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/mksysmap | 94 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 94 insertions(+) create mode 100755 scripts/mksysmap (limited to 'scripts/mksysmap') diff --git a/scripts/mksysmap b/scripts/mksysmap new file mode 100755 index 000000000..856b26ba2 --- /dev/null +++ b/scripts/mksysmap @@ -0,0 +1,94 @@ +#!/bin/sed -f +# SPDX-License-Identifier: GPL-2.0-only +# +# sed script to filter out symbols that are not needed for System.map, +# or not suitable for kallsyms. The input should be 'nm -n '. +# +# System.map is used by module-init tools and some debugging +# tools to retrieve the actual addresses of symbols in the kernel. +# +# readprofile starts reading symbols when _stext is found, and +# continue until it finds a symbol which is not either of 'T', 't', +# 'W' or 'w'. +# +# --------------------------------------------------------------------------- +# Ignored symbol types +# + +# a: local absolute symbols +# N: debugging symbols +# U: undefined global symbols +# w: local weak symbols +/ [aNUw] /d + +# --------------------------------------------------------------------------- +# Ignored prefixes +# (do not forget a space before each pattern) + +# local symbols for ARM, MIPS, etc. +/ \$/d + +# local labels, .LBB, .Ltmpxxx, .L__unnamed_xx, .LASANPC, etc. +/ \.L/d + +# arm64 EFI stub namespace +/ __efistub_/d + +# arm64 local symbols in PIE namespace +/ __pi_\$/d +/ __pi_\.L/d + +# arm64 local symbols in non-VHE KVM namespace +/ __kvm_nvhe_\$/d +/ __kvm_nvhe_\.L/d + +# lld arm/aarch64/mips thunks +/ __[[:alnum:]]*Thunk_/d + +# CFI type identifiers +/ __kcfi_typeid_/d +/ __kvm_nvhe___kcfi_typeid_/d +/ __pi___kcfi_typeid_/d + +# CRC from modversions +/ __crc_/d + +# EXPORT_SYMBOL (symbol name) +/ __kstrtab_/d + +# EXPORT_SYMBOL (namespace) +/ __kstrtabns_/d + +# MODULE_DEVICE_TABLE (symbol name) +/ __mod_device_table__/d + +# --------------------------------------------------------------------------- +# Ignored suffixes +# (do not forget '$' after each pattern) + +# arm +/_from_arm$/d +/_from_thumb$/d +/_veneer$/d + +# --------------------------------------------------------------------------- +# Ignored symbols (exact match) +# (do not forget a space before and '$' after each pattern) + +# for LoongArch? +/ L0$/d + +# ppc +/ _SDA_BASE_$/d +/ _SDA2_BASE_$/d + +# MODULE_INFO() +/ __UNIQUE_ID_modinfo_[0-9]*$/d + +# --------------------------------------------------------------------------- +# Ignored patterns +# (symbols that contain the pattern are ignored) + +# ppc stub +/\.long_branch\./d +/\.plt_branch\./d -- cgit v1.3.1