Solve the problem (+1)!

inc/globals.hpp

@@ -17,6 +17,6 @@ extern list lists[3];
 extern list *freelist, *list1, *list2;
 
 // count semaphores
-extern sem_t sem_freelist, sem_list1, sem_list2;
+extern sem_t sem_freelist, sem_list1, sem_list2, sem_freelist_minus_1;
 // binary semaphores
 extern sem_t mut_freelist, mut_list1, mut_list2;

src/consumer.cpp

@@ -9,19 +9,27 @@ int consume(block* c);
 void *consumer (void *) {
    block* c;
    while (true) {
+      // wait for element on list2
       wait(sem_list2);
+      // mutual exclusion for list2
       wait(mut_list2);
       //* c:=unlink(list-2);
       c = unlink(list2);
+      // mutual exclusion for list2
       signal(mut_list2);
 
       //* consume_information_in_block(c)
       consume(c);
 
+      // mutual exclusion for freelist
       wait(mut_freelist);
       //* link(c, freelist)
       link(c, freelist);
+      // mutual exclusion for freelist
       signal(mut_freelist);
+      // signal thread-1 to continue
+      signal(sem_freelist_minus_1);
+      // signal new element on freelist
       signal(sem_freelist);
 
    }
@@ -29,5 +37,5 @@ void *consumer (void *) {
 }
 
 int consume(block *c) {
-   return c->data;
+   return 0;
 }

src/main.cpp

@@ -16,11 +16,9 @@ list lists[3] = {0};
 list *freelist = &lists[0], *list1 = &lists[1], *list2 = &lists[2];
 
 // count semaphores
-sem_t sem_freelist, sem_list1, sem_list2;
+sem_t sem_freelist, sem_freelist_minus_1, sem_list1, sem_list2;
 // binary semaphores
 sem_t mut_freelist, mut_list1, mut_list2;
-// binary semaphores for reading/writing
-sem_t mut_take, mut_give;
 
 int main (int argc, char* argv[]) {
    // initialize the freelist
@@ -29,6 +27,7 @@ int main (int argc, char* argv[]) {
    //TODO: Implement a semaphore solution to the problem
    // counting semaphores measure the length
    sem_init(&sem_freelist, 0, freelist->length);
+   sem_init(&sem_freelist_minus_1, 0, freelist->length-1);
    sem_init(&sem_list1, 0, 0);
    sem_init(&sem_list2, 0, 0);
    // binary semaphores create mutual exclusion

src/producer.cpp

@@ -8,24 +8,29 @@ void produce(block* b);
 
 void *producer (void *) {
    block *b;
-   while (true)
+   while (true) {
-   {
+      // wait for >1 block on freelist
-      int v;
+      wait(sem_freelist_minus_1);
-      while(sem_getvalue(&sem_freelist, &v), v <= 1);
+      // wait for element on freelist
-      wait(sem_freelist); // wait for freelist not empty
+      wait(sem_freelist);
-      wait(mut_freelist); // lock freelist
+      // mutual exclusion for freelist
+      wait(mut_freelist);
       //* b:= unlink(freelist);
       b = unlink(freelist);
-      signal(mut_freelist); // unlock freelist
+      // mutual exclusion for freelist
+      signal(mut_freelist);
 
       //* produce_information_in_block(b)
       produce(b);
 
-      wait(mut_list1); // lock mutex
+      // mutual exclusion for list1
+      wait(mut_list1);
       //* link(b, list1);
       link(b, list1);
-      signal(mut_list1); // unlock mutex
+      // mutual exclusion for list1
-      signal(sem_list1); // signal new item on list
+      signal(mut_list1);
+      // signal new element on list1
+      signal(sem_list1);
    }
    return nullptr;
 }

src/transformer.cpp

@@ -9,31 +9,43 @@ void transform(block* x, block* y);
 void *transformer (void *) {
    block *x, *y;
    while (true) {
+      // wait for element on list1
       wait(sem_list1);
-      wait(sem_freelist);
+      // mutual exclusion for list1
       wait(mut_list1);
       //* x:=unlink(list1);
       x = unlink(list1);
+      // mutual exclusion for list1
       signal(mut_list1);
 
+      // wait for element on freelist
+      wait(sem_freelist);
+      // mutual exclusion for freelist
       wait(mut_freelist);
       //* y:=unlink(freelist);
       y = unlink(freelist);
+      // mutual exclusion for freelist
       signal(mut_freelist);
 
       //* use_block_x_to_produce_info_in_y(x,y)
       transform(x, y);
 
+      // mutual exclusion for freelist
       wait(mut_freelist);
       //* link(x, freelist);
       link(x, freelist);
+      // mutual exclusion for freelist
       signal(mut_freelist);
+      // freelist++
       signal(sem_freelist);
 
+      // mutual exclusion for list2
       wait(mut_list2);
       //* link(y, list2);
       link(y, list2);
+      // mutual exclusion for list2
       signal(mut_list2);
+      // signal new element on list2
       signal(sem_list2);
 
    }
@@ -41,5 +53,6 @@ void *transformer (void *) {
 }
 
 void transform(block *x, block *y) {
+   usleep(timescale);
    return;
 }