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/arc/Makefile | 108 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 108 insertions(+) create mode 100644 arch/arc/Makefile (limited to 'arch/arc/Makefile') diff --git a/arch/arc/Makefile b/arch/arc/Makefile new file mode 100644 index 000000000..868805ffc --- /dev/null +++ b/arch/arc/Makefile @@ -0,0 +1,108 @@ +# SPDX-License-Identifier: GPL-2.0-only +# +# Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com) +# + +KBUILD_DEFCONFIG := haps_hs_smp_defconfig + +ifeq ($(CROSS_COMPILE),) +CROSS_COMPILE := $(call cc-cross-prefix, arc-linux- arceb-linux- arc-linux-gnu-) +endif + +cflags-y += -fno-common -pipe -fno-builtin -mmedium-calls -mswape -D__linux__ + +tune-mcpu-def-$(CONFIG_ISA_ARCOMPACT) := -mcpu=arc700 +tune-mcpu-def-$(CONFIG_ISA_ARCV2) := -mcpu=hs38 + +ifeq ($(CONFIG_ARC_TUNE_MCPU),) +cflags-y += $(tune-mcpu-def-y) +else +tune-mcpu := $(CONFIG_ARC_TUNE_MCPU) +ifneq ($(call cc-option,$(tune-mcpu)),) +cflags-y += $(tune-mcpu) +else +# The flag provided by 'CONFIG_ARC_TUNE_MCPU' option isn't known by this compiler +# (probably the compiler is too old). Use ISA default mcpu flag instead as a safe option. +$(warning ** WARNING ** CONFIG_ARC_TUNE_MCPU flag '$(tune-mcpu)' is unknown, fallback to '$(tune-mcpu-def-y)') +cflags-y += $(tune-mcpu-def-y) +endif +endif + +ifdef CONFIG_ARC_CURR_IN_REG +# For a global register definition, make sure it gets passed to every file +# We had a customer reported bug where some code built in kernel was NOT using +# any kernel headers, and missing the global register +# Can't do unconditionally because of recursive include issues +# due to +LINUXINCLUDE += -include $(srctree)/arch/arc/include/asm/current.h +cflags-y += -ffixed-gp +endif + +cflags-y += -fsection-anchors + +cflags-$(CONFIG_ARC_HAS_LLSC) += -mlock + +ifdef CONFIG_ISA_ARCV2 + +ifdef CONFIG_ARC_USE_UNALIGNED_MEM_ACCESS +cflags-y += -munaligned-access +else +cflags-y += -mno-unaligned-access +endif + +ifndef CONFIG_ARC_HAS_LL64 +cflags-y += -mno-ll64 +endif + +ifndef CONFIG_ARC_HAS_DIV_REM +cflags-y += -mno-div-rem +endif + +endif + +cfi := $(call as-instr,.cfi_startproc\n.cfi_endproc,-DARC_DW2_UNWIND_AS_CFI) +cflags-$(CONFIG_ARC_DW2_UNWIND) += -fasynchronous-unwind-tables $(cfi) + +# small data is default for elf32 tool-chain. If not usable, disable it +# This also allows repurposing GP as scratch reg to gcc reg allocator +disable_small_data := y +cflags-$(disable_small_data) += -mno-sdata + +cflags-$(CONFIG_CPU_BIG_ENDIAN) += -mbig-endian +ldflags-$(CONFIG_CPU_BIG_ENDIAN) += -EB + +LIBGCC = $(shell $(CC) $(cflags-y) --print-libgcc-file-name) + +# Modules with short calls might break for calls into builtin-kernel +KBUILD_CFLAGS_MODULE += -mlong-calls -mno-millicode + +# Finally dump eveything into kernel build system +KBUILD_CFLAGS += $(cflags-y) +KBUILD_AFLAGS += $(KBUILD_CFLAGS) +KBUILD_LDFLAGS += $(ldflags-y) + +core-y += arch/arc/plat-sim/ +core-$(CONFIG_ARC_PLAT_TB10X) += arch/arc/plat-tb10x/ +core-$(CONFIG_ARC_PLAT_AXS10X) += arch/arc/plat-axs10x/ +core-$(CONFIG_ARC_SOC_HSDK) += arch/arc/plat-hsdk/ + +libs-y += arch/arc/lib/ $(LIBGCC) + +boot := arch/arc/boot + +boot_targets := uImage.bin uImage.gz uImage.lzma + +PHONY += $(boot_targets) +$(boot_targets): vmlinux + $(Q)$(MAKE) $(build)=$(boot) $(boot)/$@ + +uimage-default-y := uImage.bin +uimage-default-$(CONFIG_KERNEL_GZIP) := uImage.gz +uimage-default-$(CONFIG_KERNEL_LZMA) := uImage.lzma + +PHONY += uImage +uImage: $(uimage-default-y) + @ln -sf $< $(boot)/uImage + @$(kecho) ' Image $(boot)/uImage is ready' + +CLEAN_FILES += $(boot)/uImage -- cgit v1.3.1