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[PATCH] lib: skip percpu_counter_tree boundary kunit tests on single-CPU

David Carlier posted 1 patch 2 weeks, 6 days ago
There is a newer version of this series
lib/tests/percpu_counter_tree_kunit.c | 6 ++++++
1 file changed, 6 insertions(+)
[PATCH] lib: skip percpu_counter_tree boundary kunit tests on single-CPU
Posted by David Carlier 2 weeks, 6 days ago 
On single-CPU topologies, accuracy_multiplier is zero, making both
approx_accuracy_range.under and .over zero. The boundary tests in
hpcc_test_compare_value_boundaries and hpcc_test_compare_counter_boundaries
then degenerate to comparing 0 vs 0, which correctly returns 0 (equal)
but the tests expect nonzero results.

Skip these boundary tests with kunit_skip() when accuracy is zero,
since approximation boundaries are meaningless without multi-CPU carry
propagation.

Fixes: ebc1ff504f55 ("lib: add kunit boundary tests for percpu_counter_tree comparisons")
Signed-off-by: David Carlier <devnexen@gmail.com>
---
 lib/tests/percpu_counter_tree_kunit.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/lib/tests/percpu_counter_tree_kunit.c b/lib/tests/percpu_counter_tree_kunit.c
index 4d058bc78f7d..609992bfaa21 100644
--- a/lib/tests/percpu_counter_tree_kunit.c
+++ b/lib/tests/percpu_counter_tree_kunit.c
@@ -101,6 +101,9 @@ static void hpcc_test_compare_value_boundaries(struct kunit *test)
 	percpu_counter_tree_set(&pct, 0);
 	percpu_counter_tree_approximate_accuracy_range(&pct, &under, &over);
 
+	if (!under && !over)
+		kunit_skip(test, "no approximation accuracy on single-CPU topology");
+
 	/*
 	 * With approx_sum = precise_sum = 0, from the accuracy invariant:
 	 *   approx_sum - over <= precise_sum <= approx_sum + under
@@ -214,6 +217,9 @@ static void hpcc_test_compare_counter_boundaries(struct kunit *test)
 	 */
 	combined = under + over;
 
+	if (!combined)
+		kunit_skip(test, "no approximation accuracy on single-CPU topology");
+
 	/* --- percpu_counter_tree_approximate_compare --- */
 
 	/* At boundary: indeterminate */
-- 
2.53.0
Re: [PATCH] lib: skip percpu_counter_tree boundary kunit tests on single-CPU
Posted by Josh Law 2 weeks, 6 days ago 

On 17 March 2026 15:06:38 GMT, David Carlier <devnexen@gmail.com> wrote:
>On single-CPU topologies, accuracy_multiplier is zero, making both
>approx_accuracy_range.under and .over zero. The boundary tests in
>hpcc_test_compare_value_boundaries and hpcc_test_compare_counter_boundaries
>then degenerate to comparing 0 vs 0, which correctly returns 0 (equal)
>but the tests expect nonzero results.
>
>Skip these boundary tests with kunit_skip() when accuracy is zero,
>since approximation boundaries are meaningless without multi-CPU carry
>propagation.
>
>Fixes: ebc1ff504f55 ("lib: add kunit boundary tests for percpu_counter_tree comparisons")
>Signed-off-by: David Carlier <devnexen@gmail.com>
>---
> lib/tests/percpu_counter_tree_kunit.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
>diff --git a/lib/tests/percpu_counter_tree_kunit.c b/lib/tests/percpu_counter_tree_kunit.c
>index 4d058bc78f7d..609992bfaa21 100644
>--- a/lib/tests/percpu_counter_tree_kunit.c
>+++ b/lib/tests/percpu_counter_tree_kunit.c
>@@ -101,6 +101,9 @@ static void hpcc_test_compare_value_boundaries(struct kunit *test)
> 	percpu_counter_tree_set(&pct, 0);
> 	percpu_counter_tree_approximate_accuracy_range(&pct, &under, &over);
> 
>+	if (!under && !over)
>+		kunit_skip(test, "no approximation accuracy on single-CPU topology");
>+
> 	/*
> 	 * With approx_sum = precise_sum = 0, from the accuracy invariant:
> 	 *   approx_sum - over <= precise_sum <= approx_sum + under
>@@ -214,6 +217,9 @@ static void hpcc_test_compare_counter_boundaries(struct kunit *test)
> 	 */
> 	combined = under + over;
> 
>+	if (!combined)
>+		kunit_skip(test, "no approximation accuracy on single-CPU topology");
>+
> 	/* --- percpu_counter_tree_approximate_compare --- */
> 
> 	/* At boundary: indeterminate */




Keep it up!
Have a great day!

