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 --- scripts/Makefile.asm-headers | 105 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 105 insertions(+) create mode 100644 scripts/Makefile.asm-headers (limited to 'scripts/Makefile.asm-headers') diff --git a/scripts/Makefile.asm-headers b/scripts/Makefile.asm-headers new file mode 100644 index 000000000..f1c3d287c --- /dev/null +++ b/scripts/Makefile.asm-headers @@ -0,0 +1,105 @@ +# SPDX-License-Identifier: GPL-2.0 +# include/asm-generic contains a lot of files that are used +# verbatim by several architectures. +# +# This Makefile generates arch/$(SRCARCH)/include/generated/(uapi/)/asm +# headers from multiple sources: +# - a small wrapper to include the corresponding asm-generic/*.h +# is generated for each file listed as generic-y +# - uapi/asm/unistd_*.h files listed as syscalls-y are generated from +# syscall.tbl with the __NR_* macros +# - Corresponding asm/syscall_table_*.h are generated from the same input + +PHONY := all +all: + +src := $(srctree)/$(subst /generated,,$(obj)) + +syscall_abis_32 += common,32 +syscall_abis_64 += common,64 +syscalltbl := $(srctree)/scripts/syscall.tbl +syshdr-args := --emit-nr + +# let architectures override $(syscall_abis_%) and $(syscalltbl) +-include $(srctree)/arch/$(SRCARCH)/kernel/Makefile.syscalls +include $(srctree)/scripts/Kbuild.include +-include $(kbuild-file) + +syshdr := $(srctree)/scripts/syscallhdr.sh +systbl := $(srctree)/scripts/syscalltbl.sh + +# $(generic)/Kbuild lists mandatory-y. Exclude um since it is a special case. +ifneq ($(SRCARCH),um) +include $(srctree)/$(generic)/Kbuild +endif + +redundant := $(filter $(mandatory-y) $(generated-y), $(generic-y)) +redundant += $(foreach f, $(generic-y), $(if $(wildcard $(src)/$(f)),$(f))) +redundant := $(sort $(redundant)) +$(if $(redundant),\ + $(warning redundant generic-y found in $(src)/Kbuild: $(redundant))) + +# If arch does not implement mandatory headers, fallback to asm-generic ones. +mandatory-y := $(filter-out $(generated-y), $(mandatory-y)) +generic-y += $(foreach f, $(mandatory-y), $(if $(wildcard $(src)/$(f)),,$(f))) + +generic-y := $(addprefix $(obj)/, $(generic-y)) +syscall-y := $(addprefix $(obj)/, $(syscall-y)) +generated-y := $(addprefix $(obj)/, $(generated-y)) + +# Remove stale wrappers when the corresponding files are removed from generic-y +old-headers := $(shell test -d $(obj) && find $(obj) -name '*.h' ! -name '.*') +unwanted := $(filter-out $(generic-y) $(generated-y) $(syscall-y),$(old-headers)) + +filechk_wrap = echo "\#include " + +quiet_cmd_remove = REMOVE $(unwanted) + cmd_remove = rm -f $(unwanted); find $(obj) -type d -empty -delete + +quiet_cmd_syshdr = SYSHDR $@ + cmd_syshdr = $(CONFIG_SHELL) $(syshdr) \ + $(if $(syshdr-args-$*),$(syshdr-args-$*),$(syshdr-args)) \ + $(if $(syscall_compat),--prefix "compat$*_") \ + --abis $(subst $(space),$(comma),$(strip $(syscall_abis_$*))) \ + $< $@ + +quiet_cmd_systbl = SYSTBL $@ + cmd_systbl = $(CONFIG_SHELL) $(systbl) \ + $(if $(systbl-args-$*),$(systbl-args-$*),$(systbl-args)) \ + --abis $(subst $(space),$(comma),$(strip $(syscall_abis_$*))) \ + $< $@ + +all: $(generic-y) $(syscall-y) + $(if $(unwanted),$(call cmd,remove)) + @: + +$(obj)/%.h: $(srctree)/$(generic)/%.h FORCE + $(call filechk,wrap) + +$(obj)/unistd_%.h: $(syscalltbl) $(syshdr) FORCE + $(call if_changed,syshdr) + +$(obj)/unistd_compat_%.h: syscall_compat:=1 +$(obj)/unistd_compat_%.h: $(syscalltbl) $(syshdr) FORCE + $(call if_changed,syshdr) + +$(obj)/syscall_table_%.h: $(syscalltbl) $(systbl) FORCE + $(call if_changed,systbl) + +targets := $(syscall-y) + +# Create output directory. Skip it if at least one old header exists +# since we know the output directory already exists. +ifeq ($(old-headers),) +$(shell mkdir -p $(obj)) +endif + +PHONY += FORCE + +FORCE: + +existing-targets := $(wildcard $(sort $(targets))) + +-include $(foreach f,$(existing-targets),$(dir $(f)).$(notdir $(f)).cmd) + +.PHONY: $(PHONY) -- cgit v1.3.1