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, 138 insertions, 0 deletions

diff --git a/drivers/video/fbdev/edid.h b/drivers/video/fbdev/edid.h
new file mode 100644
index 000000000..d03a232d9
--- /dev/null
+++ b/drivers/video/fbdev/edid.h
@@ -0,0 +1,138 @@
+/* 
+ * drivers/video/edid.h - EDID/DDC Header
+ *
+ * Based on:
+ *   1. XFree86 4.3.0, edid.h
+ *      Copyright 1998 by Egbert Eich <Egbert.Eich@Physik.TU-Darmstadt.DE>
+ * 
+ *   2. John Fremlin <vii@users.sourceforge.net> and 
+ *      Ani Joshi <ajoshi@unixbox.com>
+ *
+ * DDC is a Trademark of VESA (Video Electronics Standard Association).
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file COPYING in the main directory of this archive
+ * for more details.
+*/
+
+#ifndef __EDID_H__
+#define __EDID_H__
+
+#define EDID_LENGTH				0x80
+#define EDID_HEADER				0x00
+#define EDID_HEADER_END				0x07
+
+#define ID_MANUFACTURER_NAME			0x08
+#define ID_MANUFACTURER_NAME_END		0x09
+#define ID_MODEL				0x0a
+
+#define ID_SERIAL_NUMBER			0x0c
+
+#define MANUFACTURE_WEEK			0x10
+#define MANUFACTURE_YEAR			0x11
+
+#define EDID_STRUCT_VERSION			0x12
+#define EDID_STRUCT_REVISION			0x13
+
+#define EDID_STRUCT_DISPLAY                     0x14
+
+#define DPMS_FLAGS				0x18
+#define ESTABLISHED_TIMING_1			0x23
+#define ESTABLISHED_TIMING_2			0x24
+#define MANUFACTURERS_TIMINGS			0x25
+
+/* standard timings supported */
+#define STD_TIMING                              8
+#define STD_TIMING_DESCRIPTION_SIZE             2
+#define STD_TIMING_DESCRIPTIONS_START           0x26
+
+#define DETAILED_TIMING_DESCRIPTIONS_START	0x36
+#define DETAILED_TIMING_DESCRIPTION_SIZE	18
+#define NO_DETAILED_TIMING_DESCRIPTIONS		4
+
+#define DETAILED_TIMING_DESCRIPTION_1		0x36
+#define DETAILED_TIMING_DESCRIPTION_2		0x48
+#define DETAILED_TIMING_DESCRIPTION_3		0x5a
+#define DETAILED_TIMING_DESCRIPTION_4		0x6c
+
+#define DESCRIPTOR_DATA				5
+
+#define UPPER_NIBBLE( x ) \
+        (((128|64|32|16) & (x)) >> 4)
+
+#define LOWER_NIBBLE( x ) \
+        ((1|2|4|8) & (x))
+
+#define COMBINE_HI_8LO( hi, lo ) \
+        ( (((unsigned)hi) << 8) | (unsigned)lo )
+
+#define COMBINE_HI_4LO( hi, lo ) \
+        ( (((unsigned)hi) << 4) | (unsigned)lo )
+
+#define PIXEL_CLOCK_LO     (unsigned)block[ 0 ]
+#define PIXEL_CLOCK_HI     (unsigned)block[ 1 ]
+#define PIXEL_CLOCK	   (COMBINE_HI_8LO( PIXEL_CLOCK_HI,PIXEL_CLOCK_LO )*10000)
+#define H_ACTIVE_LO        (unsigned)block[ 2 ]
+#define H_BLANKING_LO      (unsigned)block[ 3 ]
+#define H_ACTIVE_HI        UPPER_NIBBLE( (unsigned)block[ 4 ] )
