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

1 files changed, 220 insertions, 0 deletions

diff --git a/include/acpi/acbuffer.h b/include/acpi/acbuffer.h
new file mode 100644
index 000000000..7823df1c3
--- /dev/null
+++ b/include/acpi/acbuffer.h
@@ -0,0 +1,220 @@
+/* SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0 */
+/******************************************************************************
+ *
+ * Name: acbuffer.h - Support for buffers returned by ACPI predefined names
+ *
+ * Copyright (C) 2000 - 2026, Intel Corp.
+ *
+ *****************************************************************************/
+
+#ifndef __ACBUFFER_H__
+#define __ACBUFFER_H__
+
+/*
+ * Contains buffer structures for these predefined names:
+ * _FDE, _GRT, _GTM, _PLD, _SRT
+ */
+
+/*
+ * Note: C bitfields are not used for this reason:
+ *
+ * "Bitfields are great and easy to read, but unfortunately the C language
+ * does not specify the layout of bitfields in memory, which means they are
+ * essentially useless for dealing with packed data in on-disk formats or
+ * binary wire protocols." (Or ACPI tables and buffers.) "If you ask me,
+ * this decision was a design error in C. Ritchie could have picked an order
+ * and stuck with it." Norman Ramsey.
+ * See http://stackoverflow.com/a/1053662/41661
+ */
+
+/* _FDE return value */
+
+struct acpi_fde_info {
+	u32 floppy0;
+	u32 floppy1;
+	u32 floppy2;
+	u32 floppy3;
+	u32 tape;
+};
+
+/*
+ * _GRT return value
+ * _SRT input value
+ */
+struct acpi_grt_info {
+	u16 year;
+	u8 month;
+	u8 day;
+	u8 hour;
+	u8 minute;
+	u8 second;
+	u8 valid;
+	u16 milliseconds;
+	u16 timezone;
+	u8 daylight;
+	u8 reserved[3];
+};
+
+/* _GTM return value */
+
+struct acpi_gtm_info {
+	u32 pio_speed0;
+	u32 dma_speed0;
+	u32 pio_speed1;
+	u32 dma_speed1;
+	u32 flags;
+};
+
+/*
+ * Formatted _PLD return value. The minimum size is a package containing
+ * one buffer.
+ * Revision 1: Buffer is 16 bytes (128 bits)
+ * Revision 2: Buffer is 20 bytes (160 bits)
+ *
+ * Note: This structure is returned from the acpi_decode_pld_buffer
+ * interface.
+ */
+struct acpi_pld_info {
+	u8 revision;
+	u8 ignore_color;
+	u8 red;
+	u8 green;
+	u8 blue;
+	u16 width;
+	u16 height;
+	u8 user_visible;
+	u8 dock;
+	u8 lid;
+	u8 panel;
+	u8 vertical_position;
+	u8 horizontal_position;
+	u8 shape;
+	u8 group_orientation;
+	u8 group_token;
+	u8 group_position;
+	u8 bay;
+	u8 ejectable;
+	u8 ospm_eject_required;
+	u8 cabinet_number;
+	u8 card_cage_number;
+	u8 reference;
+	u8 rotation;
+	u8 order;
+	u8 reserved;
+	u16 vertical_offset;
+	u16 horizontal_offset;
+};
+
+/*
+ * Macros to:
+ *     1) Convert a _PLD buffer to internal struct acpi_pld_info format - ACPI_PLD_GET*
+ *        (Used by acpi_decode_pld_buffer)
+ *     2) Construct a _PLD buffer - ACPI_PLD_SET*
+ *        (Intended for BIOS use only)
+ */
+#define ACPI_PLD_REV1_BUFFER_SIZE               16	/* For Revision 1 of the buffer (From ACPI spec) */
+#define ACPI_PLD_REV2_BUFFER_SIZE               20	/* For Revision 2 of the buffer (From ACPI spec) */
+#define ACPI_PLD_BUFFER_SIZE                    20	/* For Revision 2 of the buffer (From ACPI spec) */
+
+/* First 32-bit dword, bits 0:32 */
+
