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, 232 insertions, 0 deletions

diff --git a/include/kunit/assert.h b/include/kunit/assert.h
new file mode 100644
index 000000000..bb879389f
--- /dev/null
+++ b/include/kunit/assert.h
@@ -0,0 +1,232 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Assertion and expectation serialization API.
+ *
+ * Copyright (C) 2019, Google LLC.
+ * Author: Brendan Higgins <brendanhiggins@google.com>
+ */
+
+#ifndef _KUNIT_ASSERT_H
+#define _KUNIT_ASSERT_H
+
+#include <linux/err.h>
+#include <linux/printk.h>
+
+struct kunit;
+struct string_stream;
+
+/**
+ * enum kunit_assert_type - Type of expectation/assertion.
+ * @KUNIT_ASSERTION: Used to denote that a kunit_assert represents an assertion.
+ * @KUNIT_EXPECTATION: Denotes that a kunit_assert represents an expectation.
+ *
+ * Used in conjunction with a &struct kunit_assert to denote whether it
+ * represents an expectation or an assertion.
+ */
+enum kunit_assert_type {
+	KUNIT_ASSERTION,
+	KUNIT_EXPECTATION,
+};
+
+/**
+ * struct kunit_loc - Identifies the source location of a line of code.
+ * @line: the line number in the file.
+ * @file: the file name.
+ */
+struct kunit_loc {
+	int line;
+	const char *file;
+};
+
+#define KUNIT_CURRENT_LOC { .file = __FILE__, .line = __LINE__ }
+
+/**
+ * struct kunit_assert - Data for printing a failed assertion or expectation.
+ *
+ * Represents a failed expectation/assertion. Contains all the data necessary to
+ * format a string to a user reporting the failure.
+ */
+struct kunit_assert {};
+
+typedef void (*assert_format_t)(const struct kunit_assert *assert,
+				const struct va_format *message,
+				struct string_stream *stream);
+
+void kunit_assert_prologue(const struct kunit_loc *loc,
+			   enum kunit_assert_type type,
+			   struct string_stream *stream);
+
+/**
+ * struct kunit_fail_assert - Represents a plain fail expectation/assertion.
+ * @assert: The parent of this type.
+ *
+ * Represents a simple KUNIT_FAIL/KUNIT_FAIL_AND_ABORT that always fails.
+ */
+struct kunit_fail_assert {
+	struct kunit_assert assert;
+};
+
+void kunit_fail_assert_format(const struct kunit_assert *assert,
+			      const struct va_format *message,
+			      struct string_stream *stream);
+
+/**
+ * struct kunit_unary_assert - Represents a KUNIT_{EXPECT|ASSERT}_{TRUE|FALSE}
+ * @assert: The parent of this type.
+ * @condition: A string representation of a conditional expression.
+ * @expected_true: True if of type KUNIT_{EXPECT|ASSERT}_TRUE, false otherwise.
+ *
+ * Represents a simple expectation or assertion that simply asserts something is
+ * true or false. In other words, represents the expectations:
+ * KUNIT_{EXPECT|ASSERT}_{TRUE|FALSE}
+ */
+struct kunit_unary_assert {
+	struct kunit_assert assert;
+	const char *condition;
+	bool expected_true;
+};
+
+void kunit_unary_assert_format(const struct kunit_assert *assert,
+			       const struct va_format *message,
+			       struct string_stream *stream);
+
+/**
+ * struct kunit_ptr_not_err_assert - An expectation/assertion that a pointer is
+ *	not NULL and not a -errno.
+ * @assert: The parent of this type.
+ * @text: A string representation of the expression passed to the expectation.
+ * @value: The actual evaluated pointer value of the expression.
+ *
+ * Represents an expectation/assertion that a pointer is not null and is does
+ * not contain a -errno. (See IS_ERR_OR_NULL().)
+ */
+struct kunit_ptr_not_err_assert {
+	struct kunit_assert assert;
+	const char *text;
+	const void *value;
+};
+
+void kunit_ptr_not_err_assert_format(const struct kunit_assert *assert,
+				     const struct va_format *message,
+				     struct string_stream *stream);
+
+/**
+ * struct kunit_binary_assert_text - holds strings for &struct
+ *	kunit_binary_assert and friends to try and make the structs smaller.
+ * @operation: A string representation of the comparison operator (e.g. "==").
+ * @left_text: A string representation of the left expression (e.g. "2+2").
+ * @right_text: A string representation of the right expression (e.g. "2+2").
