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>

4 files changed, 517 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/eeprom/at24.yaml b/Documentation/devicetree/bindings/eeprom/at24.yaml
new file mode 100644
index 000000000..ef88f4692
--- /dev/null
+++ b/Documentation/devicetree/bindings/eeprom/at24.yaml
@@ -0,0 +1,236 @@
+# SPDX-License-Identifier: GPL-2.0-only
+# Copyright 2019 BayLibre SAS
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/eeprom/at24.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: I2C EEPROMs compatible with Atmel's AT24
+
+maintainers:
+  - Bartosz Golaszewski <bgolaszewski@baylibre.com>
+
+allOf:
+  - $ref: /schemas/nvmem/nvmem.yaml
+  - $ref: /schemas/nvmem/nvmem-deprecated-cells.yaml
+
+select:
+  properties:
+    compatible:
+      contains:
+        anyOf:
+          - pattern: "^atmel,(24(c|cs|mac)[0-9]+|spd)$"
+          - enum: ["microchip,24aa025e48", "microchip,24aa025e64"]
+  required:
+    - compatible
+
+properties:
+  $nodename:
+    pattern: "^eeprom@[0-9a-f]{1,2}$"
+
+  # There are multiple known vendors who manufacture EEPROM chips compatible
+  # with Atmel's AT24. The compatible string requires either a single item
+  # if the memory comes from Atmel (in which case the vendor part must be
+  # 'atmel') or two items with the same 'model' part where the vendor part of
+  # the first one is the actual manufacturer and the second item is the
+  # corresponding 'atmel,<model>' from Atmel.
+  compatible:
+    oneOf:
+      - allOf:
+          - minItems: 1
+            items:
+              - pattern: "^(atmel|catalyst|microchip|nxp|ramtron|renesas|rohm|st),(24(c|cs|lc|mac)[0-9]+|spd)$"
+              - pattern: "^atmel,(24(c|cs|mac)[0-9]+|spd)$"
+          - oneOf:
+              - items:
+                  pattern: c00$
+              - items:
+                  pattern: c01$
+              - items:
+                  pattern: cs01$
+              - items:
+                  pattern: c02$
+              - items:
+                  pattern: cs02$
+              - items:
+                  pattern: mac402$
+              - items:
+                  pattern: mac602$
+              - items:
+                  pattern: c04$
+              - items:
+                  pattern: cs04$
+              - items:
+                  pattern: c08$
+              - items:
+                  pattern: cs08$
+              - items:
+                  pattern: c16$
+              - items:
+                  pattern: cs16$
+              - items:
+                  pattern: c32$
+              - items:
+                  pattern: cs32$
+              - items:
+                  pattern: c64$
+              - items:
+                  pattern: cs64$
+              - items:
+                  pattern: c128$
+              - items:
+                  pattern: cs128$
+              - items:
+                  pattern: c256$
+              - items:
+                  pattern: cs256$
+              - items:
+                  pattern: c512$
+              - items:
+                  pattern: cs512$
+              - items:
+                  pattern: c1024$
+              - items:
+                  pattern: cs1024$
+              - items:
+                  pattern: c1025$
+              - items:
+                  pattern: cs1025$
+              - items:
+                  pattern: c2048$
+              - items:
+                  pattern: cs2048$
+              - items:
+                  pattern: spd$
+      # These are special cases that don't conform to the above pattern.
+      # Each requires a standard at24 model as fallback.
+      - items:
+          - enum:
+              - rohm,br24g01
+              - rohm,br24t01
+          - const: atmel,24c01
+      - items:
+          - enum:
+              - nxp,se97b
+              - renesas,r1ex24002
+          - const: atmel,24c02
+      - items:
+          - enum:
+              - belling,bl24c04a
+              - giantec,gt24c04a
+              - onnn,cat24c04
+              - onnn,cat24c05
+              - rohm,br24g04
+          - const: atmel,24c04
+      - items:
+          - enum:
+              - belling,bl24c16a
+              - belling,bl24c16f
+              - renesas,r1ex24016
+          - const: atmel,24c16
+      - items:
+          - const: giantec,gt24c32a
+          - const: atmel,24c32
+      - items:
+          - enum:
+              - belling,bl24s64
+              - giantec,gt24p64a
+              - onnn,n24s64b
+              - puya,p24c64f
+          - const: atmel,24c64
+      - items:
+          - enum:
+              - giantec,gt24p128e
+              - giantec,gt24p128f
+              - puya,p24c128f
+              - renesas,r1ex24128
+              - samsung,s524ad0xd1
+          - const: atmel,24c128
+      - items:
+          - enum:
+              - giantec,gt24c256c
+              - puya,p24c256c
+          - const: atmel,24c256
+      - items:
+          - const: microchip,24aa025e48
+      - items:
+          - const: microchip,24aa025e64
+      - items:
+          - const: st,24256e-wl
+      - pattern: '^atmel,24c(32|64)d-wl$' # Actual vendor is st
+
+  label:
+    description: Descriptive name of the EEPROM.
