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, 173 insertions, 0 deletions

diff --git a/drivers/usb/serial/usb-serial-simple.c b/drivers/usb/serial/usb-serial-simple.c
new file mode 100644
index 000000000..a0afaf254
--- /dev/null
+++ b/drivers/usb/serial/usb-serial-simple.c
@@ -0,0 +1,173 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * USB Serial "Simple" driver
+ *
+ * Copyright (C) 2001-2006,2008,2013 Greg Kroah-Hartman <greg@kroah.com>
+ * Copyright (C) 2005 Arthur Huillet (ahuillet@users.sf.net)
+ * Copyright (C) 2005 Thomas Hergenhahn <thomas.hergenhahn@suse.de>
+ * Copyright (C) 2009 Outpost Embedded, LLC
+ * Copyright (C) 2010 Zilogic Systems <code@zilogic.com>
+ * Copyright (C) 2013 Wei Shuai <cpuwolf@gmail.com>
+ * Copyright (C) 2013 Linux Foundation
+ */
+
+#include <linux/kernel.h>
+#include <linux/tty.h>
+#include <linux/module.h>
+#include <linux/usb.h>
+#include <linux/usb/serial.h>
+
+#define DEVICE_N(vendor, IDS, nport)				\
+static const struct usb_device_id vendor##_id_table[] = {	\
+	IDS(),							\
+	{ },							\
+};								\
+static struct usb_serial_driver vendor##_device = {		\
+	.driver = {						\
+		.name =		#vendor,			\
+	},							\
+	.id_table =		vendor##_id_table,		\
+	.num_ports =		nport,				\
+};
+
+#define DEVICE(vendor, IDS)	DEVICE_N(vendor, IDS, 1)
+
+/* Medtronic CareLink USB driver */
+#define CARELINK_IDS()			\
+	{ USB_DEVICE(0x0a21, 0x8001) }	/* MMT-7305WW */
+DEVICE(carelink, CARELINK_IDS);
+
+/* Infineon Flashloader driver */
+#define FLASHLOADER_IDS()		\
+	{ USB_DEVICE_INTERFACE_CLASS(0x058b, 0x0041, USB_CLASS_CDC_DATA) }, \
+	{ USB_DEVICE(0x8087, 0x0716) }, \
+	{ USB_DEVICE(0x8087, 0x0801) }
+DEVICE(flashloader, FLASHLOADER_IDS);
+
+/* Funsoft Serial USB driver */
+#define FUNSOFT_IDS()			\
+	{ USB_DEVICE(0x1404, 0xcddc) }
+DEVICE(funsoft, FUNSOFT_IDS);
+
+/* Google Serial USB SubClass */
+#define GOOGLE_IDS()						\
+	{ USB_VENDOR_AND_INTERFACE_INFO(0x18d1,			\
+					USB_CLASS_VENDOR_SPEC,	\
+					0x50,			\
+					0x01) }
+DEVICE(google, GOOGLE_IDS);
+
+/* HP4x (48/49) Generic Serial driver */
+#define HP4X_IDS()			\
+	{ USB_DEVICE(0x03f0, 0x0121) }
+DEVICE(hp4x, HP4X_IDS);
+
+/* KAUFMANN RKS+CAN VCP */
+#define KAUFMANN_IDS()			\
+	{ USB_DEVICE(0x16d0, 0x0870) }
+DEVICE(kaufmann, KAUFMANN_IDS);
+
+/* Libtransistor USB console */
+#define LIBTRANSISTOR_IDS()			\
+	{ USB_DEVICE(0x1209, 0x8b00) }
+DEVICE(libtransistor, LIBTRANSISTOR_IDS);
+
+/* Motorola USB Phone driver */
+#define MOTO_IDS()			\
+	{ USB_DEVICE(0x05c6, 0x3197) },	/* unknown Motorola phone */	\
+	{ USB_DEVICE(0x0c44, 0x0022) },	/* unknown Motorola phone */	\
