void barber_function(void *arg) {
barber_data *barber = (barber_data *)arg;
customer_data *customer;
syscall_lock_acquire(&barber_lock);
while (1) {
printf("Barber #%d looking for new customers\n", barber->id);
if (next_customer == NULL) {
syscall_condition_signal(&sitting_cond, &barber_lock);
syscall_condition_signal(&standing_cond, &barber_lock);
printf("Barber #%d sleeping\n", barber->id);
syscall_condition_wait(&barber_cond, &barber_lock);
printf("Barber #%d got woken up!\n", barber->id);
}
customer = next_customer;
next_customer = NULL;
printf("Barber #%d servicing customer #%d\n", barber->id, customer->id);
syscall_lock_release(&barber_lock);
simulatedwait(100000);
syscall_lock_acquire(&barber_lock);
printf("Barber #%d done servicing customer #%d\n", barber->id, customer->id);
syscall_condition_signal(&customer->cond, &barber_lock);
}
}
void customer_function(void *arg) {
customer_data *customer = (customer_data *)arg;
syscall_lock_acquire(&barber_lock);
printf("Customer #%d arrives\n", customer->id);
if (sitting + standing >= MAX_WAITING) {
printf("Barbershop full. Customer #%d leaving\n", customer->id);
syscall_lock_release(&barber_lock);
syscall_exit(0);
}
if (sitting >= MAX_SITTING) {
printf("Chairs occupied. Customer #%d standing in line\n", customer->id);
standing++;
syscall_condition_wait(&standing_cond, &barber_lock);
standing--;
}
if (sitting <= MAX_SITTING && next_customer != NULL) {
printf("Customer #%d takes a seat\n", customer->id);
sitting++;
syscall_condition_wait(&sitting_cond, &barber_lock);
sitting--;
}
printf("Customer #%d is being serviced\n", customer->id);
next_customer = customer;
syscall_condition_signal(&barber_cond, &barber_lock);
syscall_condition_wait(&customer->cond, &barber_lock);
syscall_lock_release(&barber_lock);
syscall_exit(0);
}
int main() {
syscall_lock_create(&baton_lock);
syscall_lock_acquire(&baton_lock);
// Setup data for threads
thread_data data[THREADS];
int i;
for(i=0; i<(THREADS); i++) {
data[i].id = i;
data[i].baton = 0;
data[i].countdown = 0;
syscall_condition_create(&data[i].cond);
data[i].next = &data[(i+1)%THREADS];
syscall_fork((void (*)(int))(&thread_function), (int)&data[i]);
}
// Setup special data for the first thread
data[0].countdown = ROUNDS;
data[0].baton = 1;
// Start first thread
syscall_condition_signal(&data[0].cond, &baton_lock);
syscall_lock_release(&baton_lock);
syscall_exit(0);
return 0;
}
void thread_function(void *arg){
thread_data *data = (thread_data *)arg;
while(1) {
syscall_lock_acquire(&baton_lock);
// Wait until baton is non-zero (meaning that the thread
// has the baton)
while(data->baton == 0) {
syscall_condition_wait(&data->cond, &baton_lock);
}
// First thread should perform countdown
if(data->id == 0) {
printf("\n%d: New round\n", data->id);
if(--data->countdown == 0) {
data->baton = -1; // create a stop baton
}
}
// Pass the baton on to the next thread
printf("%d: passing the baton on to %d\n", data->id,
data->next->id);
data->next->baton = data->baton;
// Quit if the baton was a stop baton
if(data->baton < 0){
printf("%d: I quit.\n",data->id);
syscall_condition_signal(&data->next->cond,
&baton_lock);
syscall_lock_release(&baton_lock);
syscall_exit(0);
}
//Remove baton from self and signal the next thread
data->baton = 0;
syscall_condition_signal(&data->next->cond, &baton_lock);
syscall_lock_release(&baton_lock);
}
}
/**
* Handle system calls. Interrupts are enabled when this function is
* called.
