sched_ext: Maintain an online cid mask in the scheduler arenagrafted

Schedulers on the default cid mapping treat [0, nr_online_cids) as the
online set and restart on hotplug. Schedulers that install their own mapping
with scx_bpf_cid_override() have no way to learn which cids are online: the
count no longer identifies members and the CPU-form cpumask is unusable from
cid programs. This is an obvious hole in the cid API.

Add scx_bpf_online_cmask(), a kernel-maintained cmask in the scheduler's
arena, allocated alongside the per-CPU scratch masks and populated after the
cid mapping is finalized and before ops.init(), for child schedulers too.
The pointer stays valid through ops.exit() with no reference to take. It is
the arena offset as a void pointer, the same form struct_ops arena arguments
arrive in. The verifier types the void return as a scalar for the program's
arena cast.

The mask follows the SCX hotplug notifications: seeded from cpu_active_mask
and updated before ops.cid_online/offline() runs, so it lags cpu_online_mask
only inside a hotplug transition. Updates walk the scheduler list under the
lock that also serializes unlinking. Reads are live, not atomic snapshots.
Root initialization excludes hotplug.

v2: Reworded the getter kerneldoc (Andrea Righi).

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

1 files changed, 474 insertions, 0 deletions

diff --git a/lib/kunit/attributes.c b/lib/kunit/attributes.c
new file mode 100644
index 000000000..6d7a53af9
--- /dev/null
+++ b/lib/kunit/attributes.c
@@ -0,0 +1,474 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KUnit API to save and access test attributes
+ *
+ * Copyright (C) 2023, Google LLC.
+ * Author: Rae Moar <rmoar@google.com>
+ */
+
+#include <kunit/test.h>
+#include <kunit/attributes.h>
+
+/* Options for printing attributes:
+ * PRINT_ALWAYS - attribute is printed for every test case and suite if set
+ * PRINT_SUITE - attribute is printed for every suite if set but not for test cases
+ * PRINT_NEVER - attribute is never printed
+ */
+enum print_ops {
+	PRINT_ALWAYS,
+	PRINT_SUITE,
+	PRINT_NEVER,
+};
+
+/**
+ * struct kunit_attr - represents a test attribute and holds flexible
+ * helper functions to interact with attribute.
+ *
+ * @name: name of test attribute, eg. speed
+ * @get_attr: function to return attribute value given a test
+ * @to_string: function to return string representation of given
+ * attribute value
+ * @filter: function to indicate whether a given attribute value passes a
+ * filter
+ * @attr_default: default attribute value used during filtering
+ * @print: value of enum print_ops to indicate when to print attribute
+ */
+struct kunit_attr {
+	const char *name;
+	void *(*get_attr)(void *test_or_suite, bool is_test);
+	const char *(*to_string)(void *attr, bool *to_free);
+	int (*filter)(void *attr, const char *input, int *err);
+	void *attr_default;
+	enum print_ops print;
+};
+
+/* String Lists for enum Attributes */
+
+static const char * const speed_str_list[] = {"unset", "very_slow", "slow", "normal"};
+
+/* To String Methods */
+
+static const char *attr_enum_to_string(void *attr, const char * const str_list[], bool *to_free)
+{
+	long val = (long)attr;
+
+	*to_free = false;
+	if (!val)
+		return NULL;
+	return str_list[val];
+}
+
+static const char *attr_bool_to_string(void *attr, bool *to_free)
+{
+	bool val = (bool)attr;
+
+	*to_free = false;
+	if (val)
