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, 117 insertions, 0 deletions

diff --git a/drivers/phy/broadcom/Kconfig b/drivers/phy/broadcom/Kconfig
new file mode 100644
index 000000000..46371a894
--- /dev/null
+++ b/drivers/phy/broadcom/Kconfig
@@ -0,0 +1,117 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Phy drivers for Broadcom platforms
+#
+menu "PHY drivers for Broadcom platforms"
+
+config PHY_BCM63XX_USBH
+	tristate "BCM63xx USBH PHY driver"
+	depends on BMIPS_GENERIC || COMPILE_TEST
+	select GENERIC_PHY
+	help
+	  Enable this to support the BCM63xx USBH PHY driver.
+	  If unsure, say N.
+
+config PHY_CYGNUS_PCIE
+	tristate "Broadcom Cygnus PCIe PHY driver"
+	depends on OF && (ARCH_BCM_CYGNUS || COMPILE_TEST)
+	select GENERIC_PHY
+	default ARCH_BCM_CYGNUS
+	help
+	  Enable this to support the Broadcom Cygnus PCIe PHY.
+	  If unsure, say N.
+
+config PHY_BCM_SR_USB
+	tristate "Broadcom Stingray USB PHY driver"
+	depends on OF && (ARCH_BCM_IPROC || COMPILE_TEST)
+	select GENERIC_PHY
+	default ARCH_BCM_IPROC
+	help
+	  Enable this to support the Broadcom Stingray USB PHY
+	  driver. It supports all versions of Superspeed and
+	  Highspeed PHYs.
+	  If unsure, say N.
+
+config BCM_KONA_USB2_PHY
+	tristate "Broadcom Kona USB2 PHY Driver"
+	depends on HAS_IOMEM
+	select GENERIC_PHY
+	help
+	  Enable this to support the Broadcom Kona USB 2.0 PHY.
+
+config PHY_BCM_NS_USB2
+	tristate "Broadcom Northstar USB 2.0 PHY Driver"
+	depends on ARCH_BCM_IPROC || COMPILE_TEST
+	depends on HAS_IOMEM && OF
+	select GENERIC_PHY
+	help
+	  Enable this to support Broadcom USB 2.0 PHY connected to the USB
+	  controller on Northstar family.
+
+config PHY_BCM_NS_USB3
+	tristate "Broadcom Northstar USB 3.0 PHY Driver"
+	depends on ARCH_BCM_IPROC || COMPILE_TEST
+	depends on HAS_IOMEM && OF
+	depends on PHYLIB
+	select GENERIC_PHY
+	help
+	  Enable this to support Broadcom USB 3.0 PHY connected to the USB
+	  controller on Northstar family.
+
+config PHY_NS2_PCIE
+	tristate "Broadcom Northstar2 PCIe PHY driver"
+	depends on (OF && MDIO_BUS_MUX_BCM_IPROC) || (COMPILE_TEST && PHYLIB)
+	select GENERIC_PHY
+	default ARCH_BCM_IPROC
+	help
+	  Enable this to support the Broadcom Northstar2 PCIe PHY.
+	  If unsure, say N.
+
+config PHY_NS2_USB_DRD
+	tristate "Broadcom Northstar2 USB DRD PHY support"
+	depends on OF && (ARCH_BCM_IPROC || COMPILE_TEST)
+	select GENERIC_PHY
+	select EXTCON
+	default ARCH_BCM_IPROC
+	help
+	  Enable this to support the Broadcom Northstar2 USB DRD PHY.
+	  This driver initializes the PHY in either HOST or DEVICE mode.
+	  The host or device configuration is read from device tree.
+
+	  If unsure, say N.
+
+config PHY_BRCM_SATA
+	tristate "Broadcom SATA PHY driver"
+	depends on ARCH_BRCMSTB || ARCH_BCM_IPROC || BMIPS_GENERIC || \
+		   ARCH_BCMBCA || COMPILE_TEST
+	depends on OF
+	select GENERIC_PHY
+	default ARCH_BCM_IPROC
+	help
+	  Enable this to support the Broadcom SATA PHY.
+	  If unsure, say N.
+
+config PHY_BRCM_USB
+	tristate "Broadcom STB USB PHY driver"
+	depends on ARCH_BCMBCA || ARCH_BRCMSTB || COMPILE_TEST
+	depends on OF
+	select GENERIC_PHY
+	select SOC_BRCMSTB if ARCH_BRCMSTB
+	default ARCH_BCMBCA || ARCH_BRCMSTB
+	help
+	  Enable this to support the Broadcom STB USB PHY.
+	  This driver is required by the USB XHCI, EHCI and OHCI
+	  drivers.
+	  If unsure, say N.
+
+config PHY_BCM_SR_PCIE
+	tristate "Broadcom Stingray PCIe PHY driver"
+	depends on OF && (ARCH_BCM_IPROC || COMPILE_TEST)
+	select GENERIC_PHY
+	select MFD_SYSCON
+	default ARCH_BCM_IPROC
+	help
+	  Enable this to support the Broadcom Stingray PCIe PHY
+	  If unsure, say N.
+
+endmenu