EGL: deallocate TLS data on thread termination

void egl_tls_t::validateTLSKey()

{

    struct TlsKeyInitializer {

        static void create() {

            pthread_key_create(&sKey, (void (*)(void*))&eglReleaseThread);

        }

        static void create() { pthread_key_create(&sKey, destructTLSData); }

    };

    pthread_once(&sOnceKey, TlsKeyInitializer::create);

}

void egl_tls_t::destructTLSData(void* data) {

    egl_tls_t* tls = static_cast<egl_tls_t*>(data);

    if (!tls) return;

    // Several things in the call tree of eglReleaseThread expect to be able to get the current

    // thread state directly from TLS. That's a problem because Bionic has already cleared our

    // TLS pointer before calling this function (pthread_getspecific(sKey) will return nullptr).

    // Instead the data is passed as our parameter.

    //

    // Ideally we'd refactor this so we have thin wrappers that retrieve thread state from TLS and

    // then pass it as a parameter (or 'this' pointer) to functions that do the real work without

    // touching TLS. Then from here we could just call those implementation functions with the the

    // TLS data we just received as a parameter.

    //

    // But that's a fairly invasive refactoring, so to do this robustly in the short term we just

    // put the data *back* in TLS and call the top-level eglReleaseThread. It and it's call tree

    // will retrieve the value from TLS, and then finally clear the TLS data. Bionic explicitly

    // tolerates re-setting the value that it's currently trying to destruct (see

    // pthread_key_clean_all()). Even if we forgot to clear the restored TLS data, bionic would

    // call the destructor again, but eventually gives up and just leaks the data rather than

    // enter an infinite loop.

    pthread_setspecific(sKey, tls);

    eglReleaseThread();

    ALOGE_IF(pthread_getspecific(sKey) != nullptr,

             "EGL TLS data still exists after eglReleaseThread");

}

void egl_tls_t::setErrorEtcImpl(

        const char* caller, int line, EGLint error, bool quiet) {

    validateTLSKey();

    egl_tls_t();

    static void validateTLSKey();

    static void destructTLSData(void* data);

    static void setErrorEtcImpl(

            const char* caller, int line, EGLint error, bool quiet);