kernel: pipe: fix !K_NO_WAIT and >= min_xfer bytes transferred

If timeout != K_NO_WAIT, then return immediately when not all
bytes_to_read or bytes_to_write have been transfered, but >=
min_xfer have been transferred.

Fixes zephyrproject-rtos#24485

Signed-off-by: Christopher Friedt <chrisfriedt@gmail.com>

kernel/pipes.c

@@ -529,7 +529,20 @@ int z_pipe_put_internal(struct k_pipe *pipe, struct k_pipe_async *async_desc,
 		return 0;
 	}
 
-	/* Not all data was copied. */
+	if (!K_TIMEOUT_EQ(timeout, K_NO_WAIT)
+	    && num_bytes_written >= min_xfer
+	    && min_xfer > 0) {
+		*bytes_written = num_bytes_written;
+#if (CONFIG_NUM_PIPE_ASYNC_MSGS > 0)
+		if (async_desc != NULL) {
+			pipe_async_finish(async_desc);
+		}
+#endif
+		k_sched_unlock();
+		return 0;
+	}
+
+	/* Not all data was copied */
 
 #if (CONFIG_NUM_PIPE_ASYNC_MSGS > 0)
 	if (async_desc != NULL) {
@@ -695,7 +708,17 @@ int z_impl_k_pipe_get(struct k_pipe *pipe, void *data, size_t bytes_to_read,
 		return 0;
 	}
 
-	/* Not all data was read. */
+	if (!K_TIMEOUT_EQ(timeout, K_NO_WAIT)
+	    && num_bytes_read >= min_xfer
+	    && min_xfer > 0) {
+		k_sched_unlock();
+
+		*bytes_read = num_bytes_read;
+
+		return 0;
+	}
+
+	/* Not all data was read */
 
 	struct k_pipe_desc  pipe_desc;
 

tests/kernel/pipe/pipe/src/main.c

@@ -14,6 +14,8 @@ extern void test_pipe_get_on_empty_pipe(void);
 extern void test_pipe_forever_timeout(void);
 extern void test_pipe_get_timeout(void);
 extern void test_pipe_get_invalid_size(void);
+extern void test_pipe_get_min_xfer(void);
+extern void test_pipe_put_min_xfer(void);
 
 extern struct k_pipe test_pipe;
 extern struct k_sem put_sem, get_sem, sync_sem, multiple_send_sem;
@@ -36,7 +38,9 @@ void test_main(void)
 			 ztest_user_unit_test(test_pipe_get_on_empty_pipe),
 			 ztest_user_unit_test(test_pipe_forever_timeout),
 			 ztest_user_unit_test(test_pipe_get_timeout),
-			 ztest_user_unit_test(test_pipe_get_invalid_size)
+			 ztest_user_unit_test(test_pipe_get_invalid_size),
+			 ztest_user_unit_test(test_pipe_get_min_xfer),
+			 ztest_user_unit_test(test_pipe_put_min_xfer)
 			 );
 
 	ztest_run_test_suite(test_pipe);

tests/kernel/pipe/pipe/src/test_pipe.c

@@ -97,8 +97,6 @@ static const struct pipe_sequence wait_elements[] = {
 	{ PIPE_SIZE + 1, ALL_BYTES, PIPE_SIZE + 1, RETURN_SUCCESS },
 
 	{ PIPE_SIZE - 1, ATLEAST_1, PIPE_SIZE - 1, RETURN_SUCCESS },
-	{    PIPE_SIZE, ATLEAST_1,     PIPE_SIZE, RETURN_SUCCESS },
-	{ PIPE_SIZE + 1, ATLEAST_1, PIPE_SIZE + 1, RETURN_SUCCESS }
 };
 
 static const struct pipe_sequence timeout_elements[] = {
@@ -826,3 +824,53 @@ void test_pipe_get_invalid_size(void)
 	zassert_equal(ret, -EINVAL,
 		      "fault didn't occur for min_xfer <= bytes_to_read");
 }
+
+/**
+ * @brief Test pipe get returns immediately if >= min_xfer is available
+ * @ingroup kernel_pipe_tests
+ * @see k_pipe_get()
+ */
+void test_pipe_get_min_xfer(void)
+{
+	int res;
+	size_t bytes_written = 0;
+	size_t bytes_read = 0;
+	char buf[8] = {};
+
+	res = k_pipe_put(&test_pipe, "Hi!", 3, &bytes_written,
+			 3 /* min_xfer */, K_FOREVER);
+	zassert_equal(res, 0, "did not write entire message");
+	zassert_equal(bytes_written, 3, "did not write entire message");
+
+	res = k_pipe_get(&test_pipe, buf, sizeof(buf), &bytes_read,
+			 1 /* min_xfer */, K_FOREVER);
+	zassert_equal(res, 0, "did not read at least one byte");
+	zassert_equal(bytes_read, 3, "did not read all bytes available");
+}
+
+/**
+ * @brief Test pipe put returns immediately if >= min_xfer is available
+ * @ingroup kernel_pipe_tests
+ * @see k_pipe_put()
+ */
+void test_pipe_put_min_xfer(void)
+{
+	int res;
+	size_t bytes_written = 0;
+
+	/* write 6 bytes into the pipe, so that 2 bytes are still free */
+	for (size_t i = 0; i < 2; ++i) {
+		bytes_written = 0;
+		res = k_pipe_put(&test_pipe, "Hi!", 3, &bytes_written,
+				 3 /* min_xfer */, K_FOREVER);
+		zassert_equal(res, 0, "did not write entire message");
+		zassert_equal(bytes_written, 3, "did not write entire message");
+	}
+
+	/* attempt to write 3 bytes, but allow success if >= 1 byte */
+	bytes_written = 0;
+	res = k_pipe_put(&test_pipe, "Hi!", 3, &bytes_written,
+			 1 /* min_xfer */, K_FOREVER);
+	zassert_equal(res, 0, "did not write min_xfer");
+	zassert_true(bytes_written >= 1, "did not write min_xfer");
+}