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>

46 files changed, 190 insertions, 0 deletions

diff --git a/tools/bootconfig/samples/bad-array-after-comment.bconf b/tools/bootconfig/samples/bad-array-after-comment.bconf
new file mode 100644
index 000000000..fdb6d4e04
--- /dev/null
+++ b/tools/bootconfig/samples/bad-array-after-comment.bconf
@@ -0,0 +1,4 @@
+# the first array value must be on the same line as the key
+key = # comment
+ value1,
+ value2
diff --git a/tools/bootconfig/samples/bad-array-in-next-line.bconf b/tools/bootconfig/samples/bad-array-in-next-line.bconf
new file mode 100644
index 000000000..95a99a3bd
--- /dev/null
+++ b/tools/bootconfig/samples/bad-array-in-next-line.bconf
@@ -0,0 +1,4 @@
+# the first array value must be on the same line as the key
+key =
+  value1,
+  value2
diff --git a/tools/bootconfig/samples/bad-array-space-comment.bconf b/tools/bootconfig/samples/bad-array-space-comment.bconf
new file mode 100644
index 000000000..fda19e47d
--- /dev/null
+++ b/tools/bootconfig/samples/bad-array-space-comment.bconf
@@ -0,0 +1,5 @@
+key =	# comment
+	"value1",	  # comment1
+	"value2" 	  # comment2
+,
+	"value3"
diff --git a/tools/bootconfig/samples/bad-array.bconf b/tools/bootconfig/samples/bad-array.bconf
new file mode 100644
index 000000000..0174af019
--- /dev/null
+++ b/tools/bootconfig/samples/bad-array.bconf
@@ -0,0 +1,2 @@
+# Array must be comma separated.
+key = "value1" "value2"
diff --git a/tools/bootconfig/samples/bad-dotword.bconf b/tools/bootconfig/samples/bad-dotword.bconf
new file mode 100644
index 000000000..ba5557b2b
--- /dev/null
+++ b/tools/bootconfig/samples/bad-dotword.bconf
@@ -0,0 +1,4 @@
+# do not start keyword with .
+key {
+  .word = 1
+}
diff --git a/tools/bootconfig/samples/bad-empty.bconf b/tools/bootconfig/samples/bad-empty.bconf
new file mode 100644
index 000000000..2ba3f6cc6
--- /dev/null
+++ b/tools/bootconfig/samples/bad-empty.bconf
@@ -0,0 +1 @@
+# Wrong boot config: comment only
diff --git a/tools/bootconfig/samples/bad-keyerror.bconf b/tools/bootconfig/samples/bad-keyerror.bconf
new file mode 100644
index 000000000..b6e247a09
--- /dev/null
+++ b/tools/bootconfig/samples/bad-keyerror.bconf
@@ -0,0 +1,2 @@
+# key word can not contain ","
+key,word
diff --git a/tools/bootconfig/samples/bad-longkey.bconf b/tools/bootconfig/samples/bad-longkey.bconf
new file mode 100644
index 000000000..eb97369f9
--- /dev/null
+++ b/tools/bootconfig/samples/bad-longkey.bconf
@@ -0,0 +1 @@
+key_word_is_too_long01234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345
diff --git a/tools/bootconfig/samples/bad-manywords.bconf b/tools/bootconfig/samples/bad-manywords.bconf
new file mode 100644
index 000000000..8db81967c
--- /dev/null
+++ b/tools/bootconfig/samples/bad-manywords.bconf
@@ -0,0 +1 @@
+key1.is2.too3.long4.5.6.7.8.9.10.11.12.13.14.15.16.17
diff --git a/tools/bootconfig/samples/bad-no-keyword.bconf b/tools/bootconfig/samples/bad-no-keyword.bconf
new file mode 100644
index 000000000..eff268085
--- /dev/null
+++ b/tools/bootconfig/samples/bad-no-keyword.bconf
@@ -0,0 +1,2 @@
+# No keyword
+{}
diff --git a/tools/bootconfig/samples/bad-non-closed-brace.bconf b/tools/bootconfig/samples/bad-non-closed-brace.bconf
new file mode 100644
index 000000000..6ed9f3363
--- /dev/null
+++ b/tools/bootconfig/samples/bad-non-closed-brace.bconf
@@ -0,0 +1,4 @@
+foo {
+ bar {
+   buz
+ }
diff --git a/tools/bootconfig/samples/bad-nonprintable.bconf b/tools/bootconfig/samples/bad-nonprintable.bconf
new file mode 100644
index 000000000..3bb1a2864
--- /dev/null
