posix: implement pthread_setschedprio

Implement posix pthread_setschedprio()

Signed-off-by: Gaetan Perrot <gaetanperrotpro@gmail.com>

include/zephyr/posix/pthread.h

@@ -447,6 +447,7 @@ int pthread_attr_setschedparam(pthread_attr_t *attr,
 			       const struct sched_param *schedparam);
 int pthread_setschedparam(pthread_t pthread, int policy,
 			  const struct sched_param *param);
+int pthread_setschedprio(pthread_t thread, int prio);
 int pthread_rwlock_destroy(pthread_rwlock_t *rwlock);
 int pthread_rwlock_init(pthread_rwlock_t *rwlock,
 			const pthread_rwlockattr_t *attr);

lib/posix/options/pthread.c

@@ -869,6 +869,46 @@ int pthread_setschedparam(pthread_t pthread, int policy, const struct sched_para
 	return ret;
 }
 
+/**
+ * @brief Set thread scheduling priority.
+ *
+ * See IEEE 1003.1
+ */
+int pthread_setschedprio(pthread_t thread, int prio)
+{
+	int ret = 0;
+	int new_prio = K_LOWEST_APPLICATION_THREAD_PRIO;
+	struct posix_thread *t = NULL;
+	int policy = 0;
+	struct sched_param param;
+
+	ret = pthread_getschedparam(thread, &policy, &param);
+
+	if (ret != 0) {
+		return ret;
+	}
+
+	if (!is_posix_policy_prio_valid(prio, policy)) {
+		return EINVAL;
+	}
+
+	K_SPINLOCK(&pthread_pool_lock) {
+		t = to_posix_thread(thread);
+		if (t == NULL) {
+			ret = ESRCH;
+			K_SPINLOCK_BREAK;
+		}
+
+		new_prio = posix_to_zephyr_priority(prio, policy);
+	}
+
+	if (ret == 0) {
+		k_thread_priority_set(&t->thread, new_prio);
+	}
+
+	return ret;
+}
+
 /**
  * @brief Initialise threads attribute object
  *