+
+  reg:
+    maxItems: 1
+
+  pagesize:
+    description:
+      The length of the pagesize for writing. Please consult the
+      manual of your device, that value varies a lot. A wrong value
+      may result in data loss! If not specified, a safety value of
+      '1' is used which will be very slow.
+    $ref: /schemas/types.yaml#/definitions/uint32
+    enum: [1, 8, 16, 32, 64, 128, 256]
+    default: 1
+
+  read-only:
+    $ref: /schemas/types.yaml#/definitions/flag
+    description:
+      Disables writes to the eeprom.
+
+  size:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description:
+      Total eeprom size in bytes.
+
+  no-read-rollover:
+    $ref: /schemas/types.yaml#/definitions/flag
+    description:
+      Indicates that the multi-address eeprom does not automatically roll
+      over reads to the next slave address. Please consult the manual of
+      your device.
+
+  wp-gpios: true
+
+  address-width:
+    description:
+      Number of address bits.
+    $ref: /schemas/types.yaml#/definitions/uint32
+    default: 8
+    enum: [ 8, 16 ]
+
+  num-addresses:
+    description:
+      Total number of i2c slave addresses this device takes.
+    $ref: /schemas/types.yaml#/definitions/uint32
+    default: 1
+    minimum: 1
+    maximum: 8
+
+  vcc-supply:
+    description:
+      phandle of the regulator that provides the supply voltage.
+
+required:
+  - compatible
+  - reg
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    i2c {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      eeprom@52 {
+          compatible = "microchip,24c32", "atmel,24c32";
+          reg = <0x52>;
+          pagesize = <32>;
+          wp-gpios = <&gpio1 3 0>;
+          num-addresses = <8>;
+      };
+    };
+...
diff --git a/Documentation/devicetree/bindings/eeprom/at25.yaml b/Documentation/devicetree/bindings/eeprom/at25.yaml
new file mode 100644
index 000000000..bb78e12b8
--- /dev/null
+++ b/Documentation/devicetree/bindings/eeprom/at25.yaml
@@ -0,0 +1,159 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/eeprom/at25.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: SPI EEPROMs or FRAMs compatible with Atmel's AT25
+
+maintainers:
+  - Christian Eggers <ceggers@arri.de>
+
+properties:
+  $nodename:
+    anyOf:
+      - pattern: "^eeprom@[0-9a-f]{1,2}$"
+      - pattern: "^fram@[0-9a-f]{1,2}$"
+
+  # There are multiple known vendors who manufacture EEPROM chips compatible
+  # with Atmel's AT25. The compatible string requires two items where the
+  # 'vendor' and 'model' parts of the first are the actual chip and the second
+  # item is fixed to "atmel,at25". Some existing bindings only have the
+  # "atmel,at25" part and should be fixed by somebody who knows vendor and
+  # product.
+  compatible:
+    oneOf:
+      - items:
+          - enum:
+              - anvo,anv32c81w
+              - anvo,anv32e61w
+              - atmel,at25256B
+              - fujitsu,mb85rs1mt
+              - fujitsu,mb85rs256
+              - fujitsu,mb85rs64
+              - microchip,25aa010a
+              - microchip,at25160bn
+              - microchip,25lc040
+              - st,m95m02
+              - st,m95256
+              - st,m95640
+              - cypress,fm25
+
+          - const: atmel,at25
+
+      # Please don't use this alternative for new bindings.
+      - items:
+          - const: atmel,at25
+
+  reg:
+    maxItems: 1
+
+  pagesize:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    enum: [1, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768, 65536, 131072]
+    description:
+      Size of the eeprom page. FRAMs don't have pages.
+
+  size:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description:
+      Total eeprom size in bytes.
+      Also used for FRAMs without device ID where the size cannot be detected.
+
+  address-width:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    enum: [ 8, 9, 16, 24 ]
+    description:
+      Number of address bits.
+      For 9 bits, the MSB of the address is sent as bit 3 of the instruction
+      byte, before the address byte.
+
+  spi-cpha: true
+
+  spi-cpol: true
+
+  read-only:
+    description:
+      Disable writes to the eeprom.
+    type: boolean
+
+  wp-gpios:
+    maxItems: 1
+    description:
+      GPIO to which the write-protect pin of the chip is connected.
+
+  # Deprecated: at25,byte-len, at25,addr-mode, at25,page-size
+  at25,byte-len:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description:
+      Total eeprom size in bytes. Deprecated, use "size" property instead.
+    deprecated: true
+
+  at25,addr-mode:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description:
+      Addr-mode flags, as defined in include/linux/spi/eeprom.h.
