comment-17458533 ] 

Truman Lackey edited comment on LOGCXX-537 at 12/13/21, 4:59 PM:
-----------------------------------------------------------------

[~rmiddleton] Couple of other things I noticed.

In SocketAppenderSkeleton::monitor() there is a thread::sleep_for and an interrupt.wait_for both have the recconnectDelay argument passed in. This is causing the reconnect time to double.

in SocketAppenderSkeleton::close()
{code:c++}
std::unique_lock<std::mutex> lock2(interrupt_mutex);
interrupt.notify_all();
{code}
Is the lock needed?

When I test against the  [LOGCXX-537 |https://github.com/apache/logging-log4cxx/tree/LOGCXX-537] branch if I kill the receiver and start it up again messages are not be received.

Changing void SocketAppenderSkeleton::fireConnectorInternal() to the following fixes this:

{code:c++}
void SocketAppenderSkeleton::fireConnectorInternal(){
	if ( !thread.joinable() )
	{
		LogLog::debug(LOG4CXX_STR("Connector thread not alive: starting monitor."));

		thread = ThreadUtility::instance()->createThread( LOG4CXX_STR("SocketAppend"), &SocketAppenderSkeleton::monitor, this );
	}
	else {
		interrupt.notify_all();
		thread.join();
		thread = ThreadUtility::instance()->createThread( LOG4CXX_STR("SocketAppend"), &SocketAppenderSkeleton::monitor, this );
	}
}
{code}


was (Author: JIRAUSER281485):
[~rmiddleton] Couple of other things I noticed.

In SocketAppenderSkeleton::monitor() there is a thread::sleep_for and an interrupt.wait_for both have the recconnectDelay argument passed in. This is causing the reconnect time to double.

in SocketAppenderSkeleton::close()

		std::unique_lock<std::mutex> lock2(interrupt_mutex);
		interrupt.notify_all();

Is the lock needed?

When I test against the  [LOGCXX-537 |https://github.com/apache/logging-log4cxx/tree/LOGCXX-537] branch if I kill the receiver and start it up again messages are not be received.

> double mutex lock
> -----------------
>
>                 Key: LOGCXX-537
>                 URL: https://issues.apache.org/jira/browse/LOGCXX-537
>             Project: Log4cxx
>          Issue Type: Bug
>          Components: Appender
>    Affects Versions: 0.12.1
>         Environment: Ubuntu 18.04
>            Reporter: Truman Lackey
>            Priority: Major
>             Fix For: 0.13.0
>
>
> There is a possibility of the SocketAppender calling std::unique_lock<log4cxx::shared_mutex> lock(mutex) twice causing a deadlock exception. In socketappenderskeleton.cpp connect call if the exception is caught on line 118 then fireConnector() will be called.  On line 160 the mutex is attempted to be locked again but it has already been locked in the appendersleketo.cpp doAppend call. This causes log4cxx to throw a  std::err::resource_deadlock_would_occur



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