[jira] [Created] (LOGCXX-430) LogManager::getRootLogger is not thread-safe

["Thorsten Schöning (JIRA)" <lo...@logging.apache.org>]

Thorsten Schöning created LOGCXX-430:
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             Summary: LogManager::getRootLogger is not thread-safe
                 Key: LOGCXX-430
                 URL: https://issues.apache.org/jira/browse/LOGCXX-430
             Project: Log4cxx
          Issue Type: Bug
          Components: Core
    Affects Versions: 0.10.0
            Reporter: Thorsten Schöning


Kaspar Fischer reported following on the user mailing list:

> I am running into a situation where calling getRootLogger()
> concurrently from many requests results in a EXC_BAD_ACCESS:  

> liblog4cxx.10.dylib`log4cxx::LogManager::getRootLogger():
> 0x101f180a0:  pushq  %rbp  
> 0x101f180a1:  movq   %rsp, %rbp
> 0x101f180a4:  pushq  %rbx
> 0x101f180a5:  pushq  %rax
> 0x101f180a6:  movq   %rdi, %rbx
> 0x101f180a9:  callq  0x101f17de0               ;
> log4cxx::LogManager::getLoggerRepository()  
> 0x101f180ae:  movq   8(%rax), %rsi
> 0x101f180b2:  movq   (%rsi), %rax
> 0x101f180b5:  movq   %rbx, %rdi
> 0x101f180b8:  callq  *120(%rax) <<<<<< THREAD  1: EXC_BAD_ACCESS (code=EXC_I386_GPFLT)
> 0x101f180bb:  movq   %rbx, %rax
> 0x101f180be:  addq   $8, %rsp
> 0x101f180c2:  popq   %rbx
> 0x101f180c3:  popq   %rbp
> 0x101f180c4:  ret    
> 0x101f180c5:  nopw   %cs:(%rax,%rax)  

> If I replace the logging statement with a statement that writes to
> std::cerr, I do not run into any problems.  

> I am using log4cxx 0.10.0 on MacOS 10.9.1.

The call to getRootLogger ultimately results in:

> RepositorySelectorPtr& LogManager::getRepositorySelector() {
>    //
>    //     call to initialize APR and trigger "start" of logging clock
>    //
>    APRInitializer::initialize();
>    static spi::RepositorySelectorPtr selector;
>    return selector;
> }

It looks like we have the same problem here like in LOGCXX-394, a function static which is not thread-safe. Therefore we shoudl fix this like we did in LOGCXX-394 by removing the function static.

Problem is that for this to work we need to change the return type of the function, which shouldn't be a problem because it's private, but need to change additional functions as well: getLoggerRepository and setRepositorySelector both currently rely on the current behavior of getRepositorySelector.

Additionally what I don't understand is why APRInitializer is called more than once even if RepositorySelector only got created once because of it's static.

Looks ike we need to rework the whole part, maybe make it static on a class level like the guard.



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