[PATCH v2 0/1] Add KUnit tests for llist

[Artur Alves]

Hi all,

This is part of a hackathon organized by LKCAMP[1], focused on writing
tests using KUnit. We reached out a while ago asking for advice on what
would be a useful contribution[2] and ended up choosing data structures
that did not yet have tests.

This patch adds tests for the llist data structure, defined in
include/linux/llist.h, and is inspired by the KUnit tests for the doubly
linked list in lib/list-test.c[3].

It is important to note that this patch depends on the patch referenced
in [4], as it utilizes the newly created lib/tests/ subdirectory.

[1] https://lkcamp.dev/about/
[2] https://lore.kernel.org/all/Zktnt7rjKryTh9-N@arch/
[3] https://elixir.bootlin.com/linux/latest/source/lib/list-test.c
[4] https://lore.kernel.org/all/20240720181025...@kernel.org/

---
Changes in v2:
- Add MODULE_DESCRIPTION()
- Move the tests from lib/llist_kunit.c to lib/tests/llist_kunit.c
- Change the license from "GPL v2" to "GPL"

Artur Alves (1):
lib/llist_kunit.c: add KUnit tests for llist

lib/Kconfig.debug | 11 ++
lib/tests/Makefile | 1 +
lib/tests/llist_kunit.c | 361 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 373 insertions(+)
create mode 100644 lib/tests/llist_kunit.c

--
2.46.0

[Artur Alves]

Add KUnit tests for the llist data structure. They test the vast
majority of methods and macros defined in include/linux/llist.h.

These are inspired by the existing tests for the 'list' doubly
linked in lib/list-test.c [1]. Each test case (llist_test_x)
tests the behaviour of the llist function/macro 'x'.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/lib/list-test.c?h=v6.11-rc6

Signed-off-by: Artur Alves <artu...@gmail.com>
---

lib/Kconfig.debug | 11 ++
lib/tests/Makefile | 1 +
lib/tests/llist_kunit.c | 361 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 373 insertions(+)
create mode 100644 lib/tests/llist_kunit.c

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index a30c03a66172..b2725daccc52 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -2813,6 +2813,17 @@ config USERCOPY_KUNIT_TEST
on the copy_to/from_user infrastructure, making sure basic
user/kernel boundary testing is working.

+config LLIST_KUNIT_TEST
+ tristate "KUnit tests for lib/llist" if !KUNIT_ALL_TESTS
+ depends on KUNIT
+ default KUNIT_ALL_TESTS
+ help
+ This option builds the "llist_kunit" test module that
+ helps to verify the correctness of the functions and
+ macros defined in (<linux/llist.h>).
+
+ If unsure, say N.
+
config TEST_UDELAY
tristate "udelay test driver"
help
diff --git a/lib/tests/Makefile b/lib/tests/Makefile
index c6a14cc8663e..8d7c40a73110 100644
--- a/lib/tests/Makefile
+++ b/lib/tests/Makefile
@@ -34,4 +34,5 @@ CFLAGS_stackinit_kunit.o += $(call cc-disable-warning, switch-unreachable)
obj-$(CONFIG_STACKINIT_KUNIT_TEST) += stackinit_kunit.o
obj-$(CONFIG_STRING_KUNIT_TEST) += string_kunit.o
obj-$(CONFIG_STRING_HELPERS_KUNIT_TEST) += string_helpers_kunit.o
+obj-$(CONFIG_LLIST_KUNIT_TEST) += llist_kunit.o