+		return "true";
+	return "false";
+}
+
+static const char *attr_speed_to_string(void *attr, bool *to_free)
+{
+	return attr_enum_to_string(attr, speed_str_list, to_free);
+}
+
+static const char *attr_string_to_string(void *attr, bool *to_free)
+{
+	*to_free = false;
+	return (char *) attr;
+}
+
+/* Filter Methods */
+
+static const char op_list[] = "<>!=";
+
+/*
+ * Returns whether the inputted integer value matches the filter given
+ * by the operation string and inputted integer.
+ */
+static int int_filter(long val, const char *op, int input, int *err)
+{
+	if (!strncmp(op, "<=", 2))
+		return (val <= input);
+	else if (!strncmp(op, ">=", 2))
+		return (val >= input);
+	else if (!strncmp(op, "!=", 2))
+		return (val != input);
+	else if (!strncmp(op, ">", 1))
+		return (val > input);
+	else if (!strncmp(op, "<", 1))
+		return (val < input);
+	else if (!strncmp(op, "=", 1))
+		return (val == input);
+	*err = -EINVAL;
+	pr_err("kunit executor: invalid filter operation: %s\n", op);
+	return false;
+}
+
+/*
+ * Returns whether the inputted enum value "attr" matches the filter given
+ * by the input string. Note: the str_list includes the corresponding string
+ * list to the enum values.
+ */
+static int attr_enum_filter(void *attr, const char *input, int *err,
+		const char * const str_list[], int max)
+{
+	int i, j, input_int = -1;
+	long test_val = (long)attr;
+	const char *input_val = NULL;
+
+	for (i = 0; input[i]; i++) {
+		if (!strchr(op_list, input[i])) {
+			input_val = input + i;
+			break;
+		}
+	}
+
+	if (!input_val) {
+		*err = -EINVAL;
+		pr_err("kunit executor: filter value not found: %s\n", input);
+		return false;
+	}
+
+	for (j = 0; j <= max; j++) {
+		if (!strcmp(input_val, str_list[j]))
+			input_int = j;
+	}
+
+	if (input_int < 0) {
+		*err = -EINVAL;
+		pr_err("kunit executor: invalid filter input: %s\n", input);
+		return false;
+	}
+
+	return int_filter(test_val, input, input_int, err);
+}
+
+static int attr_speed_filter(void *attr, const char *input, int *err)
+{
+	return attr_enum_filter(attr, input, err, speed_str_list, KUNIT_SPEED_MAX);
+}
+
+/*
+ * Returns whether the inputted string value (attr) matches the filter given
+ * by the input string.
+ */
+static int attr_string_filter(void *attr, const char *input, int *err)
+{
+	char *str = attr;
+
+	if (!strncmp(input, "<", 1)) {
+		*err = -EINVAL;
+		pr_err("kunit executor: invalid filter input: %s\n", input);
+		return false;
+	} else if (!strncmp(input, ">", 1)) {
+		*err = -EINVAL;
+		pr_err("kunit executor: invalid filter input: %s\n", input);
+		return false;
+	} else if (!strncmp(input, "!=", 2)) {
+		return (strcmp(input + 2, str) != 0);
+	} else if (!strncmp(input, "=", 1)) {
+		return (strcmp(input + 1, str) == 0);
+	}
+	*err = -EINVAL;
+	pr_err("kunit executor: invalid filter operation: %s\n", input);
+	return false;
+}
+
+static int attr_bool_filter(void *attr, const char *input, int *err)
+{
+	int i, input_int = -1;
+	long val = (long)attr;
+	const char *input_str = NULL;
+
+	for (i = 0; input[i]; i++) {
+		if (!strchr(op_list, input[i])) {
+			input_str = input + i;
+			break;
+		}
+	}
+
+	if (!input_str) {
+		*err = -EINVAL;
+		pr_err("kunit executor: filter value not found: %s\n", input);
+		return false;
+	}
+
+	if (!strcmp(input_str, "true"))
+		input_int = (int)true;
+	else if (!strcmp(input_str, "false"))
+		input_int = (int)false;
+	else {
+		*err = -EINVAL;
