kernel: message does not execute correct put front behavior

When the buffer is full, Thread A gets pended (blocked).
If Thread B later calls the get function, it will unpend Thread A,
allowing it to resume and put the message into the queue.
In this situation, we need to know whether Thread A should
continue with put to front or put to end.

In order to resolve this issue, we don't allow set timeout
parameter for `k_msgq_put_front` and this parameter is always
`K_NO_WAIT`.

Signed-off-by: TaiJu Wu <[email protected]>

Author: TaiJuWu

include/zephyr/kernel.h

@@ -5000,18 +5000,17 @@ __syscall int k_msgq_put(struct k_msgq *msgq, const void *data, k_timeout_t time
  * pointer is not retained, so the message content will not be modified
  * by this function.
  *
+ * @note k_msgq_put_front() does not block.
+ *
  * @funcprops \isr_ok
  *
  * @param msgq Address of the message queue.
  * @param data Pointer to the message.
- * @param timeout Waiting period to add the message, or one of the special
- *                values K_NO_WAIT and K_FOREVER.
  *
  * @retval 0 Message sent.
  * @retval -ENOMSG Returned without waiting or queue purged.
- * @retval -EAGAIN Waiting period timed out.
  */
-__syscall int k_msgq_put_front(struct k_msgq *msgq, const void *data, k_timeout_t timeout);
+__syscall int k_msgq_put_front(struct k_msgq *msgq, const void *data);
 
 /**
  * @brief Receive a message from a message queue.

kernel/msg_q.c

@@ -228,9 +228,9 @@ int z_impl_k_msgq_put(struct k_msgq *msgq, const void *data, k_timeout_t timeout
 	return put_msg_in_queue(msgq, data, timeout, true);
 }
 
-int z_impl_k_msgq_put_front(struct k_msgq *msgq, const void *data, k_timeout_t timeout)
+int z_impl_k_msgq_put_front(struct k_msgq *msgq, const void *data)
 {
-	return put_msg_in_queue(msgq, data, timeout, false);
+	return put_msg_in_queue(msgq, data, K_NO_WAIT, false);
 }
 
 #ifdef CONFIG_USERSPACE
@@ -244,13 +244,12 @@ static inline int z_vrfy_k_msgq_put(struct k_msgq *msgq, const void *data,
 }
 #include <zephyr/syscalls/k_msgq_put_mrsh.c>
 
-static inline int z_vrfy_k_msgq_put_front(struct k_msgq *msgq, const void *data,
-				    k_timeout_t timeout)
+static inline int z_vrfy_k_msgq_put_front(struct k_msgq *msgq, const void *data)
 {
 	K_OOPS(K_SYSCALL_OBJ(msgq, K_OBJ_MSGQ));
 	K_OOPS(K_SYSCALL_MEMORY_READ(data, msgq->msg_size));
 
-	return z_impl_k_msgq_put_front(msgq, data, timeout);
+	return z_impl_k_msgq_put_front(msgq, data);
 }
 #include <zephyr/syscalls/k_msgq_put_front_mrsh.c>
 #endif /* CONFIG_USERSPACE */

samples/kernel/msg_queue/src/main.c

@@ -32,7 +32,7 @@ void producer_function(void *rec, void *p2, void *p3)
 			normal_data++;
 		}
 		printk("[producer] sending: %c (urgent)\n", urgent_data);
-		k_msgq_put_front(&my_msgq, &urgent_data, K_NO_WAIT);
+		k_msgq_put_front(&my_msgq, &urgent_data);
 		k_sleep(K_MSEC(100));
 		urgent_data++;