sched/cache: Keep nr_pref_llc_running in the runnable domain, to fix LLC mis-scheduling buggrafted

alb_break_llc() decides whether to break LLC preference during active
load balance. It does so by testing that every runnable fair task on the
source rq prefers its LLC:

	env->src_rq->nr_pref_llc_running == env->src_rq->cfs.h_nr_runnable

But the two counters cover different sets. nr_pref_llc_running is updated
in account_llc_enqueue()/account_llc_dequeue(), next to cfs_rq->nr_queued,
so it follows queued tasks. h_nr_runnable is updated in set_delayed()/
clear_delayed() and drops delay-dequeued tasks.

So under DELAY_DEQUEUE, a preferring task that goes to sleep stays counted
in nr_pref_llc_running while h_nr_runnable falls. The equality then breaks,
alb_break_llc() returns false, and active balance is free to pull a task
off its preferred LLC. Active balance only moves runnable tasks, and this
is the only LLC check it consults: once the stopper runs, LBF_ACTIVE_LB
skips the per-task test in can_migrate_task(). The runnable set is the one
we want.

Fix it on the counter side. A task should be counted in
nr_pref_llc_running exactly while it is both queued on its preferred LLC
(pref_llc_queued) and runnable (!sched_delayed). Define that membership
once in task_pref_llc_runnable(), and adjust the counter only through
pref_llc_running_inc()/pref_llc_running_dec() from the four sites that
change either input: account_llc_enqueue(), account_llc_dequeue(),
set_delayed() and clear_delayed(). Gating every update on the same
predicate keeps the delay, wake and dequeue paths from double-counting
or underflowing; see the comments at those sites for the ordering.

nr_llc_running and sd->llc_counts are not touched and stay on queued
semantics.

Fixes: 714059f79ff0 ("sched/cache: Handle moving single tasks to/from their preferred LLC")
Closes: https://lore.kernel.org/lkml/20260827135000.735138-1-zhanxusheng@xiaomi.com/
Reported-by: Zhan Xusheng <zhanxusheng@xiaomi.com>
Suggested-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Kayra Cizmeci <kayracizmeci@gmail.com>
Cc: <stable@kernel.org> # v7.2.x
Link: https://patch.msgid.link/06af61afedac32e6477f57feb4d658f6c411c3af.1790035273.git.tim.c.chen@linux.intel.com