+		pr_err("kunit executor: invalid filter input: %s\n", input);
+		return false;
+	}
+
+	return int_filter(val, input, input_int, err);
+}
+
+/* Get Attribute Methods */
+
+static void *attr_speed_get(void *test_or_suite, bool is_test)
+{
+	struct kunit_suite *suite = is_test ? NULL : test_or_suite;
+	struct kunit_case *test = is_test ? test_or_suite : NULL;
+
+	if (test)
+		return ((void *) test->attr.speed);
+	else
+		return ((void *) suite->attr.speed);
+}
+
+static void *attr_module_get(void *test_or_suite, bool is_test)
+{
+	struct kunit_suite *suite = is_test ? NULL : test_or_suite;
+	struct kunit_case *test = is_test ? test_or_suite : NULL;
+
+	// Suites get their module attribute from their first test_case
+	if (test)
+		return ((void *) test->module_name);
+	else if (kunit_suite_num_test_cases(suite) > 0)
+		return ((void *) suite->test_cases[0].module_name);
+	else
+		return (void *) "";
+}
+
+static void *attr_is_init_get(void *test_or_suite, bool is_test)
+{
+	struct kunit_suite *suite = is_test ? NULL : test_or_suite;
+	struct kunit_case *test = is_test ? test_or_suite : NULL;
+
+	if (test)
+		return ((void *) NULL);
+	else
+		return ((void *) suite->is_init);
+}
+
+/* List of all Test Attributes */
+
+static struct kunit_attr kunit_attr_list[] = {
+	{
+		.name = "speed",
+		.get_attr = attr_speed_get,
+		.to_string = attr_speed_to_string,
+		.filter = attr_speed_filter,
+		.attr_default = (void *)KUNIT_SPEED_NORMAL,
+		.print = PRINT_ALWAYS,
+	},
+	{
+		.name = "module",
+		.get_attr = attr_module_get,
+		.to_string = attr_string_to_string,
+		.filter = attr_string_filter,
+		.attr_default = (void *)"",
+		.print = PRINT_SUITE,
+	},
+	{
+		.name = "is_init",
+		.get_attr = attr_is_init_get,
+		.to_string = attr_bool_to_string,
+		.filter = attr_bool_filter,
+		.attr_default = (void *)false,
+		.print = PRINT_SUITE,
+	}
+};
+
+/* Helper Functions to Access Attributes */
+
+const char *kunit_attr_filter_name(struct kunit_attr_filter filter)
+{
+	return filter.attr->name;
+}
+
+void kunit_print_attr(void *test_or_suite, bool is_test, unsigned int test_level)
+{
+	int i;
+	bool to_free = false;
+	void *attr;
+	const char *attr_name, *attr_str;
+	struct kunit_suite *suite = is_test ? NULL : test_or_suite;
+	struct kunit_case *test = is_test ? test_or_suite : NULL;
+
+	for (i = 0; i < ARRAY_SIZE(kunit_attr_list); i++) {
+		if (kunit_attr_list[i].print == PRINT_NEVER ||
+				(test && kunit_attr_list[i].print == PRINT_SUITE))
+			continue;
+		attr = kunit_attr_list[i].get_attr(test_or_suite, is_test);
+		if (attr) {
+			attr_name = kunit_attr_list[i].name;
+			attr_str = kunit_attr_list[i].to_string(attr, &to_free);
+			if (test) {
+				kunit_log(KERN_INFO, test, "%*s# %s.%s: %s",
+					KUNIT_INDENT_LEN * test_level, "", test->name,
+					attr_name, attr_str);
+			} else {
+				kunit_log(KERN_INFO, suite, "%*s# %s: %s",
+					KUNIT_INDENT_LEN * test_level, "", attr_name, attr_str);
+			}
+
+			/* Free to_string of attribute if needed */
+			if (to_free)
+				kfree(attr_str);
+		}
+	}
+}
+
+/* Helper Functions to Filter Attributes */
+
+int kunit_get_filter_count(char *input)
+{
+	int i, comma_index = 0, count = 0;
+
+	for (i = 0; input[i]; i++) {
+		if (input[i] == ',') {
+			if ((i - comma_index) > 1)
+				count++;
+			comma_index = i;
+		}
+	}
+	if ((i - comma_index) > 0)
+		count++;
+	return count;
+}
+
+struct kunit_attr_filter kunit_next_attr_filter(char **filters, int *err)
