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Editorial Team
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Asked: 2026-06-11T09:00:47+00:00

Update 3 recently, I noticed that my code randomly causes Segmentation Fault errors. But

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Update 3

recently, I noticed that my code randomly causes Segmentation Fault errors. But I think that my code is pretty simple so far and I cant figure out where that error comes from. Since it happens randomly, I assume that there is some kind of race-condition. I think this is all the code that might be relevant, tell me if you need more:

namespace thread {
    pthread_t terminated_thread_id, /* and others */;
    pthread_mutex_t terminate_thread = PTHREAD_MUTEX_INITIALIZER;
    pthread_cond_t terminate_thread_signal = PTHREAD_COND_INITIALIZER;
    int total_thread_count = 0;
    int termination; // + sembufs

    inline void* Exit(void* value) {
    //  This must be unlocked after all join-related jobs are done
        semop(thread::termination, thread::termination_in_process, 2)
            pthread_mutex_lock(&thread::terminate_thread);
                thread::terminated_thread_id = pthread_self();
                pthread_cond_signal(&thread::terminate_thread_signal);
            pthread_mutex_unlock(&thread::terminate_thread);

        pthread_exit(value);
        return value;
    }
}
int main(int argc, const char** argv){
...
    pthread_mutex_lock(&thread::terminate_thread);
    if(0 != pthread_create(&thread::communication_handler_thread_id, NULL,    \
                           CommunicationHandler, NULL)){
        global::PrintDebug("pthread_create() failed", __FILE__, __LINE__);
    }
    /** 2 more pthread_create()-calls */       
    do{
        thread::terminated_thread_id = pthread_self();
        pthread_cond_wait(&thread::terminate_thread_signal,                   \
                          &thread::terminate_thread);
        if(!pthread_equal(thread::terminated_thread_id, pthread_self())){
            pthread_join(thread::terminated_thread_id, NULL);
    ...
            semop(thread::termination, thread::termination_done, 1)
        }
    }while(thread::total_thread_count > 0);

    pthread_mutex_unlock(&thread::terminate_thread);
    return 0;
}

The signal terminate_thread_signal is only emitted in the thread::Exit() function. That function is also only called at the end of the function that is used to create the thread.

This is what the debugger shows for the Call Stack:

#0 (    0xb7fe2424 in __kernel_vsyscall() (??:??)
#1 0xb7fbdfcf   __pthread_cond_wait(cond=0x80539c0, mutex=0x8053998) (pthread_cond_wait.c:153)
#2 0x804a094    main(argc=1, argv=0xbffff9c4) (/home/papergay/SeekYourCar/0.2/Server/main.cpp:121)

What I already know is, if the error happens, then no thread has called thread::Exit() yet.
I am also using an unnamed namespace with a few initializations (if that might be relevant).
I am using Code::Blocks as IDE and GCC as compiler.

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1 Answer

  1. Editorial Team

    This is quite late, but I forgot to post it for future references.
    This is how I fixed it:

    I upgraded my GCC compiler from version to 4.5.X to version 4.7.X as well as my kernel from 2.6.X to 3.2.X and fixed some errors regarding the global instanciating of a class and a static member variable by providing an explicit constructor in order to allow a global declaration without initialization.
    But I think that upgrading the GCC compiler is all what was needed.

    Looks like the implementation of the function was not proper. Or there were some errors in the kernel code?

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