+++ b/tools/bootconfig/samples/bad-nonprintable.bconf
@@ -0,0 +1,2 @@
+# Non printable
+key = ""
diff --git a/tools/bootconfig/samples/bad-over-max-brace.bconf b/tools/bootconfig/samples/bad-over-max-brace.bconf
new file mode 100644
index 000000000..74b5dc9e2
--- /dev/null
+++ b/tools/bootconfig/samples/bad-over-max-brace.bconf
@@ -0,0 +1,19 @@
+key1 {
+key2 {
+key3 {
+key4 {
+key5 {
+key6 {
+key7 {
+key8 {
+key9 {
+key10 {
+key11 {
+key12 {
+key13 {
+key14 {
+key15 {
+key16 {
+key17 {
+}}}}}}}}}}}}}}}}}
+
diff --git a/tools/bootconfig/samples/bad-samekey.bconf b/tools/bootconfig/samples/bad-samekey.bconf
new file mode 100644
index 000000000..e8d983a45
--- /dev/null
+++ b/tools/bootconfig/samples/bad-samekey.bconf
@@ -0,0 +1,6 @@
+# Same key value is not allowed
+key {
+	foo = value
+	bar = value2
+}
+key.foo = value
diff --git a/tools/bootconfig/samples/bad-spaceword.bconf b/tools/bootconfig/samples/bad-spaceword.bconf
new file mode 100644
index 000000000..90c703d32
--- /dev/null
+++ b/tools/bootconfig/samples/bad-spaceword.bconf
@@ -0,0 +1,2 @@
+# No space between words
+key . word
diff --git a/tools/bootconfig/samples/bad-tree.bconf b/tools/bootconfig/samples/bad-tree.bconf
new file mode 100644
index 000000000..5a6038edc
--- /dev/null
+++ b/tools/bootconfig/samples/bad-tree.bconf
@@ -0,0 +1,5 @@
+# brace is not closing
+tree {
+  node {
+    value = 1
+}
diff --git a/tools/bootconfig/samples/bad-value.bconf b/tools/bootconfig/samples/bad-value.bconf
new file mode 100644
index 000000000..a1217fed8
--- /dev/null
+++ b/tools/bootconfig/samples/bad-value.bconf
@@ -0,0 +1,3 @@
+# Quotes error
+value = "data
+
diff --git a/tools/bootconfig/samples/escaped.bconf b/tools/bootconfig/samples/escaped.bconf
new file mode 100644
index 000000000..9f72043b3
--- /dev/null
+++ b/tools/bootconfig/samples/escaped.bconf
@@ -0,0 +1,3 @@
+key1 = "A\B\C"
+key2 = '\'\''
+key3 = "\\"
diff --git a/tools/bootconfig/samples/exp-good-array-space-comment.bconf b/tools/bootconfig/samples/exp-good-array-space-comment.bconf
new file mode 100644
index 000000000..8d3278fa6
--- /dev/null
+++ b/tools/bootconfig/samples/exp-good-array-space-comment.bconf
@@ -0,0 +1 @@
+key = "value1", "value2", "value3";
diff --git a/tools/bootconfig/samples/exp-good-comment-after-value.bconf b/tools/bootconfig/samples/exp-good-comment-after-value.bconf
new file mode 100644
index 000000000..a8e8450db
--- /dev/null
+++ b/tools/bootconfig/samples/exp-good-comment-after-value.bconf
@@ -0,0 +1 @@
+key = "value";
diff --git a/tools/bootconfig/samples/exp-good-mixed-append.bconf b/tools/bootconfig/samples/exp-good-mixed-append.bconf
new file mode 100644
index 000000000..c2b407901
--- /dev/null
+++ b/tools/bootconfig/samples/exp-good-mixed-append.bconf
@@ -0,0 +1,2 @@
+key = "foo", "bar";
+keyx.subkey = "value";
diff --git a/tools/bootconfig/samples/exp-good-mixed-kv1.bconf b/tools/bootconfig/samples/exp-good-mixed-kv1.bconf
new file mode 100644
index 000000000..8346287d9
--- /dev/null
+++ b/tools/bootconfig/samples/exp-good-mixed-kv1.bconf
@@ -0,0 +1,2 @@
+key = "value";
+key.subkey = "another-value";
diff --git a/tools/bootconfig/samples/exp-good-mixed-kv2.bconf b/tools/bootconfig/samples/exp-good-mixed-kv2.bconf
new file mode 100644
index 000000000..40c6232c7
--- /dev/null
+++ b/tools/bootconfig/samples/exp-good-mixed-kv2.bconf
@@ -0,0 +1,2 @@
+key = "another-value";
+key.subkey = "value";
diff --git a/tools/bootconfig/samples/exp-good-mixed-kv3.bconf b/tools/bootconfig/samples/exp-good-mixed-kv3.bconf
new file mode 100644
index 000000000..8368a7bef
--- /dev/null