+{
+	struct kunit_attr_filter filter = {};
+	int i, j, comma_index = 0, new_start_index = 0;
+	int op_index = -1, attr_index = -1;
+	char op;
+	char *input = *filters;
+
+	/* Parse input until operation */
+	for (i = 0; input[i]; i++) {
+		if (op_index < 0 && strchr(op_list, input[i])) {
+			op_index = i;
+		} else if (!comma_index && input[i] == ',') {
+			comma_index = i;
+		} else if (comma_index && input[i] != ' ') {
+			new_start_index = i;
+			break;
+		}
+	}
+
+	if (op_index <= 0) {
+		*err = -EINVAL;
+		pr_err("kunit executor: filter operation not found: %s\n", input);
+		return filter;
+	}
+
+	/* Temporarily set operator to \0 character. */
+	op = input[op_index];
+	input[op_index] = '\0';
+
+	/* Find associated kunit_attr object */
+	for (j = 0; j < ARRAY_SIZE(kunit_attr_list); j++) {
+		if (!strcmp(input, kunit_attr_list[j].name)) {
+			attr_index = j;
+			break;
+		}
+	}
+
+	input[op_index] = op;
+
+	if (attr_index < 0) {
+		*err = -EINVAL;
+		pr_err("kunit executor: attribute not found: %s\n", input);
+	} else {
+		filter.attr = &kunit_attr_list[attr_index];
+	}
+
+	if (comma_index > 0) {
+		input[comma_index] = '\0';
+		filter.input = input + op_index;
+		input = input + new_start_index;
+	} else {
+		filter.input = input + op_index;
+		input = NULL;
+	}
+
+	*filters = input;
+
+	return filter;
+}
+
+struct kunit_suite *kunit_filter_attr_tests(const struct kunit_suite *const suite,
+		struct kunit_attr_filter filter, char *action, int *err)
+{
+	int n = 0;
+	struct kunit_case *filtered, *test_case;
+	struct kunit_suite *copy;
+	void *suite_val, *test_val;
+	bool suite_result, test_result, default_result, result;
+
+	/* Allocate memory for new copy of suite and list of test cases */
+	copy = kmemdup(suite, sizeof(*copy), GFP_KERNEL);
+	if (!copy)
+		return ERR_PTR(-ENOMEM);
+
+	kunit_suite_for_each_test_case(suite, test_case) { n++; }
+
+	filtered = kzalloc_objs(*filtered, n + 1);
+	if (!filtered) {
+		kfree(copy);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	n = 0;
+
+	/* Save filtering result on default value */
+	default_result = filter.attr->filter(filter.attr->attr_default, filter.input, err);
+	if (*err)
+		goto err;
+
+	/* Save suite attribute value and filtering result on that value */
+	suite_val = filter.attr->get_attr((void *)suite, false);
+	suite_result = filter.attr->filter(suite_val, filter.input, err);
+	if (*err)
+		goto err;
+
+	/* For each test case, save test case if passes filtering. */
+	kunit_suite_for_each_test_case(suite, test_case) {
+		test_val = filter.attr->get_attr((void *) test_case, true);
+		test_result = filter.attr->filter(filter.attr->get_attr(test_case, true),
+				filter.input, err);
+		if (*err)
+			goto err;
+
+		/*
+		 * If attribute value of test case is set, filter on that value.
+		 * If not, filter on suite value if set. If not, filter on
+		 * default value.
+		 */
+		result = false;
+		if (test_val) {
+			if (test_result)
+				result = true;
+		} else if (suite_val) {
+			if (suite_result)
+				result = true;
+		} else if (default_result) {
+			result = true;
+		}
+
+		if (result) {
+			filtered[n++] = *test_case;
+		} else if (action && strcmp(action, "skip") == 0) {
+			test_case->status = KUNIT_SKIPPED;
+			filtered[n++] = *test_case;
+		}
+	}
+
+err:
+	if (n == 0 || *err) {
+		kfree(copy);
+		kfree(filtered);
+		return NULL;
+	}
+
+	copy->test_cases = filtered;
+
+	return copy;
+}