3 files changed, 252 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/board/fsl,bcsr.yaml b/Documentation/devicetree/bindings/board/fsl,bcsr.yaml
new file mode 100644
index 000000000..df3dd8399
--- /dev/null
+++ b/Documentation/devicetree/bindings/board/fsl,bcsr.yaml
@@ -0,0 +1,32 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/board/fsl,bcsr.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Board Control and Status
+
+maintainers:
+  - Frank Li <Frank.Li@nxp.com>
+
+properties:
+  compatible:
+    enum:
+      - fsl,mpc8360mds-bcsr
+
+  reg:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    board@f8000000 {
+        compatible = "fsl,mpc8360mds-bcsr";
+        reg = <0xf8000000 0x8000>;
+    };
+
diff --git a/Documentation/devicetree/bindings/board/fsl,fpga-qixis-i2c.yaml b/Documentation/devicetree/bindings/board/fsl,fpga-qixis-i2c.yaml
new file mode 100644
index 000000000..e889dac05
--- /dev/null
+++ b/Documentation/devicetree/bindings/board/fsl,fpga-qixis-i2c.yaml
@@ -0,0 +1,128 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/board/fsl,fpga-qixis-i2c.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Freescale on-board FPGA connected on I2C bus
+
+maintainers:
+  - Frank Li <Frank.Li@nxp.com>
+
+properties:
+  compatible:
+    oneOf:
+      - items:
+          - enum:
+              - fsl,bsc9132qds-fpga
+          - const: fsl,fpga-qixis-i2c
+      - items:
+          - enum:
+              - fsl,ls1028aqds-fpga
+              - fsl,lx2160aqds-fpga
+          - const: fsl,fpga-qixis-i2c
+          - const: simple-mfd
+      - const: fsl,lx2160ardb-fpga
+
+  "#address-cells":
+    const: 1
+
+  "#size-cells":
+    const: 0
+
+  interrupts:
+    maxItems: 1
+
+  reg:
+    maxItems: 1
+
+  mux-controller:
+    $ref: /schemas/mux/reg-mux.yaml
+
+patternProperties:
+  "^gpio@[0-9a-f]+$":
+    type: object
+    additionalProperties: true
+
+    properties:
+      compatible:
+        contains:
+          enum:
+            - fsl,lx2160ardb-fpga-gpio-sfp
+
+required:
+  - compatible
+  - reg
+
+allOf:
+  - if:
+      properties:
+        compatible:
+          contains:
+            enum:
+              - fsl,lx2160ardb-fpga
+    then:
+      required:
+        - "#address-cells"
+        - "#size-cells"
+    else:
+      properties:
+        "#address-cells": false
+        "#size-cells": false
+
+additionalProperties: false
+
+examples:
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        board-control@66 {
+            compatible = "fsl,bsc9132qds-fpga", "fsl,fpga-qixis-i2c";
+            reg = <0x66>;
+        };
+    };
+
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        board-control@66 {
+            compatible = "fsl,ls1028aqds-fpga", "fsl,fpga-qixis-i2c",
+                         "simple-mfd";
+            reg = <0x66>;
+
+            mux-controller {
+                compatible = "reg-mux";
+                #mux-control-cells = <1>;
+                mux-reg-masks = <0x54 0xf0>; /* 0: reg 0x54, bits 7:4 */
+            };
+        };
+    };
+
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        board-control@66 {
+            compatible = "fsl,lx2160ardb-fpga";
+            reg = <0x66>;
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            gpio@19 {
+                compatible = "fsl,lx2160ardb-fpga-gpio-sfp";
+                reg = <0x19>;
+                gpio-controller;
+                #gpio-cells = <2>;
+                gpio-line-names =
+                    "SFP2_TX_EN", "",
+                    "", "",
+                    "SFP2_RX_LOS", "SFP2_TX_FAULT",
+                    "", "SFP2_MOD_ABS";
+            };
+        };
+    };
diff --git a/Documentation/devicetree/bindings/board/fsl,fpga-qixis.yaml b/Documentation/devicetree/bindings/board/fsl,fpga-qixis.yaml
new file mode 100644
index 000000000..ea1e3fbca
--- /dev/null
+++ b/Documentation/devicetree/bindings/board/fsl,fpga-qixis.yaml
@@ -0,0 +1,92 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/board/fsl,fpga-qixis.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Freescale on-board FPGA/CPLD
+
+maintainers:
+  - Frank Li <Frank.Li@nxp.com>
+
+properties:
+  compatible:
+    oneOf:
+      - items:
+          - const: fsl,p1022ds-fpga
+          - const: fsl,fpga-ngpixis
+      - items:
+          - enum:
+              - fsl,ls1088aqds-fpga
+              - fsl,ls1088ardb-fpga
+              - fsl,ls2080aqds-fpga
+              - fsl,ls2080ardb-fpga
+          - const: fsl,fpga-qixis
+      - items:
+          - enum:
+              - fsl,ls1021aqds-fpga
+              - fsl,ls1043aqds-fpga
+              - fsl,ls1043ardb-fpga
+              - fsl,ls1046aqds-fpga
+              - fsl,ls1046ardb-fpga
+              - fsl,ls208xaqds-fpga
+          - const: fsl,fpga-qixis
+          - const: simple-mfd
+      - enum:
+          - fsl,ls1043ardb-cpld
+          - fsl,ls1046ardb-cpld
+          - fsl,t1040rdb-cpld
+          - fsl,t1042rdb-cpld
+          - fsl,t1042rdb_pi-cpld
+
+  interrupts:
+    maxItems: 1
+
+  reg:
+    maxItems: 1
+
+  "#address-cells":
+    const: 1
+
+  "#size-cells":
+    const: 1
+
+  ranges:
+    maxItems: 1
+
+patternProperties:
+  '^mdio-mux@[a-f0-9,]+$':
+    $ref: /schemas/net/mdio-mux-mmioreg.yaml
+
+  '^gpio@[0-9a-f]+$':
+    type: object
+    additionalProperties: true
+
+    properties:
+      compatible:
+        contains:
+          enum:
+            - fsl,ls1046aqds-fpga-gpio-stat-pres2
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+    board-control@3 {
+        compatible = "fsl,p1022ds-fpga", "fsl,fpga-ngpixis";
+        reg = <3 0x30>;
+        interrupt-parent = <&mpic>;
+        interrupts = <8 IRQ_TYPE_LEVEL_LOW 0 0>;
+    };
+
+  - |
+    board-control@3 {
+        compatible = "fsl,ls2080ardb-fpga", "fsl,fpga-qixis";
+        reg = <0x3 0x10000>;
+    };
+