+#define H_ACTIVE           COMBINE_HI_8LO( H_ACTIVE_HI, H_ACTIVE_LO )
+#define H_BLANKING_HI      LOWER_NIBBLE( (unsigned)block[ 4 ] )
+#define H_BLANKING         COMBINE_HI_8LO( H_BLANKING_HI, H_BLANKING_LO )
+
+#define V_ACTIVE_LO        (unsigned)block[ 5 ]
+#define V_BLANKING_LO      (unsigned)block[ 6 ]
+#define V_ACTIVE_HI        UPPER_NIBBLE( (unsigned)block[ 7 ] )
+#define V_ACTIVE           COMBINE_HI_8LO( V_ACTIVE_HI, V_ACTIVE_LO )
+#define V_BLANKING_HI      LOWER_NIBBLE( (unsigned)block[ 7 ] )
+#define V_BLANKING         COMBINE_HI_8LO( V_BLANKING_HI, V_BLANKING_LO )
+
+#define H_SYNC_OFFSET_LO   (unsigned)block[ 8 ]
+#define H_SYNC_WIDTH_LO    (unsigned)block[ 9 ]
+
+#define V_SYNC_OFFSET_LO   UPPER_NIBBLE( (unsigned)block[ 10 ] )
+#define V_SYNC_WIDTH_LO    LOWER_NIBBLE( (unsigned)block[ 10 ] )
+
+#define V_SYNC_WIDTH_HI    ((unsigned)block[ 11 ] & (1|2))
+#define V_SYNC_OFFSET_HI   (((unsigned)block[ 11 ] & (4|8)) >> 2)
+
+#define H_SYNC_WIDTH_HI    (((unsigned)block[ 11 ] & (16|32)) >> 4)
+#define H_SYNC_OFFSET_HI   (((unsigned)block[ 11 ] & (64|128)) >> 6)
+
+#define V_SYNC_WIDTH       COMBINE_HI_4LO( V_SYNC_WIDTH_HI, V_SYNC_WIDTH_LO )
+#define V_SYNC_OFFSET      COMBINE_HI_4LO( V_SYNC_OFFSET_HI, V_SYNC_OFFSET_LO )
+
+#define H_SYNC_WIDTH       COMBINE_HI_8LO( H_SYNC_WIDTH_HI, H_SYNC_WIDTH_LO )
+#define H_SYNC_OFFSET      COMBINE_HI_8LO( H_SYNC_OFFSET_HI, H_SYNC_OFFSET_LO )
+
+#define H_SIZE_LO          (unsigned)block[ 12 ]
+#define V_SIZE_LO          (unsigned)block[ 13 ]
+
+#define H_SIZE_HI          UPPER_NIBBLE( (unsigned)block[ 14 ] )
+#define V_SIZE_HI          LOWER_NIBBLE( (unsigned)block[ 14 ] )
+
+#define H_SIZE             COMBINE_HI_8LO( H_SIZE_HI, H_SIZE_LO )
+#define V_SIZE             COMBINE_HI_8LO( V_SIZE_HI, V_SIZE_LO )
+
+#define H_BORDER           (unsigned)block[ 15 ]
+#define V_BORDER           (unsigned)block[ 16 ]
+
+#define FLAGS              (unsigned)block[ 17 ]
+
+#define INTERLACED         (FLAGS&128)
+#define SYNC_TYPE          (FLAGS&3<<3)	/* bits 4,3 */
+#define SYNC_SEPARATE      (3<<3)
+#define HSYNC_POSITIVE     (FLAGS & 4)
+#define VSYNC_POSITIVE     (FLAGS & 2)
+
+#define V_MIN_RATE              block[ 5 ]
+#define V_MAX_RATE              block[ 6 ]
+#define H_MIN_RATE              block[ 7 ]
+#define H_MAX_RATE              block[ 8 ]
+#define MAX_PIXEL_CLOCK         (((int)block[ 9 ]) * 10)
+#define GTF_SUPPORT		block[10]
+
+#define DPMS_ACTIVE_OFF		(1 << 5)
+#define DPMS_SUSPEND		(1 << 6)
+#define DPMS_STANDBY		(1 << 7)
+
+#endif /* __EDID_H__ */