sc_mutex

sc_mutex is a predefined primitive channel intended to model the behavior of a mutual exclusion lock as used to control access to a resource shared by concurrent processes.

 A mutex will be in one of two exclusive states: unlocked or locked. Only one process can lock a given mutex at one time. A mutex can only be unlocked by the particular process that locked the mutex, but may be locked subsequently by a different process.

sc_mutex class comes with pre-defined methods as below.

.

• int lock() : Lock the mutex if it is free, else wait till mutex gets free.
• int unlock() : Unlock the mutex
• int trylock() : Check if mutex is free, if free then lock it else return -1.
• char* kind() : Return string "sc_mutex"

Example : sc_mutex

  1 #include 

  2

  3 SC_MODULE (sc_mutex_example) {

  4   sc_in<bool> clock;

  5

  6   sc_mutex   bus;

  7   int     cnt;

  8

  9

 10   void do_bus(int who) {

 11     cout << "@" << sc_time_stamp() <<" Bus access by instance " << who << endl;

 12   }

 13

 14   void do_test1() {

 15     while (true) {

 16       wait();

 17       cout << "@" << sc_time_stamp() <<" Checking mutex intance 0"<<endl;

 18       // Check if mutex is available

 19       if (bus.trylock()  ! = -1) {

 20         cout << "@" << sc_time_stamp() <<" Got mutex for intance 0"<<endl;

 21         cnt ++;

 22         do_bus(0);

 23         wait(2);

 24         // Unlock the mutex

 25         bus.unlock();

 26       }

 27       if (cnt >= 3) {

 28         sc_stop(); // sc_stop triggers end of simulation

 29       }

 30     }

 31   }

 32

 33   void do_test2() {

 34     while (true) {

 35       wait();

 36       cout << "@" << sc_time_stamp() <<" Checking mutex intance 1"<<endl;

 37       // Wait till mutex is available

 38       bus.lock();

 39       cout << "@" << sc_time_stamp() <<" Got mutex for intance 1"<<endl;

 40       do_bus(1);

 41       wait(3);

 42       // Unlock the mutex

 43       bus.unlock();

 44     }

 45   }

 46

 47   SC_CTOR(sc_mutex_example) {

 48     cnt = 0;

 49     SC_CTHREAD(do_test1,clock.pos());

 50     SC_CTHREAD(do_test2,clock.pos());

 51   }

 52 };

 53

 54 int sc_main (int argc, char* argv[]) {

 55   sc_clock clock ("my_clock",1,0.5);

 56

 57   sc_mutex_example  object("wait");

 58     object.clock (clock.signal());

 59

 60   sc_start(0); // First time called will init schedular

 61   sc_start();  // Run the simulation till sc_stop is encountered

 62   return 0;// Terminate simulation

 63 }
Simulation Output : sc_mutex
 @1 ns Checking mutex intance 1

 @1 ns Got mutex for intance 1

 @1 ns Bus access by instance 1

 @1 ns Checking mutex intance 0

 @2 ns Checking mutex intance 0

 @3 ns Checking mutex intance 0

 @4 ns Checking mutex intance 0

 @4 ns Got mutex for intance 0

 @4 ns Bus access by instance 0

 @5 ns Checking mutex intance 1

 @7 ns Got mutex for intance 1

 @7 ns Bus access by instance 1

 @7 ns Checking mutex intance 0

 @8 ns Checking mutex intance 0

 @9 ns Checking mutex intance 0

 @10 ns Checking mutex intance 0

 @10 ns Got mutex for intance 0

 @10 ns Bus access by instance 0

 @11 ns Checking mutex intance 1

 @13 ns Got mutex for intance 1

 @13 ns Bus access by instance 1

 @13 ns Checking mutex intance 0

 @14 ns Checking mutex intance 0

 @15 ns Checking mutex intance 0

 @16 ns Checking mutex intance 0

 @16 ns Got mutex for intance 0

 @16 ns Bus access by instance 0

 @17 ns Checking mutex intance 1

 SystemC: simulation stopped by user.

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