diff --git a/lib/tests/llist_kunit.c b/lib/tests/llist_kunit.c
new file mode 100644
index 000000000000..f273c0d175c7
--- /dev/null
+++ b/lib/tests/llist_kunit.c
@@ -0,0 +1,361 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KUnit test for the Kernel lock-less linked-list structure.
+ *
+ * Author: Artur Alves <artu...@gmail.com>
+ */
+
+#include <kunit/test.h>
+#include <linux/llist.h>
+
+#define ENTRIES_SIZE 3
+
+struct llist_test_struct {
+ int data;
+ struct llist_node node;
+};
+
+static void llist_test_init_llist(struct kunit *test)
+{
+ /* test if the llist is correctly initialized */
+ struct llist_head llist1 = LLIST_HEAD_INIT(llist1);
+ LLIST_HEAD(llist2);
+ struct llist_head llist3, *llist4, *llist5;
+
+ KUNIT_EXPECT_TRUE(test, llist_empty(&llist1));
+
+ KUNIT_EXPECT_TRUE(test, llist_empty(&llist2));
+
+ init_llist_head(&llist3);
+ KUNIT_EXPECT_TRUE(test, llist_empty(&llist3));
+
+ llist4 = kzalloc(sizeof(*llist4), GFP_KERNEL | __GFP_NOFAIL);
+ init_llist_head(llist4);
+ KUNIT_EXPECT_TRUE(test, llist_empty(llist4));
+ kfree(llist4);
+
+ llist5 = kmalloc(sizeof(*llist5), GFP_KERNEL | __GFP_NOFAIL);
+ memset(llist5, 0xFF, sizeof(*llist5));
+ init_llist_head(llist5);
+ KUNIT_EXPECT_TRUE(test, llist_empty(llist5));
+ kfree(llist5);
+}
+
+static void llist_test_init_llist_node(struct kunit *test)
+{
+ struct llist_node a;
+
+ init_llist_node(&a);
+
+ KUNIT_EXPECT_PTR_EQ(test, a.next, &a);
+}
+
+static void llist_test_llist_entry(struct kunit *test)
+{
+ struct llist_test_struct test_struct, *aux;
+ struct llist_node *llist = &test_struct.node;
+
+ aux = llist_entry(llist, struct llist_test_struct, node);
+ KUNIT_EXPECT_PTR_EQ(test, &test_struct, aux);
+}
+
+static void llist_test_add(struct kunit *test)
+{
+ struct llist_node a, b;
+ LLIST_HEAD(llist);
+
+ init_llist_node(&a);
+ init_llist_node(&b);
+
+ /* The first assertion must be true, given that llist is empty */
+ KUNIT_EXPECT_TRUE(test, llist_add(&a, &llist));
+ KUNIT_EXPECT_FALSE(test, llist_add(&b, &llist));
+
+ /* Should be [List] -> b -> a */
+ KUNIT_EXPECT_PTR_EQ(test, llist.first, &b);
+ KUNIT_EXPECT_PTR_EQ(test, b.next, &a);
+}
+
+static void llist_test_add_batch(struct kunit *test)
+{
+ struct llist_node a, b, c;
+ LLIST_HEAD(llist);
+ LLIST_HEAD(llist2);
+
+ init_llist_node(&a);
+ init_llist_node(&b);
+ init_llist_node(&c);
+
+ llist_add(&a, &llist2);
+ llist_add(&b, &llist2);
+ llist_add(&c, &llist2);
+
+ /* This assertion must be true, given that llist is empty */
+ KUNIT_EXPECT_TRUE(test, llist_add_batch(&c, &a, &llist));
+
+ /* should be [List] -> c -> b -> a */
+ KUNIT_EXPECT_PTR_EQ(test, llist.first, &c);
+ KUNIT_EXPECT_PTR_EQ(test, c.next, &b);
+ KUNIT_EXPECT_PTR_EQ(test, b.next, &a);
+}
+
+static void llist_test_llist_next(struct kunit *test)
+{
+ struct llist_node a, b;
+ LLIST_HEAD(llist);
+
+ init_llist_node(&a);
+ init_llist_node(&b);
+
+ llist_add(&a, &llist);
+ llist_add(&b, &llist);
+
+ /* should be [List] -> b -> a */
+ KUNIT_EXPECT_PTR_EQ(test, llist_next(&b), &a);
