[KDevPlatform] bae38ce: Use pthread directly for the foreground mutex, pot

[Milian Wolff]

Sorry David, but this is a no-go. Pthread is not cross-platform, and I still 
did not find a single reason for why this should be a QMutex bug. Why does 
that work for us in all other cases (and tons of other projects), but no here?

Really, instead of putting work-around over work-around, we should dissect 
this problem and find the *real* reason.

Doing guess-work won't help, and so far you only proposed that there *could* 
be a bug in QMutex, without

a) explaining where the bug occurs
b) reporting a bug to Nokia

I'm heavily opposed to this, imo you should start to write unit tests and try 
to reproduce the deadlock before adding more workarounds.

Bye

David Nolden, 01.12.2010:
> commit bae38ceb983f7c7b0b66ca475dbfa689ace8313e
> branch master
> Author: David Nolden <david.nolden.kde at art-master.de>
> Date:   Wed Dec 1 17:53:52 2010 +0100
> 
>     Use pthread directly for the foreground mutex, potentially trying to
> workaround a problem in the QMutex implementation which leads to a rare
> deadlock. BUG: 252659
> 
> diff --git a/interfaces/CMakeLists.txt b/interfaces/CMakeLists.txt
> index 4fd1ec4..d832c85 100644
> --- a/interfaces/CMakeLists.txt
> +++ b/interfaces/CMakeLists.txt
> @@ -49,7 +49,8 @@ target_link_libraries(kdevplatforminterfaces
>          ${KDE4_KTEXTEDITOR_LIBS}
>          ${KDE4_THREADWEAVER_LIBRARIES}
>          ${QT_QTDESIGNER_LIBRARY}
> -        ${KDE4_KROSSCORE_LIBS})
> +        ${KDE4_KROSSCORE_LIBS}
> +        rt)
>  target_link_libraries(kdevplatforminterfaces LINK_INTERFACE_LIBRARIES
>          ${KDE4_KPARTS_LIBS}
>          ${KDE4_KTEXTEDITOR_LIBS}
> diff --git a/interfaces/foregroundlock.cpp b/interfaces/foregroundlock.cpp
> index ada7db9..4e3a73d 100644
> --- a/interfaces/foregroundlock.cpp
> +++ b/interfaces/foregroundlock.cpp
> @@ -24,8 +24,65 @@
> 
>  using namespace KDevelop;
> 
> +#define USE_PTHREAD_MUTEX
> +
> +#ifdef USE_PTHREAD_MUTEX
> +
> +#include <pthread.h>
> +#include <time.h>
> +
> +
> +class SimplePThreadMutex {
> +public:
> +    SimplePThreadMutex() {
> +        m_mutex = PTHREAD_MUTEX_INITIALIZER;
> +        int result = pthread_mutex_init(&m_mutex, 0);
> +        Q_ASSERT(result == 0);
> +    }
> +    ~SimplePThreadMutex() {
> +        pthread_mutex_destroy(&m_mutex);
> +    }
> +    void lock() {
> +        int result = pthread_mutex_lock(&m_mutex);
> +        Q_ASSERT(result == 0);
> +    }
> +    void unlock() {
> +        int result = pthread_mutex_unlock(&m_mutex);
> +        Q_ASSERT(result == 0);
> +    }
> +    bool tryLock(int interval) {
> +        if(interval == 0)
> +        {
> +            int result = pthread_mutex_trylock(&m_mutex);
> +            return result == 0;
> +        }else{
> +            timespec abs_time;
> +            clock_gettime(CLOCK_REALTIME, &abs_time);
> +            abs_time.tv_nsec += interval * 1000000;
> +            if(abs_time.tv_nsec >= 1000000000)
> +            {
> +                abs_time.tv_nsec -= 1000000000;
> +                abs_time.tv_sec += 1;
> +            }
> +
> +            int result = pthread_mutex_timedlock(&m_mutex, &abs_time);
> +            return result == 0;
> +        }
> +    }
> +
> +private:
> +    pthread_mutex_t m_mutex;
> +};
> +
>  namespace {
> +
> +SimplePThreadMutex internalMutex;
> +#else
> +
> +namespace {
> +
>  QMutex internalMutex;
> +#endif
>  QMutex tryLockMutex;
>  QMutex waitMutex;
>  QMutex finishMutex;


-- 
Milian Wolff
mail at milianw.de
http://milianw.de
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