+++ b/tools/bootconfig/samples/exp-good-mixed-kv3.bconf
@@ -0,0 +1,5 @@
+key = "value";
+key {
+	subkey1;
+	subkey2 = "foo";
+}
diff --git a/tools/bootconfig/samples/exp-good-mixed-override.bconf b/tools/bootconfig/samples/exp-good-mixed-override.bconf
new file mode 100644
index 000000000..58757712c
--- /dev/null
+++ b/tools/bootconfig/samples/exp-good-mixed-override.bconf
@@ -0,0 +1,2 @@
+key = "value2";
+key.foo = "bar";
diff --git a/tools/bootconfig/samples/exp-good-nested-brace.bconf b/tools/bootconfig/samples/exp-good-nested-brace.bconf
new file mode 100644
index 000000000..19e0f51b4
--- /dev/null
+++ b/tools/bootconfig/samples/exp-good-nested-brace.bconf
@@ -0,0 +1 @@
+key1.key2.key3.key4.key5.key6.key7.key8.key9.key10.key11.key12.key13.key14.key15.key16;
diff --git a/tools/bootconfig/samples/exp-good-override.bconf b/tools/bootconfig/samples/exp-good-override.bconf
new file mode 100644
index 000000000..00bbd30e9
--- /dev/null
+++ b/tools/bootconfig/samples/exp-good-override.bconf
@@ -0,0 +1,4 @@
+key {
+	word = "2", "3";
+	new.word = "new";
+}
diff --git a/tools/bootconfig/samples/exp-good-printables.bconf b/tools/bootconfig/samples/exp-good-printables.bconf
new file mode 100644
index 000000000..5981d304e
--- /dev/null
+++ b/tools/bootconfig/samples/exp-good-printables.bconf
@@ -0,0 +1,2 @@
+key = "	
+ !#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~";
diff --git a/tools/bootconfig/samples/exp-good-simple.bconf b/tools/bootconfig/samples/exp-good-simple.bconf
new file mode 100644
index 000000000..d17f39421
--- /dev/null
+++ b/tools/bootconfig/samples/exp-good-simple.bconf
@@ -0,0 +1,8 @@
+key {
+	word1 = "1";
+	word2 = "2";
+	word3 = "3";
+	word4 = "4";
+	word5 = "5";
+	word6 = "6";
+}
diff --git a/tools/bootconfig/samples/exp-good-single.bconf b/tools/bootconfig/samples/exp-good-single.bconf
new file mode 100644
index 000000000..01196910d
--- /dev/null
+++ b/tools/bootconfig/samples/exp-good-single.bconf
@@ -0,0 +1,3 @@
+key = "1";
+key2 = "2";
+key3 = "alpha", "beta";
diff --git a/tools/bootconfig/samples/exp-good-space-after-value.bconf b/tools/bootconfig/samples/exp-good-space-after-value.bconf
new file mode 100644
index 000000000..a8e8450db
--- /dev/null
+++ b/tools/bootconfig/samples/exp-good-space-after-value.bconf
@@ -0,0 +1 @@
+key = "value";
diff --git a/tools/bootconfig/samples/exp-good-tree.bconf b/tools/bootconfig/samples/exp-good-tree.bconf
new file mode 100644
index 000000000..b711d38d8
--- /dev/null
+++ b/tools/bootconfig/samples/exp-good-tree.bconf
@@ -0,0 +1,8 @@
+key {
+	word.tree.value = "0";
+	word2.tree.value = "1", "2";
+}
+other.tree {
+	value = "2";
+	value2 = "3";
+}
diff --git a/tools/bootconfig/samples/good-array-space-comment.bconf b/tools/bootconfig/samples/good-array-space-comment.bconf
new file mode 100644
index 000000000..416fa2ed4
--- /dev/null
+++ b/tools/bootconfig/samples/good-array-space-comment.bconf
@@ -0,0 +1,3 @@
+key = "value1",	  # comment1
+	"value2"	 , # comment2
+	"value3"
diff --git a/tools/bootconfig/samples/good-comment-after-value.bconf b/tools/bootconfig/samples/good-comment-after-value.bconf
new file mode 100644
index 000000000..0d92a853d
--- /dev/null
+++ b/tools/bootconfig/samples/good-comment-after-value.bconf
@@ -0,0 +1 @@
+key = "value"  # comment
diff --git a/tools/bootconfig/samples/good-mixed-append.bconf b/tools/bootconfig/samples/good-mixed-append.bconf
new file mode 100644
index 000000000..b99a089a0
--- /dev/null
+++ b/tools/bootconfig/samples/good-mixed-append.bconf
@@ -0,0 +1,4 @@
+key = foo
+keyx.subkey = value
+key += bar
+