+#define ACPI_PLD_GET_REVISION(dword)            ACPI_GET_BITS (dword, 0, ACPI_7BIT_MASK)
+#define ACPI_PLD_SET_REVISION(dword,value)      ACPI_SET_BITS (dword, 0, ACPI_7BIT_MASK, value)	/* Offset 0, Len 7 */
+
+#define ACPI_PLD_GET_IGNORE_COLOR(dword)        ACPI_GET_BITS (dword, 7, ACPI_1BIT_MASK)
+#define ACPI_PLD_SET_IGNORE_COLOR(dword,value)  ACPI_SET_BITS (dword, 7, ACPI_1BIT_MASK, value)	/* Offset 7, Len 1 */
+
+#define ACPI_PLD_GET_RED(dword)                 ACPI_GET_BITS (dword, 8, ACPI_8BIT_MASK)
+#define ACPI_PLD_SET_RED(dword,value)           ACPI_SET_BITS (dword, 8, ACPI_8BIT_MASK, value)	/* Offset 8, Len 8 */
+
+#define ACPI_PLD_GET_GREEN(dword)               ACPI_GET_BITS (dword, 16, ACPI_8BIT_MASK)
+#define ACPI_PLD_SET_GREEN(dword,value)         ACPI_SET_BITS (dword, 16, ACPI_8BIT_MASK, value)	/* Offset 16, Len 8 */
+
+#define ACPI_PLD_GET_BLUE(dword)                ACPI_GET_BITS (dword, 24, ACPI_8BIT_MASK)
+#define ACPI_PLD_SET_BLUE(dword,value)          ACPI_SET_BITS (dword, 24, ACPI_8BIT_MASK, value)	/* Offset 24, Len 8 */
+
+/* Second 32-bit dword, bits 33:63 */
+
+#define ACPI_PLD_GET_WIDTH(dword)               ACPI_GET_BITS (dword, 0, ACPI_16BIT_MASK)
+#define ACPI_PLD_SET_WIDTH(dword,value)         ACPI_SET_BITS (dword, 0, ACPI_16BIT_MASK, value)	/* Offset 32+0=32, Len 16 */
+
+#define ACPI_PLD_GET_HEIGHT(dword)              ACPI_GET_BITS (dword, 16, ACPI_16BIT_MASK)
+#define ACPI_PLD_SET_HEIGHT(dword,value)        ACPI_SET_BITS (dword, 16, ACPI_16BIT_MASK, value)	/* Offset 32+16=48, Len 16 */
+
+/* Third 32-bit dword, bits 64:95 */
+
+#define ACPI_PLD_GET_USER_VISIBLE(dword)        ACPI_GET_BITS (dword, 0, ACPI_1BIT_MASK)
+#define ACPI_PLD_SET_USER_VISIBLE(dword,value)  ACPI_SET_BITS (dword, 0, ACPI_1BIT_MASK, value)	/* Offset 64+0=64, Len 1 */
+
+#define ACPI_PLD_GET_DOCK(dword)                ACPI_GET_BITS (dword, 1, ACPI_1BIT_MASK)
+#define ACPI_PLD_SET_DOCK(dword,value)          ACPI_SET_BITS (dword, 1, ACPI_1BIT_MASK, value)	/* Offset 64+1=65, Len 1 */
+
+#define ACPI_PLD_GET_LID(dword)                 ACPI_GET_BITS (dword, 2, ACPI_1BIT_MASK)
+#define ACPI_PLD_SET_LID(dword,value)           ACPI_SET_BITS (dword, 2, ACPI_1BIT_MASK, value)	/* Offset 64+2=66, Len 1 */
+
+#define ACPI_PLD_GET_PANEL(dword)               ACPI_GET_BITS (dword, 3, ACPI_3BIT_MASK)
+#define ACPI_PLD_SET_PANEL(dword,value)         ACPI_SET_BITS (dword, 3, ACPI_3BIT_MASK, value)	/* Offset 64+3=67, Len 3 */
+
+#define ACPI_PLD_GET_VERTICAL(dword)            ACPI_GET_BITS (dword, 6, ACPI_2BIT_MASK)
+#define ACPI_PLD_SET_VERTICAL(dword,value)      ACPI_SET_BITS (dword, 6, ACPI_2BIT_MASK, value)	/* Offset 64+6=70, Len 2 */
+
+#define ACPI_PLD_GET_HORIZONTAL(dword)          ACPI_GET_BITS (dword, 8, ACPI_2BIT_MASK)
+#define ACPI_PLD_SET_HORIZONTAL(dword,value)    ACPI_SET_BITS (dword, 8, ACPI_2BIT_MASK, value)	/* Offset 64+8=72, Len 2 */
+
+#define ACPI_PLD_GET_SHAPE(dword)               ACPI_GET_BITS (dword, 10, ACPI_4BIT_MASK)
+#define ACPI_PLD_SET_SHAPE(dword,value)         ACPI_SET_BITS (dword, 10, ACPI_4BIT_MASK, value)	/* Offset 64+10=74, Len 4 */
+
+#define ACPI_PLD_GET_ORIENTATION(dword)         ACPI_GET_BITS (dword, 14, ACPI_1BIT_MASK)
