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/boot/boot-elf/.gitignore | 2 + arch/xtensa/boot/boot-elf/Makefile | 30 +++++++++++++ arch/xtensa/boot/boot-elf/boot.lds.S | 40 ++++++++++++++++++ arch/xtensa/boot/boot-elf/bootstrap.S | 79 +++++++++++++++++++++++++++++++++++ 4 files changed, 151 insertions(+) create mode 100644 arch/xtensa/boot/boot-elf/.gitignore create mode 100644 arch/xtensa/boot/boot-elf/Makefile create mode 100644 arch/xtensa/boot/boot-elf/boot.lds.S create mode 100644 arch/xtensa/boot/boot-elf/bootstrap.S (limited to 'arch/xtensa/boot/boot-elf') diff --git a/arch/xtensa/boot/boot-elf/.gitignore b/arch/xtensa/boot/boot-elf/.gitignore new file mode 100644 index 000000000..747340450 --- /dev/null +++ b/arch/xtensa/boot/boot-elf/.gitignore @@ -0,0 +1,2 @@ +# SPDX-License-Identifier: GPL-2.0-only +boot.lds diff --git a/arch/xtensa/boot/boot-elf/Makefile b/arch/xtensa/boot/boot-elf/Makefile new file mode 100644 index 000000000..faec20029 --- /dev/null +++ b/arch/xtensa/boot/boot-elf/Makefile @@ -0,0 +1,30 @@ +# +# 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. +# + +OBJCOPY_ARGS := -O $(if $(CONFIG_CPU_BIG_ENDIAN),elf32-xtensa-be,elf32-xtensa-le) + +CPPFLAGS_boot.lds += -P -C +KBUILD_AFLAGS += -mtext-section-literals + +boot-y := bootstrap.o +targets += $(boot-y) boot.lds + +OBJS := $(addprefix $(obj)/,$(boot-y)) + +$(obj)/Image.o: $(obj)/../vmlinux.bin $(OBJS) + $(Q)$(OBJCOPY) $(OBJCOPY_ARGS) -R .comment \ + --add-section image=$< \ + --set-section-flags image=contents,alloc,load,load,data \ + $(OBJS) $@ + +$(obj)/../Image.elf: $(obj)/Image.o $(obj)/boot.lds + $(Q)$(LD) $(KBUILD_LDFLAGS) \ + -T $(obj)/boot.lds \ + --build-id=none \ + -o $@ $(obj)/Image.o + $(Q)$(kecho) ' Kernel: $@ is ready' + +all Image: $(obj)/../Image.elf diff --git a/arch/xtensa/boot/boot-elf/boot.lds.S b/arch/xtensa/boot/boot-elf/boot.lds.S new file mode 100644 index 000000000..32a3b7c5b --- /dev/null +++ b/arch/xtensa/boot/boot-elf/boot.lds.S @@ -0,0 +1,40 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * linux/arch/xtensa/boot/boot-elf/boot.lds.S + * + * Copyright (C) 2008 - 2013 by Tensilica Inc. + * + * Chris Zankel + * Marc Gauthier + */ + +#include +OUTPUT_ARCH(xtensa) +ENTRY(_ResetVector) + +SECTIONS +{ + .ResetVector.text XCHAL_RESET_VECTOR_VADDR : + { + *(.ResetVector.text) + } + + .image KERNELOFFSET: AT (CONFIG_KERNEL_LOAD_ADDRESS) + { + _image_start = .; + *(image) + . = (. + 3) & ~ 3; + _image_end = . ; + } + + .bss ((LOADADDR(.image) + SIZEOF(.image) + 3) & ~ 3): + { + __bss_start = .; + *(.sbss) + *(.scommon) + *(.dynbss) + *(.bss) + __bss_end = .; + } +} diff --git a/arch/xtensa/boot/boot-elf/bootstrap.S b/arch/xtensa/boot/boot-elf/bootstrap.S new file mode 100644 index 000000000..2dd28931d --- /dev/null +++ b/arch/xtensa/boot/boot-elf/bootstrap.S @@ -0,0 +1,79 @@ +/* + * arch/xtensa/boot/boot-elf/bootstrap.S + * + * Low-level exception handling + * + * 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) 2004 - 2013 by Tensilica Inc. + * + * Chris Zankel + * Marc Gauthier + * Piet Delaney + */ + +#include +#include +#include +#include + + .section .ResetVector.text, "ax" + .global _ResetVector + .global reset + +_ResetVector: + _j _SetupMMU + + .begin no-absolute-literals + .literal_position + +#ifdef CONFIG_PARSE_BOOTPARAM + .align 4 +_bootparam: + .short BP_TAG_FIRST + .short 4 + .long BP_VERSION + .short BP_TAG_LAST + .short 0 + .long 0 +#endif + + .align 4 +_SetupMMU: +#if XCHAL_HAVE_WINDOWED + movi a0, 0 + wsr a0, windowbase + rsync + movi a0, 1 + wsr a0, windowstart + rsync +#endif + movi a0, 0x1F + wsr a0, ps + rsync + +#ifndef CONFIG_INITIALIZE_XTENSA_MMU_INSIDE_VMLINUX + initialize_mmu +#endif + + rsil a0, XCHAL_DEBUGLEVEL-1 + rsync +reset: +#if defined(CONFIG_INITIALIZE_XTENSA_MMU_INSIDE_VMLINUX) && \ + XCHAL_HAVE_PTP_MMU && XCHAL_HAVE_SPANNING_WAY + movi a0, CONFIG_KERNEL_LOAD_ADDRESS +#else + movi a0, KERNELOFFSET +#endif +#ifdef CONFIG_PARSE_BOOTPARAM + movi a2, _bootparam +#else + movi a2, 0 +#endif + movi a3, 0 + movi a4, 0 + jx a0 + + .end no-absolute-literals -- cgit v1.3.1