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.debug | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 52 insertions(+) create mode 100644 scripts/Makefile.debug (limited to 'scripts/Makefile.debug') diff --git a/scripts/Makefile.debug b/scripts/Makefile.debug new file mode 100644 index 000000000..107db997c --- /dev/null +++ b/scripts/Makefile.debug @@ -0,0 +1,52 @@ +DEBUG_CFLAGS := +DEBUG_RUSTFLAGS := + +debug-flags-y := -g + +ifdef CONFIG_DEBUG_INFO_SPLIT +DEBUG_CFLAGS += -gsplit-dwarf +endif + +debug-flags-$(CONFIG_DEBUG_INFO_DWARF4) += -gdwarf-4 +debug-flags-$(CONFIG_DEBUG_INFO_DWARF5) += -gdwarf-5 +ifeq ($(CONFIG_CC_IS_CLANG)$(CONFIG_AS_IS_GNU),yy) +# Clang does not pass -g or -gdwarf-* option down to GAS. +# Add -Wa, prefix to explicitly specify the flags. +KBUILD_AFLAGS += $(addprefix -Wa$(comma), $(debug-flags-y)) +endif +DEBUG_CFLAGS += $(debug-flags-y) +KBUILD_AFLAGS += $(debug-flags-y) + +ifdef CONFIG_DEBUG_INFO_DWARF4 +DEBUG_RUSTFLAGS += -Zdwarf-version=4 +else ifdef CONFIG_DEBUG_INFO_DWARF5 +DEBUG_RUSTFLAGS += -Zdwarf-version=5 +endif + +ifdef CONFIG_DEBUG_INFO_REDUCED +DEBUG_CFLAGS += -fno-var-tracking +DEBUG_RUSTFLAGS += -Cdebuginfo=1 +ifdef CONFIG_CC_IS_GCC +DEBUG_CFLAGS += -femit-struct-debug-baseonly +endif +else +DEBUG_RUSTFLAGS += -Cdebuginfo=2 +endif + +ifdef CONFIG_DEBUG_INFO_COMPRESSED_ZLIB +DEBUG_CFLAGS += -gz=zlib +DEBUG_RUSTFLAGS += -Zdebuginfo-compression=zlib +KBUILD_AFLAGS += -gz=zlib +KBUILD_LDFLAGS += --compress-debug-sections=zlib +else ifdef CONFIG_DEBUG_INFO_COMPRESSED_ZSTD +DEBUG_CFLAGS += -gz=zstd +DEBUG_RUSTFLAGS += -Zdebuginfo-compression=zstd +KBUILD_AFLAGS += -gz=zstd +KBUILD_LDFLAGS += --compress-debug-sections=zstd +endif + +KBUILD_CFLAGS += $(DEBUG_CFLAGS) +export DEBUG_CFLAGS + +KBUILD_RUSTFLAGS += $(DEBUG_RUSTFLAGS) +export DEBUG_RUSTFLAGS -- cgit v1.3.1