multithreading - Qt/C++: Recursive mutex, 'sync zones' and blocking signals -

firstly i'd point out i've looked can't find answer i'm looking for/have got confused overly detailed answers.

i have program uses 2 threads. boolean values need set , read in thread read in thread b.

thread a:

module::module(){ }  void module::foo(){     mutex.lock();     bool request = true;     mutex.unlock(); }  void module::bar(){     mutex.lock();     if (request){         mutex.unlock();         // stuff     }else{         mutex.unlock();     } }  

thread b:

provider::provider(){     module = new module;  // pointer class request 'lives in' }  void provider::foo(){     mutex.lock();     if (module->request){         mutex.unlock();         // stuff         }     }else{         mutex.unlock();     } } 

my question might seem rather trivial, it's bugged me. thread cannot read , write @ same time, i'd argue recursive mutex not required a. however, there small possibility foo() , bar() called simultaneous thread b (signals , slots). mean need recursive mutex?

also; there reason not use qt::blockingqueudconnection? colleague argued dangerous sends calling threads sleep until signal has executed slot- not sort of same mutex?

furthermore; seen post regarding structuring mutex (pthread mutex locking variables used in statements). in here mentions making local copies on values. if employ similar thread e.g.

mutex.lock(); requestcopy = request; mutex.lock(); ... if(requestcopy){ // stuff } 

will block access of request whereever requestcopy getting used? looking use style in code simplicity not work if read , write in thread?

any great.

from have shown, looks (rewritten)

some module (thread a):

class module { private:     bool request = false;     qmutex m; public:         void set_request(bool b) {         qmutexlocker lock(&m);         request = b;     }      bool get_request() {         qmutexlocker lock(&m);         return request;     }      void bar() {         if (get_request()) {             // stuff         }     } }; 

thread b:

class provider { public:     provider() {         module = new module();     }      void foo() {         if (module->get_request()){             // stuff         }     } private:     module *module; }; 

if case (and fine way), there no need recursive mutex.