diff --git a/tools/bootconfig/samples/good-mixed-kv1.bconf b/tools/bootconfig/samples/good-mixed-kv1.bconf
new file mode 100644
index 000000000..1761547dd
--- /dev/null
+++ b/tools/bootconfig/samples/good-mixed-kv1.bconf
@@ -0,0 +1,3 @@
+# value -> subkey pattern
+key = value
+key.subkey = another-value
diff --git a/tools/bootconfig/samples/good-mixed-kv2.bconf b/tools/bootconfig/samples/good-mixed-kv2.bconf
new file mode 100644
index 000000000..6b32e0c38
--- /dev/null
+++ b/tools/bootconfig/samples/good-mixed-kv2.bconf
@@ -0,0 +1,3 @@
+# subkey -> value pattern
+key.subkey = value
+key = another-value
diff --git a/tools/bootconfig/samples/good-mixed-kv3.bconf b/tools/bootconfig/samples/good-mixed-kv3.bconf
new file mode 100644
index 000000000..2ce2b0222
--- /dev/null
+++ b/tools/bootconfig/samples/good-mixed-kv3.bconf
@@ -0,0 +1,6 @@
+# mixed key and subkeys with braces
+key = value
+key {
+	subkey1
+	subkey2 = foo
+}
diff --git a/tools/bootconfig/samples/good-mixed-override.bconf b/tools/bootconfig/samples/good-mixed-override.bconf
new file mode 100644
index 000000000..18195b287
--- /dev/null
+++ b/tools/bootconfig/samples/good-mixed-override.bconf
@@ -0,0 +1,4 @@
+key.foo = bar
+key = value
+# mixed key value can be overridden
+key := value2
diff --git a/tools/bootconfig/samples/good-nested-brace.bconf b/tools/bootconfig/samples/good-nested-brace.bconf
new file mode 100644
index 000000000..980d094f2
--- /dev/null
+++ b/tools/bootconfig/samples/good-nested-brace.bconf
@@ -0,0 +1,18 @@
+key1 {
+key2 {
+key3 {
+key4 {
+key5 {
+key6 {
+key7 {
+key8 {
+key9 {
+key10 {
+key11 {
+key12 {
+key13 {
+key14 {
+key15 {
+key16 {
+}}}}}}}}}}}}}}}}
+
diff --git a/tools/bootconfig/samples/good-override.bconf b/tools/bootconfig/samples/good-override.bconf
new file mode 100644
index 000000000..7d31d5f8f
--- /dev/null
+++ b/tools/bootconfig/samples/good-override.bconf
@@ -0,0 +1,6 @@
+# Override the value
+key.word = 1,2,4
+key.word := 2,3
+
+# No pre-defined key
+key.new.word := "new"
diff --git a/tools/bootconfig/samples/good-printables.bconf b/tools/bootconfig/samples/good-printables.bconf
new file mode 100644
index 000000000..ebb985a66
--- /dev/null
+++ b/tools/bootconfig/samples/good-printables.bconf
@@ -0,0 +1,2 @@
+key = "	
+ !#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~"
diff --git a/tools/bootconfig/samples/good-simple.bconf b/tools/bootconfig/samples/good-simple.bconf
new file mode 100644
index 000000000..37dd6d21c
--- /dev/null
+++ b/tools/bootconfig/samples/good-simple.bconf
@@ -0,0 +1,11 @@
+# A good simple bootconfig
+
+key.word1 = 1
+key.word2=2
+key.word3 = 3;
+
+key {
+word4 = 4 }
+
+key { word5 = 5; word6 = 6 }
+
diff --git a/tools/bootconfig/samples/good-single.bconf b/tools/bootconfig/samples/good-single.bconf
new file mode 100644
index 000000000..98e55ad8b
--- /dev/null
+++ b/tools/bootconfig/samples/good-single.bconf
@@ -0,0 +1,4 @@
+# single key style
+key = 1
+key2 = 2
+key3 = "alpha", "beta"
diff --git a/tools/bootconfig/samples/good-space-after-value.bconf b/tools/bootconfig/samples/good-space-after-value.bconf
new file mode 100644
index 000000000..56c15cbc5
--- /dev/null
+++ b/tools/bootconfig/samples/good-space-after-value.bconf
@@ -0,0 +1 @@
+key = "value"   
diff --git a/tools/bootconfig/samples/good-tree.bconf b/tools/bootconfig/samples/good-tree.bconf
new file mode 100644
index 000000000..f2ddefc8b
--- /dev/null
+++ b/tools/bootconfig/samples/good-tree.bconf
@@ -0,0 +1,12 @@
+key {
+  word {
+    tree {
+      value = "0"}
+  }
+  word2 {
+    tree {
+      value = 1,2 }
+  }
+}
+other.tree {
+  value = 2; value2 = 3;}