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, 87 insertions, 0 deletions

diff --git a/tools/testing/nvdimm/Kbuild b/tools/testing/nvdimm/Kbuild
new file mode 100644
index 000000000..91a3627f3
--- /dev/null
+++ b/tools/testing/nvdimm/Kbuild
@@ -0,0 +1,87 @@
+# SPDX-License-Identifier: GPL-2.0
+ldflags-y += --wrap=ioremap_wc
+ldflags-y += --wrap=memremap
+ldflags-y += --wrap=devm_ioremap
+ldflags-y += --wrap=devm_memremap
+ldflags-y += --wrap=devm_memunmap
+ldflags-y += --wrap=ioremap
+ldflags-y += --wrap=iounmap
+ldflags-y += --wrap=memunmap
+ldflags-y += --wrap=__devm_request_region
+ldflags-y += --wrap=__devm_release_region
+ldflags-y += --wrap=__request_region
+ldflags-y += --wrap=__release_region
+ldflags-y += --wrap=devm_memremap_pages
+ldflags-y += --wrap=insert_resource
+ldflags-y += --wrap=remove_resource
+ldflags-y += --wrap=acpi_evaluate_object
+ldflags-y += --wrap=acpi_evaluate_dsm
+
+DRIVERS := ../../../drivers
+NVDIMM_SRC := $(DRIVERS)/nvdimm
+ACPI_SRC := $(DRIVERS)/acpi/nfit
+DAX_SRC := $(DRIVERS)/dax
+ccflags-y := -I$(srctree)/drivers/nvdimm/
+ccflags-y += -I$(srctree)/drivers/acpi/nfit/
+
+obj-$(CONFIG_LIBNVDIMM) += libnvdimm.o
+obj-$(CONFIG_BLK_DEV_PMEM) += nd_pmem.o
+obj-$(CONFIG_ND_BTT) += nd_btt.o
+obj-$(CONFIG_X86_PMEM_LEGACY) += nd_e820.o
+obj-$(CONFIG_ACPI_NFIT) += nfit.o
+ifeq ($(CONFIG_DAX),m)
+obj-$(CONFIG_DAX) += dax.o
+endif
+obj-$(CONFIG_DEV_DAX) += device_dax.o
+obj-$(CONFIG_DEV_DAX_PMEM) += dax_pmem.o
+
+nfit-y := $(ACPI_SRC)/core.o
+nfit-y += $(ACPI_SRC)/intel.o
+nfit-$(CONFIG_X86_MCE) += $(ACPI_SRC)/mce.o
+nfit-y += acpi_nfit_test.o
+nfit-y += config_check.o
+
+nd_pmem-y := $(NVDIMM_SRC)/pmem.o
+nd_pmem-y += pmem-dax.o
+nd_pmem-y += pmem_test.o
+nd_pmem-y += config_check.o
+
+nd_btt-y := $(NVDIMM_SRC)/btt.o
+nd_btt-y += config_check.o
+
+nd_e820-y := $(NVDIMM_SRC)/e820.o
+nd_e820-y += config_check.o
+
+dax-y := $(DAX_SRC)/super.o
+dax-y += $(DAX_SRC)/bus.o
+dax-y += config_check.o
+
+device_dax-y := $(DAX_SRC)/device.o
+device_dax-y += dax-dev.o
+device_dax-y += device_dax_test.o
+device_dax-y += config_check.o
+
+dax_pmem-y := $(DAX_SRC)/pmem.o
+dax_pmem-y += dax_pmem_test.o
+dax_pmem-y += config_check.o
+
+libnvdimm-y := $(NVDIMM_SRC)/core.o
+libnvdimm-y += $(NVDIMM_SRC)/bus.o
+libnvdimm-y += $(NVDIMM_SRC)/dimm_devs.o
+libnvdimm-y += $(NVDIMM_SRC)/dimm.o
+libnvdimm-y += $(NVDIMM_SRC)/region_devs.o
+libnvdimm-y += $(NVDIMM_SRC)/region.o
+libnvdimm-y += $(NVDIMM_SRC)/namespace_devs.o
+libnvdimm-y += $(NVDIMM_SRC)/label.o
+libnvdimm-y += $(NVDIMM_SRC)/badrange.o
+libnvdimm-$(CONFIG_ND_CLAIM) += $(NVDIMM_SRC)/claim.o
+libnvdimm-$(CONFIG_BTT) += $(NVDIMM_SRC)/btt_devs.o
+libnvdimm-$(CONFIG_NVDIMM_PFN) += $(NVDIMM_SRC)/pfn_devs.o
+libnvdimm-$(CONFIG_NVDIMM_DAX) += $(NVDIMM_SRC)/dax_devs.o
+libnvdimm-$(CONFIG_NVDIMM_KEYS) += $(NVDIMM_SRC)/security.o
+libnvdimm-y += libnvdimm_test.o
+libnvdimm-y += config_check.o
+
+KBUILD_CFLAGS := $(filter-out -Wmissing-prototypes -Wmissing-declarations, $(KBUILD_CFLAGS))
+
+obj-m += test/