+ */
+struct kunit_binary_assert_text {
+	const char *operation;
+	const char *left_text;
+	const char *right_text;
+};
+
+/**
+ * struct kunit_binary_assert - An expectation/assertion that compares two
+ *	non-pointer values (for example, KUNIT_EXPECT_EQ(test, 1 + 1, 2)).
+ * @assert: The parent of this type.
+ * @text: Holds the textual representations of the operands and op (e.g.  "==").
+ * @left_value: The actual evaluated value of the expression in the left slot.
+ * @right_value: The actual evaluated value of the expression in the right slot.
+ *
+ * Represents an expectation/assertion that compares two non-pointer values. For
+ * example, to expect that 1 + 1 == 2, you can use the expectation
+ * KUNIT_EXPECT_EQ(test, 1 + 1, 2);
+ */
+struct kunit_binary_assert {
+	struct kunit_assert assert;
+	const struct kunit_binary_assert_text *text;
+	long long left_value;
+	long long right_value;
+};
+
+void kunit_binary_assert_format(const struct kunit_assert *assert,
+				const struct va_format *message,
+				struct string_stream *stream);
+
+/**
+ * struct kunit_binary_ptr_assert - An expectation/assertion that compares two
+ *	pointer values (for example, KUNIT_EXPECT_PTR_EQ(test, foo, bar)).
+ * @assert: The parent of this type.
+ * @text: Holds the textual representations of the operands and op (e.g.  "==").
+ * @left_value: The actual evaluated value of the expression in the left slot.
+ * @right_value: The actual evaluated value of the expression in the right slot.
+ *
+ * Represents an expectation/assertion that compares two pointer values. For
+ * example, to expect that foo and bar point to the same thing, you can use the
+ * expectation KUNIT_EXPECT_PTR_EQ(test, foo, bar);
+ */
+struct kunit_binary_ptr_assert {
+	struct kunit_assert assert;
+	const struct kunit_binary_assert_text *text;
+	const void *left_value;
+	const void *right_value;
+};
+
+void kunit_binary_ptr_assert_format(const struct kunit_assert *assert,
+				    const struct va_format *message,
+				    struct string_stream *stream);
+
+/**
+ * struct kunit_binary_str_assert - An expectation/assertion that compares two
+ *	string values (for example, KUNIT_EXPECT_STREQ(test, foo, "bar")).
+ * @assert: The parent of this type.
+ * @text: Holds the textual representations of the operands and comparator.
+ * @left_value: The actual evaluated value of the expression in the left slot.
+ * @right_value: The actual evaluated value of the expression in the right slot.
+ *
+ * Represents an expectation/assertion that compares two string values. For
+ * example, to expect that the string in foo is equal to "bar", you can use the
+ * expectation KUNIT_EXPECT_STREQ(test, foo, "bar");
+ */
+struct kunit_binary_str_assert {
+	struct kunit_assert assert;
+	const struct kunit_binary_assert_text *text;
+	const char *left_value;
+	const char *right_value;
+};
+
+void kunit_binary_str_assert_format(const struct kunit_assert *assert,
+				    const struct va_format *message,
+				    struct string_stream *stream);
+
+/**
+ * struct kunit_mem_assert - An expectation/assertion that compares two
+ *	memory blocks.
+ * @assert: The parent of this type.
+ * @text: Holds the textual representations of the operands and comparator.
+ * @left_value: The actual evaluated value of the expression in the left slot.
+ * @right_value: The actual evaluated value of the expression in the right slot.
+ * @size: Size of the memory block analysed in bytes.
+ *
+ * Represents an expectation/assertion that compares two memory blocks. For
+ * example, to expect that the first three bytes of foo is equal to the
+ * first three bytes of bar, you can use the expectation
+ * KUNIT_EXPECT_MEMEQ(test, foo, bar, 3);
+ */
+struct kunit_mem_assert {
+	struct kunit_assert assert;
+	const struct kunit_binary_assert_text *text;
+	const void *left_value;
+	const void *right_value;
+	const size_t size;
+};
+
+void kunit_mem_assert_format(const struct kunit_assert *assert,
+			     const struct va_format *message,
+			     struct string_stream *stream);
+
+#if IS_ENABLED(CONFIG_KUNIT)
+void kunit_assert_print_msg(const struct va_format *message,
+			    struct string_stream *stream);
+bool is_literal(const char *text, long long value);
+bool is_str_literal(const char *text, const char *value);
+void kunit_assert_hexdump(struct string_stream *stream,
+			  const void *buf,
+			  const void *compared_buf,
+			  const size_t len);
+#endif
+
+#endif /*  _KUNIT_ASSERT_H */