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 --- tools/testing/shared/shared.mk | 79 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 79 insertions(+) create mode 100644 tools/testing/shared/shared.mk (limited to 'tools/testing/shared/shared.mk') diff --git a/tools/testing/shared/shared.mk b/tools/testing/shared/shared.mk new file mode 100644 index 000000000..5bcdf26c8 --- /dev/null +++ b/tools/testing/shared/shared.mk @@ -0,0 +1,79 @@ +# SPDX-License-Identifier: GPL-2.0 +include ../../scripts/Makefile.arch + +CFLAGS += -I../shared -I. -I../../include -I../../arch/$(SRCARCH)/include \ + -I../../../lib -g -Og -Wall \ + -D_LGPL_SOURCE -fsanitize=address -fsanitize=undefined +CFLAGS += $(EXTRA_CFLAGS) +LDFLAGS += -fsanitize=address -fsanitize=undefined +LDLIBS += -lpthread -lurcu +LIBS := slab.o find_bit.o bitmap.o hweight.o vsprintf.o +SHARED_OFILES = xarray-shared.o radix-tree.o idr.o linux.o $(LIBS) + +SHARED_DEPS = Makefile ../shared/shared.mk ../shared/*.h generated/map-shift.h \ + generated/bit-length.h generated/autoconf.h \ + ../../include/linux/*.h \ + ../../include/asm/*.h \ + ../../arch/$(SRCARCH)/include/asm/*.h \ + ../../../include/linux/xarray.h \ + ../../../include/linux/maple_tree.h \ + ../../../include/linux/radix-tree.h \ + ../../../lib/radix-tree.h \ + ../../../include/linux/idr.h \ + ../../../lib/maple_tree.c \ + ../../../lib/test_maple_tree.c + +ifndef SHIFT + SHIFT=3 +endif + +ifeq ($(BUILD), 32) + CFLAGS += -m32 + LDFLAGS += -m32 +LONG_BIT := 32 +endif + +ifndef LONG_BIT +LONG_BIT := $(shell getconf LONG_BIT) +endif + +%.o: ../shared/%.c + $(CC) -c $(CFLAGS) $< -o $@ + +vpath %.c ../../lib + +$(SHARED_OFILES): $(SHARED_DEPS) + +radix-tree.c: ../../../lib/radix-tree.c + sed -e 's/^static //' -e 's/__always_inline //' -e 's/inline //' < $< > $@ + +idr.c: ../../../lib/idr.c + sed -e 's/^static //' -e 's/__always_inline //' -e 's/inline //' < $< > $@ + +xarray-shared.o: ../shared/xarray-shared.c ../../../lib/xarray.c \ + ../../../lib/test_xarray.c + +maple-shared.o: ../shared/maple-shared.c ../../../lib/maple_tree.c \ + ../../../lib/test_maple_tree.c + +generated/autoconf.h: + @mkdir -p generated + cp ../shared/autoconf.h generated/autoconf.h + +generated/map-shift.h: + @mkdir -p generated + @if ! grep -qws $(SHIFT) generated/map-shift.h; then \ + echo "Generating $@"; \ + echo "#define XA_CHUNK_SHIFT $(SHIFT)" > \ + generated/map-shift.h; \ + fi + +generated/bit-length.h: FORCE + @mkdir -p generated + @if ! grep -qws CONFIG_$(LONG_BIT)BIT generated/bit-length.h; then \ + echo "Generating $@"; \ + echo "#define CONFIG_$(LONG_BIT)BIT 1" > $@; \ + echo "#define CONFIG_PHYS_ADDR_T_$(LONG_BIT)BIT 1" >> $@; \ + fi + +FORCE: ; -- cgit v1.3.1