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/Makefile | 53 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 53 insertions(+) create mode 100644 arch/xtensa/boot/Makefile (limited to 'arch/xtensa/boot/Makefile') diff --git a/arch/xtensa/boot/Makefile b/arch/xtensa/boot/Makefile new file mode 100644 index 000000000..d8b0fadf4 --- /dev/null +++ b/arch/xtensa/boot/Makefile @@ -0,0 +1,53 @@ +# +# arch/xtensa/boot/Makefile +# +# 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. +# +# + + +# KBUILD_CFLAGS used when building rest of boot (takes effect recursively) +KBUILD_CFLAGS += -fno-builtin + +subdir-y := lib +targets += vmlinux.bin vmlinux.bin.gz +targets += uImage xipImage + +# Subdirs for the boot loader(s) + +boot-$(CONFIG_XTENSA_PLATFORM_ISS) += Image +boot-$(CONFIG_XTENSA_PLATFORM_XT2000) += Image zImage uImage +boot-$(CONFIG_XTENSA_PLATFORM_XTFPGA) += Image zImage uImage + +all: $(boot-y) +Image: boot-elf +zImage: boot-redboot +uImage: $(obj)/uImage +xipImage: $(obj)/xipImage + +boot-elf boot-redboot: $(addprefix $(obj)/,$(subdir-y)) + $(Q)$(MAKE) $(build)=$(obj)/$@ $(MAKECMDGOALS) + +OBJCOPYFLAGS = --strip-all -R .comment -R .notes -O binary + +$(obj)/vmlinux.bin: vmlinux FORCE + $(call if_changed,objcopy) + +$(obj)/vmlinux.bin.gz: $(obj)/vmlinux.bin FORCE + $(call if_changed,gzip) + +boot-elf: $(obj)/vmlinux.bin +boot-redboot: $(obj)/vmlinux.bin.gz + +UIMAGE_LOADADDR = $(CONFIG_KERNEL_LOAD_ADDRESS) +UIMAGE_COMPRESSION = gzip + +$(obj)/uImage: $(obj)/vmlinux.bin.gz FORCE + $(call if_changed,uimage) + $(Q)$(kecho) ' Kernel: $@ is ready' + +$(obj)/xipImage: vmlinux FORCE + $(call if_changed,objcopy) + $(Q)$(kecho) ' Kernel: $@ is ready' -- cgit v1.3.1