Reviewed-by: Josh Law <objecting@objecting.org>


V/R


Josh Law
Re: [PATCH] lib: skip percpu_counter_tree boundary kunit tests on single-CPU
Posted by Mathieu Desnoyers 2 weeks, 6 days ago 
On 2026-03-17 11:06, David Carlier wrote:
> On single-CPU topologies, accuracy_multiplier is zero, making both
> approx_accuracy_range.under and .over zero. The boundary tests in
> hpcc_test_compare_value_boundaries and hpcc_test_compare_counter_boundaries
> then degenerate to comparing 0 vs 0, which correctly returns 0 (equal)
> but the tests expect nonzero results.
> 
> Skip these boundary tests with kunit_skip() when accuracy is zero,
> since approximation boundaries are meaningless without multi-CPU carry
> propagation.

AFAIU kunit_skip is implemented with kunit_try_catch_throw, which aborts
the specific test function. The placement of those kunit_skip appears to
leak memory allocated with kzalloc(). Am I missing something ?

Thanks,

Mathieu

> 
> Fixes: ebc1ff504f55 ("lib: add kunit boundary tests for percpu_counter_tree comparisons")
> Signed-off-by: David Carlier <devnexen@gmail.com>
> ---
>   lib/tests/percpu_counter_tree_kunit.c | 6 ++++++
>   1 file changed, 6 insertions(+)
> 
> diff --git a/lib/tests/percpu_counter_tree_kunit.c b/lib/tests/percpu_counter_tree_kunit.c
> index 4d058bc78f7d..609992bfaa21 100644
> --- a/lib/tests/percpu_counter_tree_kunit.c
> +++ b/lib/tests/percpu_counter_tree_kunit.c
> @@ -101,6 +101,9 @@ static void hpcc_test_compare_value_boundaries(struct kunit *test)
>   	percpu_counter_tree_set(&pct, 0);
>   	percpu_counter_tree_approximate_accuracy_range(&pct, &under, &over);
>   
> +	if (!under && !over)
> +		kunit_skip(test, "no approximation accuracy on single-CPU topology");
> +
>   	/*
>   	 * With approx_sum = precise_sum = 0, from the accuracy invariant:
>   	 *   approx_sum - over <= precise_sum <= approx_sum + under
> @@ -214,6 +217,9 @@ static void hpcc_test_compare_counter_boundaries(struct kunit *test)
>   	 */
>   	combined = under + over;
>   
> +	if (!combined)
> +		kunit_skip(test, "no approximation accuracy on single-CPU topology");
> +
>   	/* --- percpu_counter_tree_approximate_compare --- */
>   
>   	/* At boundary: indeterminate */


-- 
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com
[PATCH] lib: skip percpu_counter_tree boundary kunit tests on single-CPU
Posted by David Carlier 2 weeks, 6 days ago 
On single-CPU topologies, accuracy_multiplier is zero, making both
approx_accuracy_range.under and .over zero. The boundary tests in
hpcc_test_compare_value_boundaries and hpcc_test_compare_counter_boundaries
then degenerate to comparing 0 vs 0, which correctly returns 0 (equal)
but the tests expect nonzero results.

Skip these boundary tests with kunit_skip() when accuracy is zero,
since approximation boundaries are meaningless without multi-CPU carry
propagation. Use percpu_counter_tree_items_size() as the topology check
before any allocations to avoid leaking memory on skip.

Fixes: ebc1ff504f55 ("lib: add kunit boundary tests for percpu_counter_tree comparisons")
Signed-off-by: David Carlier <devnexen@gmail.com>
---
 lib/tests/percpu_counter_tree_kunit.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/lib/tests/percpu_counter_tree_kunit.c b/lib/tests/percpu_counter_tree_kunit.c
index 4d058bc78f7d..b773d20867d4 100644
--- a/lib/tests/percpu_counter_tree_kunit.c
+++ b/lib/tests/percpu_counter_tree_kunit.c
@@ -93,6 +93,9 @@ static void hpcc_test_compare_value_boundaries(struct kunit *test)
 	unsigned long under = 0, over = 0;
 	int ret;
 
