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/arm/tools/Makefile | 57 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 57 insertions(+) create mode 100644 arch/arm/tools/Makefile (limited to 'arch/arm/tools/Makefile') diff --git a/arch/arm/tools/Makefile b/arch/arm/tools/Makefile new file mode 100644 index 000000000..28b6da8ac --- /dev/null +++ b/arch/arm/tools/Makefile @@ -0,0 +1,57 @@ +# SPDX-License-Identifier: GPL-2.0 +# +# linux/arch/arm/tools/Makefile +# +# Copyright (C) 2001 Russell King +# + +gen := arch/$(ARCH)/include/generated +kapi := $(gen)/asm +uapi := $(gen)/uapi/asm +syshdr := $(srctree)/scripts/syscallhdr.sh +sysnr := $(src)/syscallnr.sh +systbl := $(srctree)/scripts/syscalltbl.sh +syscall := $(src)/syscall.tbl + +gen-y := $(gen)/calls-oabi.S +gen-y += $(gen)/calls-eabi.S +kapi-hdrs-y := $(kapi)/unistd-nr.h +kapi-hdrs-y += $(kapi)/mach-types.h +uapi-hdrs-y += $(uapi)/unistd-oabi.h +uapi-hdrs-y += $(uapi)/unistd-eabi.h + +targets += $(addprefix ../../../,$(gen-y) $(kapi-hdrs-y) $(uapi-hdrs-y)) + +PHONY += kapi uapi + +kapi: $(kapi-hdrs-y) $(gen-y) + +uapi: $(uapi-hdrs-y) + +# Create output directory if not already present +$(shell mkdir -p $(kapi) $(uapi)) + +quiet_cmd_gen_mach = GEN $@ + cmd_gen_mach = $(AWK) -f $(real-prereqs) > $@ + +$(kapi)/mach-types.h: $(src)/gen-mach-types $(src)/mach-types FORCE + $(call if_changed,gen_mach) + +quiet_cmd_syshdr = SYSHDR $@ + cmd_syshdr = $(CONFIG_SHELL) $(syshdr) --abis common,$* \ + --offset __NR_SYSCALL_BASE $< $@ + +quiet_cmd_systbl = SYSTBL $@ + cmd_systbl = $(CONFIG_SHELL) $(systbl) --abis common,$* $< $@ + +quiet_cmd_sysnr = SYSNR $@ + cmd_sysnr = $(CONFIG_SHELL) $(sysnr) $< $@ + +$(uapi)/unistd-%.h: $(syscall) $(syshdr) FORCE + $(call if_changed,syshdr) + +$(kapi)/unistd-nr.h: $(syscall) $(sysnr) FORCE + $(call if_changed,sysnr) + +$(gen)/calls-%.S: $(syscall) $(systbl) FORCE + $(call if_changed,systbl) -- cgit v1.3.1