+	{ USB_DEVICE(0x22b8, 0x2a64) },	/* Motorola KRZR K1m */		\
+	{ USB_DEVICE(0x22b8, 0x2c84) },	/* Motorola VE240 phone */	\
+	{ USB_DEVICE(0x22b8, 0x2c64) }	/* Motorola V950 phone */
+DEVICE(moto_modem, MOTO_IDS);
+
+/* Motorola Tetra driver */
+#define MOTOROLA_TETRA_IDS()			\
+	{ USB_DEVICE(0x0cad, 0x9011) },	/* Motorola Solutions TETRA PEI */ \
+	{ USB_DEVICE(0x0cad, 0x9012) },	/* MTP6550 */ \
+	{ USB_DEVICE(0x0cad, 0x9013) },	/* MTP3xxx */ \
+	{ USB_DEVICE(0x0cad, 0x9015) },	/* MTP85xx */ \
+	{ USB_DEVICE(0x0cad, 0x9016) }	/* TPG2200 */
+DEVICE(motorola_tetra, MOTOROLA_TETRA_IDS);
+
+/* Nokia mobile phone driver */
+#define NOKIA_IDS()			\
+	{ USB_DEVICE(0x0421, 0x069a) }	/* Nokia 130 (RM-1035) */
+DEVICE(nokia, NOKIA_IDS);
+
+/* Novatel Wireless GPS driver */
+#define NOVATEL_IDS()			\
+	{ USB_DEVICE(0x09d7, 0x0100) }	/* NovAtel FlexPack GPS */
+DEVICE_N(novatel_gps, NOVATEL_IDS, 3);
+
+/* OWON electronic test and measurement equipment driver */
+#define OWON_IDS()			\
+	{ USB_DEVICE(0x5345, 0x1234) } /* HDS200 oscilloscopes and others */
+DEVICE(owon, OWON_IDS);
+
+/* Siemens USB/MPI adapter */
+#define SIEMENS_IDS()			\
+	{ USB_DEVICE(0x908, 0x0004) }
+DEVICE(siemens_mpi, SIEMENS_IDS);
+
+/* Suunto ANT+ USB Driver */
+#define SUUNTO_IDS()			\
+	{ USB_DEVICE(0x0fcf, 0x1008) },	\
+	{ USB_DEVICE(0x0fcf, 0x1009) } /* Dynastream ANT USB-m Stick */
+DEVICE(suunto, SUUNTO_IDS);
+
+/* ViVOpay USB Serial Driver */
+#define VIVOPAY_IDS()			\
+	{ USB_DEVICE(0x1d5f, 0x1004) }	/* ViVOpay 8800 */
+DEVICE(vivopay, VIVOPAY_IDS);
+
+/* ZIO Motherboard USB driver */
+#define ZIO_IDS()			\
+	{ USB_DEVICE(0x1CBE, 0x0103) }
+DEVICE(zio, ZIO_IDS);
+
+/* All of the above structures mushed into two lists */
+static struct usb_serial_driver * const serial_drivers[] = {
+	&carelink_device,
+	&flashloader_device,
+	&funsoft_device,
+	&google_device,
+	&hp4x_device,
+	&kaufmann_device,
+	&libtransistor_device,
+	&moto_modem_device,
+	&motorola_tetra_device,
+	&nokia_device,
+	&novatel_gps_device,
+	&owon_device,
+	&siemens_mpi_device,
+	&suunto_device,
+	&vivopay_device,
+	&zio_device,
+	NULL
+};
+
+static const struct usb_device_id id_table[] = {
+	CARELINK_IDS(),
+	FLASHLOADER_IDS(),
+	FUNSOFT_IDS(),
+	GOOGLE_IDS(),
+	HP4X_IDS(),
+	KAUFMANN_IDS(),
+	LIBTRANSISTOR_IDS(),
+	MOTO_IDS(),
+	MOTOROLA_TETRA_IDS(),
+	NOKIA_IDS(),
+	NOVATEL_IDS(),
+	OWON_IDS(),
+	SIEMENS_IDS(),
+	SUUNTO_IDS(),
+	VIVOPAY_IDS(),
+	ZIO_IDS(),
+	{ },
+};
+MODULE_DEVICE_TABLE(usb, id_table);
+
+module_usb_serial_driver(serial_drivers, id_table);
+MODULE_DESCRIPTION("USB Serial 'Simple' driver");
+MODULE_LICENSE("GPL v2");