+      Deprecated, use "address-width" property instead.
+    deprecated: true
+
+  at25,page-size:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description:
+      Size of the eeprom page. Deprecated, use "pagesize" property instead.
+    deprecated: true
+
+required:
+  - compatible
+  - reg
+  - spi-max-frequency
+
+allOf:
+  - $ref: /schemas/spi/spi-peripheral-props.yaml#
+  - $ref: /schemas/nvmem/nvmem.yaml
+  - if:
+      properties:
+        compatible:
+          not:
+            contains:
+              const: cypress,fm25
+    then:
+      required:
+        - pagesize
+        - size
+        - address-width
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+    spi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        eeprom@0 {
+            compatible = "st,m95256", "atmel,at25";
+            reg = <0>;
+            spi-max-frequency = <5000000>;
+            spi-cpha;
+            spi-cpol;
+            wp-gpios = <&gpio1 3 0>;
+
+            pagesize = <64>;
+            size = <32768>;
+            address-width = <16>;
+        };
+
+        fram@1 {
+            compatible = "cypress,fm25", "atmel,at25";
+            reg = <1>;
+            spi-max-frequency = <40000000>;
+        };
+
+        fram@2 {
+            compatible = "cypress,fm25", "atmel,at25";
+            reg = <2>;
+            spi-max-frequency = <20000000>;
+            size = <2048>;
+        };
+    };
diff --git a/Documentation/devicetree/bindings/eeprom/microchip,93lc46b.yaml b/Documentation/devicetree/bindings/eeprom/microchip,93lc46b.yaml
new file mode 100644
index 000000000..144e86ce5
--- /dev/null
+++ b/Documentation/devicetree/bindings/eeprom/microchip,93lc46b.yaml
@@ -0,0 +1,70 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/eeprom/microchip,93lc46b.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Microchip 93xx46 SPI compatible EEPROM family
+
+maintainers:
+  - Cory Tusar <cory.tusar@pid1solutions.com>
+
+properties:
+  compatible:
+    enum:
+      - atmel,at93c46
+      - atmel,at93c46d
+      - atmel,at93c56
+      - atmel,at93c66
+      - eeprom-93xx46
+      - microchip,93lc46b
+
+  data-size:
+    description: number of data bits per word
+    $ref: /schemas/types.yaml#/definitions/uint32
+    enum: [8, 16]
+
+  reg:
+    description: chip select of EEPROM
+    maxItems: 1
+
+  read-only:
+    description:
+      parameter-less property which disables writes to the EEPROM
+    type: boolean
+
+  select-gpios:
+    description:
+      specifies the GPIO that needs to be asserted prior to each access
+      of EEPROM (e.g. for SPI bus multiplexing)
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - data-size
+  - spi-max-frequency
+
+allOf:
+  - $ref: /schemas/spi/spi-peripheral-props.yaml#
+  - $ref: /schemas/nvmem/nvmem.yaml
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+
+    spi {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      eeprom@0 {
+        compatible = "eeprom-93xx46";
+        reg = <0>;
+        spi-max-frequency = <1000000>;
+        spi-cs-high;
+        data-size = <8>;
+        select-gpios = <&gpio4 4 GPIO_ACTIVE_HIGH>;
+      };
+    };
diff --git a/Documentation/devicetree/bindings/eeprom/st,m24lr.yaml b/Documentation/devicetree/bindings/eeprom/st,m24lr.yaml
new file mode 100644
index 000000000..0a0820e9d
--- /dev/null
+++ b/Documentation/devicetree/bindings/eeprom/st,m24lr.yaml
@@ -0,0 +1,52 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/eeprom/st,m24lr.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: STMicroelectronics M24LR NFC/RFID EEPROM
+
+maintainers:
+  - Abd-Alrhman Masalkhi <abd.masalkhi@gmail.com>
+
+description:
+  STMicroelectronics M24LR series are dual-interface (RF + I2C)
+  EEPROM chips. These devices support I2C-based access to both
+  memory and a system area that controls authentication and configuration.
+  They expose two I2C addresses, one for the system parameter sector and
+  one for the EEPROM.
+
+allOf:
+  - $ref: /schemas/nvmem/nvmem.yaml#
+
+properties:
+  compatible:
+    enum:
+      - st,m24lr04e-r
+      - st,m24lr16e-r
+      - st,m24lr64e-r
+
+  reg:
+    items:
+      - description: I2C address used for control/system registers
+      - description: I2C address used for EEPROM memory access
+
+required:
+  - compatible
+  - reg
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    i2c {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      eeprom@57 {
+        compatible = "st,m24lr04e-r";
+        reg = <0x57>, /* primary-device */
+              <0x53>; /* secondary-device */
+      };
+    };
+...