+ KUNIT_EXPECT_NULL(test, llist_next(&a));
+}
+
+static void llist_test_empty_llist(struct kunit *test)
+{
+ struct llist_head llist = LLIST_HEAD_INIT(llist);
+ struct llist_node a;
+
+ KUNIT_EXPECT_TRUE(test, llist_empty(&llist));
+
+ llist_add(&a, &llist);
+
+ KUNIT_EXPECT_FALSE(test, llist_empty(&llist));
+}
+
+static void llist_test_llist_on_list(struct kunit *test)
+{
+ struct llist_node a, b;
+ LLIST_HEAD(llist);
+
+ init_llist_node(&a);
+ init_llist_node(&b);
+
+ llist_add(&a, &llist);
+
+ /* should be [List] -> a */
+ KUNIT_EXPECT_TRUE(test, llist_on_list(&a));
+ KUNIT_EXPECT_FALSE(test, llist_on_list(&b));
+}
+
+static void llist_test_del_first(struct kunit *test)
+{
+ struct llist_node a, b, *c;
+ LLIST_HEAD(llist);
+
+ llist_add(&a, &llist);
+ llist_add(&b, &llist);
+
+ /* before: [List] -> b -> a */
+ c = llist_del_first(&llist);
+
+ /* should be [List] -> a */
+ KUNIT_EXPECT_PTR_EQ(test, llist.first, &a);
+
+ /* del must return a pointer to llist_node b
+ * the returned pointer must be marked on list
+ */
+ KUNIT_EXPECT_PTR_EQ(test, c, &b);
+ KUNIT_EXPECT_TRUE(test, llist_on_list(c));
+}
+
+static void llist_test_del_first_init(struct kunit *test)
+{
+ struct llist_node a, *b;
+ LLIST_HEAD(llist);
+
+ llist_add(&a, &llist);
+
+ b = llist_del_first_init(&llist);
+
+ /* should be [List] */
+ KUNIT_EXPECT_TRUE(test, llist_empty(&llist));
+
+ /* the returned pointer must be marked out of the list */
+ KUNIT_EXPECT_FALSE(test, llist_on_list(b));
+}
+
+static void llist_test_del_first_this(struct kunit *test)
+{
+ struct llist_node a, b;
+ LLIST_HEAD(llist);
+
+ llist_add(&a, &llist);
+ llist_add(&b, &llist);
+
+ llist_del_first_this(&llist, &a);
+
+ /* before: [List] -> b -> a */
+
+ // should remove only if is the first node in the llist
+ KUNIT_EXPECT_FALSE(test, llist_del_first_this(&llist, &a));
+
+ KUNIT_EXPECT_TRUE(test, llist_del_first_this(&llist, &b));
+
+ /* should be [List] -> a */
+ KUNIT_EXPECT_PTR_EQ(test, llist.first, &a);
+}
+
+static void llist_test_del_all(struct kunit *test)
+{
+ struct llist_node a, b;
+ LLIST_HEAD(llist);
+ LLIST_HEAD(empty_llist);
+
+ llist_add(&a, &llist);
+ llist_add(&b, &llist);
+
+ /* deleting from a empty llist should return NULL */
+ KUNIT_EXPECT_NULL(test, llist_del_all(&empty_llist));
+
+ llist_del_all(&llist);
+
+ KUNIT_EXPECT_TRUE(test, llist_empty(&llist));
+}
+
+static void llist_test_for_each(struct kunit *test)
+{
+ struct llist_node entries[ENTRIES_SIZE] = { 0 };
+ struct llist_node *pos, *deleted_nodes;
+ LLIST_HEAD(llist);
+ int i = 0;
+
+ for (int i = ENTRIES_SIZE - 1; i >= 0; i--)
+ llist_add(&entries[i], &llist);
+
+ /* before [List] -> entries[0] -> ... -> entries[ENTRIES_SIZE - 1] */
+ llist_for_each(pos, llist.first) {
+ KUNIT_EXPECT_PTR_EQ(test, pos, &entries[i++]);
+ }
+
+ KUNIT_EXPECT_EQ(test, ENTRIES_SIZE, i);
+
+ i = 0;
+
+ /* traversing deleted nodes */
+ deleted_nodes = llist_del_all(&llist);
+
+ llist_for_each(pos, deleted_nodes) {
+ KUNIT_EXPECT_PTR_EQ(test, pos, &entries[i++]);
+ }
+
