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/package/gen-diff-patch | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) create mode 100755 scripts/package/gen-diff-patch (limited to 'scripts/package/gen-diff-patch') diff --git a/scripts/package/gen-diff-patch b/scripts/package/gen-diff-patch new file mode 100755 index 000000000..f272f7770 --- /dev/null +++ b/scripts/package/gen-diff-patch @@ -0,0 +1,38 @@ +#!/bin/sh +# SPDX-License-Identifier: GPL-2.0-only + +set -eu + +diff_patch=$1 + +mkdir -p "$(dirname "${diff_patch}")" + +git -C "${srctree:-.}" diff HEAD > "${diff_patch}" + +if [ ! -s "${diff_patch}" ] || + [ -z "$(git -C "${srctree:-.}" ls-files --other --exclude-standard | head -n1)" ]; then + exit +fi + +# The source tarball, which is generated by 'git archive', contains everything +# you committed in the repository. If you have local diff ('git diff HEAD'), +# it will go into ${diff_patch}. If untracked files are remaining, the resulting +# source package may not be correct. +# +# Examples: +# - You modified a source file to add #include "new-header.h" +# but forgot to add new-header.h +# - You modified a Makefile to add 'obj-$(CONFIG_FOO) += new-dirver.o' +# but you forgot to add new-driver.c +# +# You need to commit them, or at least stage them by 'git add'. +# +# This script does not take care of untracked files because doing so would +# introduce additional complexity. Instead, print a warning message here if +# untracked files are found. +# If all untracked files are just garbage, you can ignore this warning. +echo >&2 "============================ WARNING ============================" +echo >&2 "Your working tree has diff from HEAD, and also untracked file(s)." +echo >&2 "Please make sure you did 'git add' for all new files you need in" +echo >&2 "the source package." +echo >&2 "=================================================================" -- cgit v1.3.1