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https://issues.apache.org/jira/browse/LOGCXX-537?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17457772#comment-17457772
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Robert Middleton commented on LOGCXX-537:
-----------------------------------------
Future reference for me: ISOCPP guidelines recommend using a [recursive
mutex|http://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#cp22-never-call-unknown-code-while-holding-a-lock-eg-a-callback]
if you're calling unknown code(e.g. callback).
Since that is basically what is happening here, maybe the recursive mutex is
not a bad idea. I need to think about this a little bit - it may make sense to
make things have recursive mutexes as they did before, but that may wait until
the next major version(since there are probably a number of locations where
this would be useful).
> 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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