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.clean | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 63 insertions(+) create mode 100644 scripts/Makefile.clean (limited to 'scripts/Makefile.clean') diff --git a/scripts/Makefile.clean b/scripts/Makefile.clean new file mode 100644 index 000000000..6ead00ec7 --- /dev/null +++ b/scripts/Makefile.clean @@ -0,0 +1,63 @@ +# SPDX-License-Identifier: GPL-2.0 +# ========================================================================== +# Cleaning up +# ========================================================================== + +src := $(srcroot)/$(obj) + +PHONY := __clean +__clean: + +include $(srctree)/scripts/Kbuild.include +include $(kbuild-file) + +# Figure out what we need to build from the various variables +# ========================================================================== + +subdir-ymn := $(sort $(subdir-y) $(subdir-m) $(subdir-) \ + $(patsubst %/,%, $(filter %/, $(obj-y) $(obj-m) $(obj-)))) + +# Add subdir path + +subdir-ymn := $(addprefix $(obj)/,$(subdir-ymn)) + +# build a list of files to remove, usually relative to the current +# directory + +__clean-files := \ + $(clean-files) $(targets) $(hostprogs) $(userprogs) \ + $(extra-y) $(extra-m) $(extra-) \ + $(always-y) $(always-m) $(always-) \ + $(hostprogs-always-y) $(hostprogs-always-m) $(hostprogs-always-) \ + $(userprogs-always-y) $(userprogs-always-m) $(userprogs-always-) + +__clean-files := $(filter-out $(no-clean-files), $(__clean-files)) + +__clean-files := $(wildcard $(addprefix $(obj)/, $(__clean-files))) + +# ========================================================================== + +# To make this rule robust against "Argument list too long" error, +# remove $(obj)/ prefix, and restore it by a shell command. +quiet_cmd_clean = CLEAN $(obj) + cmd_clean = printf '$(obj)/%s ' $(patsubst $(obj)/%,%,$(__clean-files)) | xargs rm -rf + +__clean: $(subdir-ymn) +ifneq ($(strip $(__clean-files)),) + $(call cmd,clean) +endif + @: + + +# =========================================================================== +# Generic stuff +# =========================================================================== + +# Descending +# --------------------------------------------------------------------------- + +PHONY += $(subdir-ymn) +$(subdir-ymn): + $(Q)$(MAKE) $(clean)=$@ + +.PHONY: $(PHONY) -- cgit v1.3.1