+#define ACPI_PLD_SET_ORIENTATION(dword,value)   ACPI_SET_BITS (dword, 14, ACPI_1BIT_MASK, value)	/* Offset 64+14=78, Len 1 */
+
+#define ACPI_PLD_GET_TOKEN(dword)               ACPI_GET_BITS (dword, 15, ACPI_8BIT_MASK)
+#define ACPI_PLD_SET_TOKEN(dword,value)         ACPI_SET_BITS (dword, 15, ACPI_8BIT_MASK, value)	/* Offset 64+15=79, Len 8 */
+
+#define ACPI_PLD_GET_POSITION(dword)            ACPI_GET_BITS (dword, 23, ACPI_8BIT_MASK)
+#define ACPI_PLD_SET_POSITION(dword,value)      ACPI_SET_BITS (dword, 23, ACPI_8BIT_MASK, value)	/* Offset 64+23=87, Len 8 */
+
+#define ACPI_PLD_GET_BAY(dword)                 ACPI_GET_BITS (dword, 31, ACPI_1BIT_MASK)
+#define ACPI_PLD_SET_BAY(dword,value)           ACPI_SET_BITS (dword, 31, ACPI_1BIT_MASK, value)	/* Offset 64+31=95, Len 1 */
+
+/* Fourth 32-bit dword, bits 96:127 */
+
+#define ACPI_PLD_GET_EJECTABLE(dword)           ACPI_GET_BITS (dword, 0, ACPI_1BIT_MASK)
+#define ACPI_PLD_SET_EJECTABLE(dword,value)     ACPI_SET_BITS (dword, 0, ACPI_1BIT_MASK, value)	/* Offset 96+0=96, Len 1 */
+
+#define ACPI_PLD_GET_OSPM_EJECT(dword)          ACPI_GET_BITS (dword, 1, ACPI_1BIT_MASK)
+#define ACPI_PLD_SET_OSPM_EJECT(dword,value)    ACPI_SET_BITS (dword, 1, ACPI_1BIT_MASK, value)	/* Offset 96+1=97, Len 1 */
+
+#define ACPI_PLD_GET_CABINET(dword)             ACPI_GET_BITS (dword, 2, ACPI_8BIT_MASK)
+#define ACPI_PLD_SET_CABINET(dword,value)       ACPI_SET_BITS (dword, 2, ACPI_8BIT_MASK, value)	/* Offset 96+2=98, Len 8 */
+
+#define ACPI_PLD_GET_CARD_CAGE(dword)           ACPI_GET_BITS (dword, 10, ACPI_8BIT_MASK)
+#define ACPI_PLD_SET_CARD_CAGE(dword,value)     ACPI_SET_BITS (dword, 10, ACPI_8BIT_MASK, value)	/* Offset 96+10=106, Len 8 */
+
+#define ACPI_PLD_GET_REFERENCE(dword)           ACPI_GET_BITS (dword, 18, ACPI_1BIT_MASK)
+#define ACPI_PLD_SET_REFERENCE(dword,value)     ACPI_SET_BITS (dword, 18, ACPI_1BIT_MASK, value)	/* Offset 96+18=114, Len 1 */
+
+#define ACPI_PLD_GET_ROTATION(dword)            ACPI_GET_BITS (dword, 19, ACPI_4BIT_MASK)
+#define ACPI_PLD_SET_ROTATION(dword,value)      ACPI_SET_BITS (dword, 19, ACPI_4BIT_MASK, value)	/* Offset 96+19=115, Len 4 */
+
+#define ACPI_PLD_GET_ORDER(dword)               ACPI_GET_BITS (dword, 23, ACPI_5BIT_MASK)
+#define ACPI_PLD_SET_ORDER(dword,value)         ACPI_SET_BITS (dword, 23, ACPI_5BIT_MASK, value)	/* Offset 96+23=119, Len 5 */
+
+/* Fifth 32-bit dword, bits 128:159 (Revision 2 of _PLD only) */
+
+#define ACPI_PLD_GET_VERT_OFFSET(dword)         ACPI_GET_BITS (dword, 0, ACPI_16BIT_MASK)
+#define ACPI_PLD_SET_VERT_OFFSET(dword,value)   ACPI_SET_BITS (dword, 0, ACPI_16BIT_MASK, value)	/* Offset 128+0=128, Len 16 */
+
+#define ACPI_PLD_GET_HORIZ_OFFSET(dword)        ACPI_GET_BITS (dword, 16, ACPI_16BIT_MASK)
+#define ACPI_PLD_SET_HORIZ_OFFSET(dword,value)  ACPI_SET_BITS (dword, 16, ACPI_16BIT_MASK, value)	/* Offset 128+16=144, Len 16 */
+
+/* Panel position defined in _PLD section of ACPI Specification 6.3 */
+
+#define ACPI_PLD_PANEL_TOP      0
+#define ACPI_PLD_PANEL_BOTTOM   1
+#define ACPI_PLD_PANEL_LEFT     2
+#define ACPI_PLD_PANEL_RIGHT    3
+#define ACPI_PLD_PANEL_FRONT    4
+#define ACPI_PLD_PANEL_BACK     5
+#define ACPI_PLD_PANEL_UNKNOWN  6
+
+#endif				/* ACBUFFER_H */