+	if (!percpu_counter_tree_items_size())
+		kunit_skip(test, "no approximation accuracy on single-CPU topology");
+
 	counter_items = kzalloc(percpu_counter_tree_items_size(), GFP_KERNEL);
 	KUNIT_ASSERT_PTR_NE(test, counter_items, NULL);
 	ret = percpu_counter_tree_init(&pct, counter_items, 32, GFP_KERNEL);
@@ -197,6 +200,9 @@ static void hpcc_test_compare_counter_boundaries(struct kunit *test)
 	unsigned long combined;
 	int ret;
 
+	if (!percpu_counter_tree_items_size())
+		kunit_skip(test, "no approximation accuracy on single-CPU topology");
+
 	counter_items = kzalloc(percpu_counter_tree_items_size() * 2,
 				GFP_KERNEL);
 	KUNIT_ASSERT_PTR_NE(test, counter_items, NULL);
-- 
2.53.0
Re: [PATCH] lib: skip percpu_counter_tree boundary kunit tests on single-CPU
Posted by Mark Brown 2 weeks, 6 days ago 
On Tue, Mar 17, 2026 at 03:39:15PM +0000, David Carlier wrote:
> On single-CPU topologies, accuracy_multiplier is zero, making both
> approx_accuracy_range.under and .over zero. The boundary tests in
> hpcc_test_compare_value_boundaries and hpcc_test_compare_counter_boundaries
> then degenerate to comparing 0 vs 0, which correctly returns 0 (equal)
> but the tests expect nonzero results.
> 
> Skip these boundary tests with kunit_skip() when accuracy is zero,
> since approximation boundaries are meaningless without multi-CPU carry
> propagation. Use percpu_counter_tree_items_size() as the topology check
> before any allocations to avoid leaking memory on skip.

Reviewed-by: Mark Brown <broonie@kernel.org>

Thanks!
Re: [PATCH] lib: skip percpu_counter_tree boundary kunit tests on single-CPU
Posted by Mathieu Desnoyers 2 weeks, 6 days ago 
On 2026-03-17 11:39, David Carlier wrote:
> On single-CPU topologies, accuracy_multiplier is zero, making both
> approx_accuracy_range.under and .over zero. The boundary tests in
> hpcc_test_compare_value_boundaries and hpcc_test_compare_counter_boundaries
> then degenerate to comparing 0 vs 0, which correctly returns 0 (equal)
> but the tests expect nonzero results.
> 
> Skip these boundary tests with kunit_skip() when accuracy is zero,
> since approximation boundaries are meaningless without multi-CPU carry
> propagation. Use percpu_counter_tree_items_size() as the topology check
> before any allocations to avoid leaking memory on skip.
> 
> Fixes: ebc1ff504f55 ("lib: add kunit boundary tests for percpu_counter_tree comparisons")
> Signed-off-by: David Carlier <devnexen@gmail.com>

Thanks!

Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

> ---
>   lib/tests/percpu_counter_tree_kunit.c | 6 ++++++
>   1 file changed, 6 insertions(+)
> 
> diff --git a/lib/tests/percpu_counter_tree_kunit.c b/lib/tests/percpu_counter_tree_kunit.c
> index 4d058bc78f7d..b773d20867d4 100644
> --- a/lib/tests/percpu_counter_tree_kunit.c
> +++ b/lib/tests/percpu_counter_tree_kunit.c
> @@ -93,6 +93,9 @@ static void hpcc_test_compare_value_boundaries(struct kunit *test)
>   	unsigned long under = 0, over = 0;
>   	int ret;
>   
> +	if (!percpu_counter_tree_items_size())
> +		kunit_skip(test, "no approximation accuracy on single-CPU topology");
> +
>   	counter_items = kzalloc(percpu_counter_tree_items_size(), GFP_KERNEL);
>   	KUNIT_ASSERT_PTR_NE(test, counter_items, NULL);
>   	ret = percpu_counter_tree_init(&pct, counter_items, 32, GFP_KERNEL);
> @@ -197,6 +200,9 @@ static void hpcc_test_compare_counter_boundaries(struct kunit *test)
>   	unsigned long combined;
>   	int ret;
>   
> +	if (!percpu_counter_tree_items_size())
> +		kunit_skip(test, "no approximation accuracy on single-CPU topology");
> +
>   	counter_items = kzalloc(percpu_counter_tree_items_size() * 2,
>   				GFP_KERNEL);
>   	KUNIT_ASSERT_PTR_NE(test, counter_items, NULL);


-- 
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com

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