+ KUNIT_EXPECT_EQ(test, ENTRIES_SIZE, i);
+}
+
+static void llist_test_for_each_safe(struct kunit *test)
+{
+ struct llist_node entries[ENTRIES_SIZE] = { 0 };
+ struct llist_node *pos, *n;
+ LLIST_HEAD(llist);
+ int i = 0;
+
+ for (int i = ENTRIES_SIZE - 1; i >= 0; i--)
+ llist_add(&entries[i], &llist);
+
+ llist_for_each_safe(pos, n, llist.first) {
+ KUNIT_EXPECT_PTR_EQ(test, pos, &entries[i++]);
+ llist_del_first(&llist);
+ }
+
+ KUNIT_EXPECT_EQ(test, ENTRIES_SIZE, i);
+ KUNIT_EXPECT_TRUE(test, llist_empty(&llist));
+}
+
+static void llist_test_for_each_entry(struct kunit *test)
+{
+ struct llist_test_struct entries[ENTRIES_SIZE], *pos;
+ LLIST_HEAD(llist);
+ int i = 0;
+
+ for (int i = ENTRIES_SIZE - 1; i >= 0; --i) {
+ entries[i].data = i;
+ llist_add(&entries[i].node, &llist);
+ }
+
+ i = 0;
+
+ llist_for_each_entry(pos, llist.first, node) {
+ KUNIT_EXPECT_EQ(test, pos->data, i);
+ i++;
+ }
+
+ KUNIT_EXPECT_EQ(test, ENTRIES_SIZE, i);
+}
+
+static void llist_test_for_each_entry_safe(struct kunit *test)
+{
+ struct llist_test_struct entries[ENTRIES_SIZE], *pos, *n;
+ LLIST_HEAD(llist);
+ int i = 0;
+
+ for (int i = ENTRIES_SIZE - 1; i >= 0; --i) {
+ entries[i].data = i;
+ llist_add(&entries[i].node, &llist);
+ }
+
+ i = 0;
+
+ llist_for_each_entry_safe(pos, n, llist.first, node) {
+ KUNIT_EXPECT_EQ(test, pos->data, i++);
+ llist_del_first(&llist);
+ }
+
+ KUNIT_EXPECT_EQ(test, ENTRIES_SIZE, i);
+ KUNIT_EXPECT_TRUE(test, llist_empty(&llist));
+}
+
+static void llist_test_reverse_order(struct kunit *test)
+{
+ struct llist_node entries[3], *pos, *reversed_llist;
+ LLIST_HEAD(llist);
+ int i = 0;
+
+ llist_add(&entries[0], &llist);
+ llist_add(&entries[1], &llist);
+ llist_add(&entries[2], &llist);
+
+ /* before [List] -> entries[2] -> entries[1] -> entries[0] */
+ reversed_llist = llist_reverse_order(llist_del_first(&llist));
+
+ /* should be [List] -> entries[0] -> entries[1] -> entrires[2] */
+ llist_for_each(pos, reversed_llist) {
+ KUNIT_EXPECT_PTR_EQ(test, pos, &entries[i++]);
+ }
+
+ KUNIT_EXPECT_EQ(test, 3, i);
+}
+
+static struct kunit_case llist_test_cases[] = {
+ KUNIT_CASE(llist_test_init_llist),
+ KUNIT_CASE(llist_test_init_llist_node),
+ KUNIT_CASE(llist_test_llist_entry),
+ KUNIT_CASE(llist_test_add),
+ KUNIT_CASE(llist_test_add_batch),
+ KUNIT_CASE(llist_test_llist_next),
+ KUNIT_CASE(llist_test_empty_llist),
+ KUNIT_CASE(llist_test_llist_on_list),
+ KUNIT_CASE(llist_test_del_first),
+ KUNIT_CASE(llist_test_del_first_init),
+ KUNIT_CASE(llist_test_del_first_this),
+ KUNIT_CASE(llist_test_del_all),
+ KUNIT_CASE(llist_test_for_each),
+ KUNIT_CASE(llist_test_for_each_safe),
+ KUNIT_CASE(llist_test_for_each_entry),
+ KUNIT_CASE(llist_test_for_each_entry_safe),
+ KUNIT_CASE(llist_test_reverse_order),
+ {}
+};
+
+static struct kunit_suite llist_test_suite = {
+ .name = "llist",
+ .test_cases = llist_test_cases,
+};
+
+kunit_test_suite(llist_test_suite);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("KUnit tests for the llist data structure.");
--
2.46.0