*
* @param user_context The userland context (CPU registers as they
* where when system call instruction was called in userland)
*/
void syscall_handle(context_t *user_context)
{
/* When a syscall is executed in userland, register a0 contains
* the number of the syscall. Registers a1, a2 and a3 contain the
* arguments of the syscall. The userland code expects that after
* returning from the syscall instruction the return value of the
* syscall is found in register v0. Before entering this function
* the userland context has been saved to user_context and after
* returning from this function the userland context will be
* restored from user_context.
*/
switch(user_context->cpu_regs[MIPS_REGISTER_A0]) {
case SYSCALL_HALT:
halt_kernel();
break;
case SYSCALL_EXIT:
syscall_exit(user_context->cpu_regs[MIPS_REGISTER_A1]);
break;
case SYSCALL_WRITE:
user_context->cpu_regs[MIPS_REGISTER_V0] =
syscall_write(user_context->cpu_regs[MIPS_REGISTER_A1],
(char*)user_context->cpu_regs[MIPS_REGISTER_A2],
(user_context->cpu_regs[MIPS_REGISTER_A3]));
break;
case SYSCALL_READ:
user_context->cpu_regs[MIPS_REGISTER_V0] =
syscall_read(user_context->cpu_regs[MIPS_REGISTER_A1],
(char*)user_context->cpu_regs[MIPS_REGISTER_A2],
(user_context->cpu_regs[MIPS_REGISTER_A3]));
break;
case SYSCALL_JOIN:
user_context->cpu_regs[MIPS_REGISTER_V0] =
syscall_join(user_context->cpu_regs[MIPS_REGISTER_A1]);
break;
case SYSCALL_EXEC:
user_context->cpu_regs[MIPS_REGISTER_V0] =
syscall_exec((char*)user_context->cpu_regs[MIPS_REGISTER_A1]);
break;
case SYSCALL_FORK:
user_context->cpu_regs[MIPS_REGISTER_V0] =
syscall_fork((void (*)(int))user_context->cpu_regs[MIPS_REGISTER_A1],
user_context->cpu_regs[MIPS_REGISTER_A2]);
break;
case SYSCALL_LOCK_CREATE:
user_context->cpu_regs[MIPS_REGISTER_V0] =
syscall_lock_create((lock_t*) user_context->cpu_regs[MIPS_REGISTER_A1]);
break;
case SYSCALL_LOCK_ACQUIRE:
syscall_lock_acquire((lock_t*) user_context->cpu_regs[MIPS_REGISTER_A1]);
break;
case SYSCALL_LOCK_RELEASE:
syscall_lock_release((lock_t*) user_context->cpu_regs[MIPS_REGISTER_A1]);
break;
case SYSCALL_CONDITION_CREATE:
user_context->cpu_regs[MIPS_REGISTER_V0] =
syscall_condition_create((cond_t*) user_context->cpu_regs[MIPS_REGISTER_A1]);
break;
case SYSCALL_CONDITION_WAIT:
syscall_condition_wait((cond_t*) user_context->cpu_regs[MIPS_REGISTER_A1],
(lock_t*) user_context->cpu_regs[MIPS_REGISTER_A2]);
break;
case SYSCALL_CONDITION_SIGNAL:
syscall_condition_signal((cond_t*) user_context->cpu_regs[MIPS_REGISTER_A1],
(lock_t*) user_context->cpu_regs[MIPS_REGISTER_A2]);
break;
case SYSCALL_CONDITION_BROADCAST:
syscall_condition_broadcast((cond_t*) user_context->cpu_regs[MIPS_REGISTER_A1],
(lock_t*) user_context->cpu_regs[MIPS_REGISTER_A2]);
break;
default:
KERNEL_PANIC("Unhandled system call\n");
}
/* Move to next instruction after system call */
user_context->pc += 4;
}
