From 0d6526f82c3cdefcca47f73f5fc08dc6f335eac6 Mon Sep 17 00:00:00 2001 From: Tim Chen Date: Mon, 21 Sep 2026 17:37:22 -0700 Subject: sched/cache: Keep nr_pref_llc_running in the runnable domain, to fix LLC mis-scheduling bug 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 Suggested-by: Chen Yu Signed-off-by: Tim Chen Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Reviewed-by: Kayra Cizmeci Cc: # v7.2.x Link: https://patch.msgid.link/06af61afedac32e6477f57feb4d658f6c411c3af.1790035273.git.tim.c.chen@linux.intel.com --- arch/xtensa/Makefile | 77 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 77 insertions(+) create mode 100644 arch/xtensa/Makefile (limited to 'arch/xtensa/Makefile') diff --git a/arch/xtensa/Makefile b/arch/xtensa/Makefile new file mode 100644 index 000000000..4c14a0217 --- /dev/null +++ b/arch/xtensa/Makefile @@ -0,0 +1,77 @@ +# +# 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. +# +# Copyright (C) 2001 - 2005 Tensilica Inc. +# Copyright (C) 2014 Cadence Design Systems Inc. +# +# This file is included by the global makefile so that you can add your own +# architecture-specific flags and dependencies. + +# Core configuration. +# (Use VAR= to use another default compiler.) + +variant-y := $(CONFIG_XTENSA_VARIANT_NAME) + +VARIANT = $(variant-y) + +ifneq ($(VARIANT),) + ifdef cross_compiling + ifndef CROSS_COMPILE + CROSS_COMPILE = xtensa_$(VARIANT)- + endif + endif +endif + +# Platform configuration + +platform-$(CONFIG_XTENSA_PLATFORM_XT2000) := xt2000 +platform-$(CONFIG_XTENSA_PLATFORM_ISS) := iss +platform-$(CONFIG_XTENSA_PLATFORM_XTFPGA) := xtfpga + +# temporarily until string.h is fixed +KBUILD_CFLAGS += -ffreestanding -D__linux__ +KBUILD_CFLAGS += -pipe -mlongcalls -mtext-section-literals +KBUILD_CFLAGS += $(call cc-option,-mforce-no-pic,) +KBUILD_CFLAGS += $(call cc-option,-mno-serialize-volatile,) +KBUILD_CFLAGS += $(call cc-option,-mno-fdpic,) +ifneq ($(CONFIG_KERNEL_ABI_CALL0),) +KBUILD_CFLAGS += -mabi=call0 +KBUILD_AFLAGS += -mabi=call0 +endif + +KBUILD_AFLAGS += -mlongcalls -mtext-section-literals +KBUILD_AFLAGS += $(call cc-option,-mno-fdpic,) + +KBUILD_LDFLAGS += -m elf32xtensa + +ifneq ($(CONFIG_LD_NO_RELAX),) +KBUILD_LDFLAGS += --no-relax +endif + +CHECKFLAGS += -D$(if $(CONFIG_CPU_BIG_ENDIAN),__XTENSA_EB__,__XTENSA_EL__) + +vardirs := $(patsubst %,arch/xtensa/variants/%/,$(variant-y)) +plfdirs := $(patsubst %,arch/xtensa/platforms/%/,$(platform-y)) + +KBUILD_CPPFLAGS += $(patsubst %,-I$(srctree)/%include,$(vardirs) $(plfdirs)) + +KBUILD_DEFCONFIG := iss_defconfig + +libs-y += arch/xtensa/lib/ + +boot := arch/xtensa/boot + +all Image zImage uImage xipImage: vmlinux + $(Q)$(MAKE) $(build)=$(boot) $@ + +archheaders: + $(Q)$(MAKE) $(build)=arch/xtensa/kernel/syscalls all + +define archhelp + @echo '* Image - Kernel ELF image with reset vector' + @echo '* zImage - Compressed kernel image (arch/xtensa/boot/images/zImage.*)' + @echo '* uImage - U-Boot wrapped image' + @echo ' xipImage - XIP image' +endef -- cgit v1.3.1