feat: add mutex prio to prevent deadlock on mutex

src/thread/thread.c

@@ -22,6 +22,7 @@
 #define WAITED (1 << 3)
 #define MUTEX_WAITING (1 << 4)
 #define MUTEX_LOCKING (1 << 5)
+#define MUTEX_MAXPRIO 5
 #define IS_WAITED(entry) (HAS_STATUS(entry, WAITED))
 #define IS_MUTEX_WAITING(entry) (HAS_STATUS(entry, MUTEX_WAITING))
 
@@ -53,6 +54,7 @@ struct context_entry_t {
     struct mutex_fifo_entry_t mutex_fifo_entry;
     int valgrind_id;
     int status;
+    int mutex_prio;
     char stack[STACK_SIZE];
 };
 
@@ -86,8 +88,13 @@ int thread_yield(void)
     }
 
     if (HAS_STATUS(running, MUTEX_LOCKING)) {
-        DBG("skip yield : running thread is locking a mutex");
+        if (running->mutex_prio > 0) {
-        return 0;
+            running->mutex_prio--;
+            DBG("skip yield : running thread is locking a mutex");
+            return 0;
+        }
+        else
+            running->mutex_prio = MUTEX_MAXPRIO;
     }
 
 #ifdef FIBO_STRAT
@@ -167,6 +174,7 @@ int thread_create(thread_t* newthread, void* (*func)(void*), void* funcarg)
     new_entry->status = ALLOCATED;
     new_entry->retvalue = NULL;
     new_entry->last_waited = NULL;
+    new_entry->mutex_prio = MUTEX_MAXPRIO;
 
     *newthread = new_entry;
 
@@ -430,6 +438,7 @@ int thread_mutex_lock(thread_mutex_t* mutex)
         thread_yield();
     }
     SET_STATUS(running, MUTEX_LOCKING);
+    running->mutex_prio = MUTEX_MAXPRIO;
 
     mutex->dummy = 1;
     return 0;