[Rae Moar]

On Tue, Sep 3, 2024 at 5:40 PM Artur Alves <artu...@gmail.com> wrote:
>
> Add KUnit tests for the llist data structure. They test the vast
> majority of methods and macros defined in include/linux/llist.h.
>
> These are inspired by the existing tests for the 'list' doubly
> linked in lib/list-test.c [1]. Each test case (llist_test_x)
> tests the behaviour of the llist function/macro 'x'.
>
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/lib/list-test.c?h=v6.11-rc6
>
> Signed-off-by: Artur Alves <artu...@gmail.com>

Hello!

Thanks for creating this new test! It looks really good and is passing
all the tests.

My main comment is that this patch is causing some checkpatch warnings:

WARNING: Prefer a maximum 75 chars per line (possible unwrapped
commit description?)
#13:
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/lib/list-test.c?h=v6.11-rc6

It's probably fine to ignore this warning as it is a link. But I might
remove the link because it is not absolutely necessary in this case.

WARNING: added, moved or deleted file(s), does MAINTAINERS need updating?
#58:
new file mode 100644

ERROR: that open brace { should be on the previous line
#306: FILE: lib/llist_kunit.c:249:

+static void llist_test_for_each_safe(struct kunit *test)
+{

ERROR: that open brace { should be on the previous line
#325: FILE: lib/llist_kunit.c:268:

+static void llist_test_for_each_entry(struct kunit *test)
+{

ERROR: that open brace { should be on the previous line
#346: FILE: lib/llist_kunit.c:289:

+static void llist_test_for_each_entry_safe(struct kunit *test)
+{

These checkpatch errors are mistaken since the open brace should be
where it is. I believe this is getting picked up because of the
"for_each" in the test name. This was fixed for me by rewriting the
test names: from "llist_test_for_each_safe" -> to
"llist_test_safe_for_each", and so on for the other tests with errors.
Sorry it's a pain to change this but I think it is a better fix than
changing the checkpatch script.

> ---
> lib/Kconfig.debug | 11 ++
> lib/tests/Makefile | 1 +
> lib/tests/llist_kunit.c | 361 ++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 373 insertions(+)
> create mode 100644 lib/tests/llist_kunit.c
>
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index a30c03a66172..b2725daccc52 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -2813,6 +2813,17 @@ config USERCOPY_KUNIT_TEST
> on the copy_to/from_user infrastructure, making sure basic
> user/kernel boundary testing is working.
>
> +config LLIST_KUNIT_TEST
> + tristate "KUnit tests for lib/llist" if !KUNIT_ALL_TESTS
> + depends on KUNIT
> + default KUNIT_ALL_TESTS
> + help
> + This option builds the "llist_kunit" test module that
> + helps to verify the correctness of the functions and
> + macros defined in (<linux/llist.h>).

Also, I think I would prefer if this description was a bit tweaked.
Saying it builds the "module" is confusing since this test might be
run built-in instead. So maybe something more similar to :

This builds the llist (lock-less list) KUnit test suite. It tests the
API and basic functionality of the macros and functions defined in
<linux/llish.h>.

This is super nitpicky but I think I would prefer if you set two
variables to zero at the beginning rather than reusing "i". So: int i
= 0, j = 0;

> +
> + /* traversing deleted nodes */
> + deleted_nodes = llist_del_all(&llist);
> +
> + llist_for_each(pos, deleted_nodes) {
> + KUNIT_EXPECT_PTR_EQ(test, pos, &entries[i++]);
> + }
> +
> + KUNIT_EXPECT_EQ(test, ENTRIES_SIZE, i);
> +}
> +
> +static void llist_test_for_each_safe(struct kunit *test)
> +{
> + struct llist_node entries[ENTRIES_SIZE] = { 0 };

I'm not sure if it is necessary to initialize this to be zeros.

Rather than using the "3" here I would prefer using the ENTRIES_SIZE.

> + LLIST_HEAD(llist);
> + int i = 0;
> +
> + llist_add(&entries[0], &llist);
> + llist_add(&entries[1], &llist);
> + llist_add(&entries[2], &llist);
> +
> + /* before [List] -> entries[2] -> entries[1] -> entries[0] */
> + reversed_llist = llist_reverse_order(llist_del_first(&llist));
> +
> + /* should be [List] -> entries[0] -> entries[1] -> entrires[2] */

Small typo in this comment: "entries"

> + llist_for_each(pos, reversed_llist) {
> + KUNIT_EXPECT_PTR_EQ(test, pos, &entries[i++]);
> + }
> +
> + KUNIT_EXPECT_EQ(test, 3, i);

Same here with the use of the "3".

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[Artur Alves Cavalcante de Barros]

Hi!

Thanks for the reply! I'm going to address these issues ASAP :)