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.modpost | 157 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 157 insertions(+) create mode 100644 scripts/Makefile.modpost (limited to 'scripts/Makefile.modpost') diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost new file mode 100644 index 000000000..d7d45067d --- /dev/null +++ b/scripts/Makefile.modpost @@ -0,0 +1,157 @@ +# SPDX-License-Identifier: GPL-2.0 +# =========================================================================== +# Module versions +# =========================================================================== +# +# Stage one of module building created the following: +# a) The individual .o files used for the module +# b) A .o file which is the .o files above linked together +# c) A .mod file, listing the name of the preliminary .o file, +# plus all .o files +# d) modules.order, which lists all the modules + +# Stage 2 is handled by this file and does the following +# 1) Find all modules listed in modules.order +# 2) modpost is then used to +# 3) create one .mod.c file per module +# 4) create one Module.symvers file with CRC for all exported symbols + +# Step 3 is used to place certain information in the module's ELF +# section, including information such as: +# Version magic (see include/linux/vermagic.h for full details) +# - Kernel release +# - SMP is CONFIG_SMP +# - PREEMPT is CONFIG_PREEMPT[_RT] +# - GCC Version +# Module info +# - Module version (MODULE_VERSION) +# - Module alias'es (MODULE_ALIAS) +# - Module license (MODULE_LICENSE) +# - See include/linux/module.h for more details + +# Step 4 is solely used to allow module versioning in external modules, +# where the CRC of each module is retrieved from the Module.symvers file. + +PHONY := __modpost +__modpost: + +include $(objtree)/include/config/auto.conf +include $(srctree)/scripts/Kbuild.include + +MODPOST = $(objtree)/scripts/mod/modpost + +modpost-args = \ + $(if $(CONFIG_MODULES),-M) \ + $(if $(CONFIG_MODVERSIONS),-m) \ + $(if $(CONFIG_BASIC_MODVERSIONS),-b) \ + $(if $(CONFIG_EXTENDED_MODVERSIONS),-x) \ + $(if $(CONFIG_MODULE_SRCVERSION_ALL),-a) \ + $(if $(CONFIG_SECTION_MISMATCH_WARN_ONLY),,-E) \ + $(if $(KBUILD_MODPOST_WARN),-w) \ + $(if $(KBUILD_NSDEPS),-d modules.nsdeps) \ + $(if $(CONFIG_MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS)$(KBUILD_NSDEPS),-N) \ + $(if $(findstring 1, $(KBUILD_EXTRA_WARN)),-W) \ + -o $@ + +modpost-deps := $(MODPOST) + +# 'make -i -k' ignores compile errors, and builds as many modules as possible. +ifneq ($(findstring i,$(filter-out --%,$(MAKEFLAGS))),) +modpost-args += -n +endif + +# Read out modules.order to pass in modpost. +# Otherwise, allmodconfig would fail with "Argument list too long". +ifdef KBUILD_MODULES +modpost-args += -T modules.order +modpost-deps += modules.order +endif + +ifeq ($(KBUILD_EXTMOD),) + +# Generate the list of in-tree objects in vmlinux +# --------------------------------------------------------------------------- + +# This is used to retrieve symbol versions generated by genksyms. +ifdef CONFIG_MODVERSIONS +vmlinux.symvers Module.symvers: .vmlinux.objs +endif + +# Ignore libgcc.a +# Some architectures do '$(CC) --print-libgcc-file-name' to borrow libgcc.a +# from the toolchain, but there is no EXPORT_SYMBOL in it. + +quiet_cmd_vmlinux_objs = GEN $@ + cmd_vmlinux_objs = \ + for f in $(real-prereqs); do \ + case $${f} in \ + *libgcc.a) ;; \ + *) $(AR) t $${f} ;; \ + esac \ + done > $@ + +targets += .vmlinux.objs +.vmlinux.objs: vmlinux.a $(KBUILD_VMLINUX_LIBS) FORCE + $(call if_changed,vmlinux_objs) + +ifdef CONFIG_TRIM_UNUSED_KSYMS +ksym-wl := $(CONFIG_UNUSED_KSYMS_WHITELIST) +ksym-wl := $(if $(filter-out /%, $(ksym-wl)),$(if $(wildcard $(ksym-wl)),,$(srctree)/))$(ksym-wl) +modpost-args += -t $(addprefix -u , $(ksym-wl)) +modpost-deps += $(ksym-wl) +endif + +ifeq ($(wildcard vmlinux.o),) +missing-input := vmlinux.o +output-symdump := modules-only.symvers +else +modpost-args += vmlinux.o +modpost-deps += vmlinux.o +output-symdump := $(if $(KBUILD_MODULES), Module.symvers, vmlinux.symvers) +endif + +else + +# set src + obj - they may be used in the modules's Makefile +obj := . +src := $(srcroot) + +# Include the module's Makefile to find KBUILD_EXTRA_SYMBOLS +include $(kbuild-file) + +output-symdump := Module.symvers + +ifeq ($(wildcard $(objtree)/Module.symvers),) +missing-input := $(objtree)/Module.symvers +else +modpost-args += -i $(objtree)/Module.symvers +modpost-deps += $(objtree)/Module.symvers +endif + +modpost-args += -e $(addprefix -i , $(KBUILD_EXTRA_SYMBOLS)) + +endif # ($(KBUILD_EXTMOD),) + +quiet_cmd_modpost = MODPOST $@ + cmd_modpost = \ + $(if $(missing-input), \ + echo >&2 "WARNING: $(missing-input) is missing."; \ + echo >&2 " Modules may not have dependencies or modversions."; \ + echo >&2 " You may get many unresolved symbol errors."; \ + echo >&2 " You can set KBUILD_MODPOST_WARN=1 to turn errors into warning"; \ + echo >&2 " if you want to proceed at your own risk.";) \ + $(MODPOST) $(modpost-args) + +targets += $(output-symdump) +$(output-symdump): $(modpost-deps) FORCE + $(call if_changed,modpost) + +__modpost: $(output-symdump) +PHONY += FORCE +FORCE: + +existing-targets := $(wildcard $(sort $(targets))) + +-include $(foreach f,$(existing-targets),$(dir $(f)).$(notdir $(f)).cmd) + +.PHONY: $(PHONY) -- cgit v1.3.1