István Cserny / Mbed 2 deprecated Lab07_RTOS_philosophers

RTOS example - solving the Dining Philosophers problem by using mutexes

Dependencies:   mbed mbed-rtos

main.cpp@0:bc0e168010f0, 2022-02-24 (annotated)

Committer:
cspista
Date:
Thu Feb 24 08:09:20 2022 +0000
Revision:
0:bc0e168010f0
final version

Who changed what in which revision?

UserRevisionLine numberNew contents of line
cspista 0:bc0e168010f0 1 #include "mbed.h"
cspista 0:bc0e168010f0 2 #include "rtos.h"
cspista 0:bc0e168010f0 3 // Mutex stdio_mutex;
cspista 0:bc0e168010f0 4 Mutex chopstick[5]; //Array of mutexes representing the 5 chopsticks
cspista 0:bc0e168010f0 5 Serial pc(USBTX,USBRX); //UART via ST-Link
cspista 0:bc0e168010f0 6
cspista 0:bc0e168010f0 7 void notify(int num, int state)
cspista 0:bc0e168010f0 8 {
cspista 0:bc0e168010f0 9 // stdio_mutex.lock();
cspista 0:bc0e168010f0 10 if(state) {
cspista 0:bc0e168010f0 11 pc.printf("Philospher %d is EATING \n\r", num);
cspista 0:bc0e168010f0 12 } else {
cspista 0:bc0e168010f0 13 pc.printf("Philospher %d is thinking \n\r", num);
cspista 0:bc0e168010f0 14 }
cspista 0:bc0e168010f0 15 // stdio_mutex.unlock();
cspista 0:bc0e168010f0 16 }
cspista 0:bc0e168010f0 17
cspista 0:bc0e168010f0 18 void philosopher(void const *args)
cspista 0:bc0e168010f0 19 {
cspista 0:bc0e168010f0 20 while (true) {
cspista 0:bc0e168010f0 21 if(chopstick[(int)args-1].trylock()) {
cspista 0:bc0e168010f0 22 if(chopstick[(int)args%5].trylock()) {
cspista 0:bc0e168010f0 23 notify((int)args,1); //Start EATING
cspista 0:bc0e168010f0 24 Thread::wait(1000+rand()%1000);
cspista 0:bc0e168010f0 25 chopstick[(int)args%5].unlock(); //Release chopsticks
cspista 0:bc0e168010f0 26 chopstick[(int)args-1].unlock();
cspista 0:bc0e168010f0 27 notify((int)args,0); //Start Thinking
cspista 0:bc0e168010f0 28 Thread::wait(2000+rand()%2000); //Get's hungry after this time...
cspista 0:bc0e168010f0 29 } else {
cspista 0:bc0e168010f0 30 chopstick[(int)args-1].unlock();
cspista 0:bc0e168010f0 31 Thread::wait(100+rand()%100); //Wait for random time if failed
cspista 0:bc0e168010f0 32 }
cspista 0:bc0e168010f0 33 } else {
cspista 0:bc0e168010f0 34 Thread::wait(100+rand()%100); //Wait for random time if failed
cspista 0:bc0e168010f0 35 }
cspista 0:bc0e168010f0 36
cspista 0:bc0e168010f0 37 }
cspista 0:bc0e168010f0 38 }
cspista 0:bc0e168010f0 39
cspista 0:bc0e168010f0 40 int main()
cspista 0:bc0e168010f0 41 {
cspista 0:bc0e168010f0 42 pc.baud(115200);
cspista 0:bc0e168010f0 43 Thread t2(philosopher, (void *)2U);
cspista 0:bc0e168010f0 44 Thread t3(philosopher, (void *)3U);
cspista 0:bc0e168010f0 45 Thread t4(philosopher, (void *)4U);
cspista 0:bc0e168010f0 46 Thread t5(philosopher, (void *)5U);
cspista 0:bc0e168010f0 47 philosopher((void *)1U);
cspista 0:bc0e168010f0 48 }