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, 167 insertions, 0 deletions

diff --git a/drivers/input/mouse/trackpoint.h b/drivers/input/mouse/trackpoint.h
new file mode 100644
index 000000000..3e03cdb39
--- /dev/null
+++ b/drivers/input/mouse/trackpoint.h
@@ -0,0 +1,167 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * IBM TrackPoint PS/2 mouse driver
+ *
+ * Stephen Evanchik <evanchsa@gmail.com>
+ */
+
+#ifndef _TRACKPOINT_H
+#define _TRACKPOINT_H
+
+/*
+ * These constants are from the TrackPoint System
+ * Engineering documentation Version 4 from IBM Watson
+ * research:
+ *	http://wwwcssrv.almaden.ibm.com/trackpoint/download.html
+ */
+
+#define TP_COMMAND		0xE2	/* Commands start with this */
+
+#define TP_READ_ID		0xE1	/* Sent for device identification */
+
+/*
+ * Valid first byte responses to the "Read Secondary ID" (0xE1) command.
+ * 0x01 was the original IBM trackpoint, others implement very limited
+ * subset of trackpoint features.
+ */
+#define TP_VARIANT_IBM			0x01
+#define TP_VARIANT_ALPS			0x02
+#define TP_VARIANT_ELAN			0x03
+#define TP_VARIANT_NXP			0x04
+#define TP_VARIANT_JYT_SYNAPTICS	0x05
+#define TP_VARIANT_SYNAPTICS		0x06
+
+/*
+ * Commands
+ */
+#define TP_RECALIB		0x51	/* Recalibrate */
+#define TP_POWER_DOWN		0x44	/* Can only be undone through HW reset */
+#define TP_EXT_DEV		0x21	/* Determines if external device is connected (RO) */
+#define TP_EXT_BTN		0x4B	/* Read extended button status */
+#define TP_POR			0x7F	/* Execute Power on Reset */
+#define TP_POR_RESULTS		0x25	/* Read Power on Self test results */
+#define TP_DISABLE_EXT		0x40	/* Disable external pointing device */
+#define TP_ENABLE_EXT		0x41	/* Enable external pointing device */
+
+/*
+ * Mode manipulation
+ */
+#define TP_SET_SOFT_TRANS	0x4E	/* Set mode */
+#define TP_CANCEL_SOFT_TRANS	0xB9	/* Cancel mode */
+#define TP_SET_HARD_TRANS	0x45	/* Mode can only be set */
+
+
+/*
+ * Register oriented commands/properties
+ */
+#define TP_WRITE_MEM		0x81
+#define TP_READ_MEM		0x80	/* Not used in this implementation */
+
+/*
+* RAM Locations for properties
+ */
+#define TP_SENS			0x4A	/* Sensitivity */
+#define TP_MB			0x4C	/* Read Middle Button Status (RO) */
+#define TP_INERTIA		0x4D	/* Negative Inertia */
+#define TP_SPEED		0x60	/* Speed of TP Cursor */
+#define TP_REACH		0x57	/* Backup for Z-axis press */
+#define TP_DRAGHYS		0x58	/* Drag Hysteresis */
+					/* (how hard it is to drag */
+					/* with Z-axis pressed) */
+
+#define TP_DOUBLETAP		0x58	/* TrackPoint doubletap register */
+
+#define TP_MINDRAG		0x59	/* Minimum amount of force needed */
+					/* to trigger dragging */
+
+#define TP_THRESH		0x5C	/* Minimum value for a Z-axis press */
+#define TP_UP_THRESH		0x5A	/* Used to generate a 'click' on Z-axis */
+#define TP_Z_TIME		0x5E	/* How sharp of a press */
+#define TP_JENKS_CURV		0x5D	/* Minimum curvature for double click */
+#define TP_DRIFT_TIME		0x5F	/* How long a 'hands off' condition */
+					/* must last (x*107ms) for drift */
+					/* correction to occur */
+
+/*
+ * Toggling Flag bits
+ */
+#define TP_TOGGLE		0x47	/* Toggle command */
+
+#define TP_TOGGLE_MB		0x23	/* Disable/Enable Middle Button */
+#define TP_MASK_MB			0x01
+#define TP_TOGGLE_EXT_DEV	0x23	/* Disable external device */
+#define TP_MASK_EXT_DEV			0x02
+#define TP_TOGGLE_DRIFT		0x23	/* Drift Correction */
+#define TP_MASK_DRIFT			0x80
+#define TP_TOGGLE_BURST		0x28	/* Burst Mode */
+#define TP_MASK_BURST			0x80
+#define TP_TOGGLE_PTSON		0x2C	/* Press to Select */
+#define TP_MASK_PTSON			0x01
+#define TP_TOGGLE_HARD_TRANS	0x2C	/* Alternate method to set Hard Transparency */
+#define TP_MASK_HARD_TRANS		0x80
+#define TP_TOGGLE_TWOHAND	0x2D	/* Two handed */
+#define TP_MASK_TWOHAND			0x01
+#define TP_TOGGLE_STICKY_TWO	0x2D	/* Sticky two handed */
+#define TP_MASK_STICKY_TWO		0x04
+#define TP_TOGGLE_SKIPBACK	0x2D	/* Suppress movement after drag release */
+#define TP_MASK_SKIPBACK		0x08
+#define TP_TOGGLE_SOURCE_TAG	0x20	/* Bit 3 of the first packet will be set to
+					   to the origin of the packet (external or TP) */
+#define TP_MASK_SOURCE_TAG		0x80
+#define TP_TOGGLE_EXT_TAG	0x22	/* Bit 3 of the first packet coming from the
+					   external device will be forced to 1 */
+#define TP_MASK_EXT_TAG			0x04
+
+/* Doubletap register values */
+#define TP_DOUBLETAP_ENABLE	0xFF	/* Enable value */
+#define TP_DOUBLETAP_DISABLE	0xFE	/* Disable value */
+
+/* Power on Self Test Results */
+#define TP_POR_SUCCESS		0x3B
+
+/*
+ * Default power on values
+ */
+#define TP_DEF_SENS		0x80
+#define TP_DEF_INERTIA		0x06
+#define TP_DEF_SPEED		0x61
+#define TP_DEF_REACH		0x0A
+
+#define TP_DEF_DRAGHYS		0xFF
+#define TP_DEF_MINDRAG		0x14
+
+#define TP_DEF_THRESH		0x08
+#define TP_DEF_UP_THRESH	0xFF
+#define TP_DEF_Z_TIME		0x26
+#define TP_DEF_JENKS_CURV	0x87
+#define TP_DEF_DRIFT_TIME	0x05
+
+/* Toggles */
+#define TP_DEF_MB		0x00
+#define TP_DEF_PTSON		0x00
+#define TP_DEF_SKIPBACK		0x00
+#define TP_DEF_EXT_DEV		0x00	/* 0 means enabled */
+#define TP_DEF_TWOHAND		0x00
+#define TP_DEF_SOURCE_TAG	0x00
+
+#define MAKE_PS2_CMD(params, results, cmd) ((params<<12) | (results<<8) | (cmd))
+
+struct trackpoint_data {
+	u8 variant_id;
+	u8 firmware_id;
+
+	u8 sensitivity, speed, inertia, reach;
+	u8 draghys, mindrag;
+	u8 thresh, upthresh;
+	u8 ztime, jenks;
+	u8 drift_time;
+
+	/* toggles */
+	bool press_to_select;
+	bool skipback;
+	bool ext_dev;
+};
+
+int trackpoint_detect(struct psmouse *psmouse, bool set_properties);
+
+#endif /* _TRACKPOINT_H */