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.vdsoinst | 45 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 45 insertions(+) create mode 100644 scripts/Makefile.vdsoinst (limited to 'scripts/Makefile.vdsoinst') diff --git a/scripts/Makefile.vdsoinst b/scripts/Makefile.vdsoinst new file mode 100644 index 000000000..d9f724321 --- /dev/null +++ b/scripts/Makefile.vdsoinst @@ -0,0 +1,45 @@ +# SPDX-License-Identifier: GPL-2.0-only +# ========================================================================== +# Install unstripped copies of vDSO +# ========================================================================== + +PHONY := __default +__default: + @: + +include $(srctree)/scripts/Kbuild.include + +install-dir := $(MODLIB)/vdso + +define gen_install_rules + +dest := $(install-dir)/$$(patsubst %.dbg,%,$$(notdir $(1))) + +__default: $$(dest) +$$(dest): $(1) FORCE + $$(call cmd,install) + +build-id-file := $$(shell $(READELF) -n $(1) 2>/dev/null | sed -n 's@^.*Build ID: \(..\)\(.*\)@\1/\2@p') + +ifneq ($$(build-id-file),) +link := $(install-dir)/.build-id/$$(build-id-file).debug + +__default: $$(link) +$$(link): $$(dest) FORCE + $$(call cmd,symlink) +endif + +endef + +$(foreach x, $(sort $(INSTALL_FILES)), $(eval $(call gen_install_rules,$(x)))) + +quiet_cmd_install = INSTALL $@ + cmd_install = mkdir -p $(dir $@); cp $< $@ + +quiet_cmd_symlink = SYMLINK $@ + cmd_symlink = mkdir -p $(dir $@); ln -sf --relative $< $@ + +PHONY += FORCE +FORCE: + +.PHONY: $(PHONY) -- cgit v1.3.1