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/checkversion.pl | 76 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 76 insertions(+) create mode 100755 scripts/checkversion.pl (limited to 'scripts/checkversion.pl') diff --git a/scripts/checkversion.pl b/scripts/checkversion.pl new file mode 100755 index 000000000..94cd49eff --- /dev/null +++ b/scripts/checkversion.pl @@ -0,0 +1,76 @@ +#! /usr/bin/env perl +# SPDX-License-Identifier: GPL-2.0 +# +# checkversion finds uses of all macros in +# where the source files do not #include ; or cases +# of including where it is not needed. +# Copyright (C) 2003, Randy Dunlap + +use strict; + +$| = 1; + +my $debugging; + +foreach my $file (@ARGV) { + next if $file =~ "include/generated/uapi/linux/version\.h"; + next if $file =~ "usr/include/linux/version\.h"; + # Open this file. + open( my $f, '<', $file ) + or die "Can't open $file: $!\n"; + + # Initialize variables. + my ($fInComment, $fInString, $fUseVersion); + my $iLinuxVersion = 0; + + while (<$f>) { + # Strip comments. + $fInComment && (s+^.*?\*/+ +o ? ($fInComment = 0) : next); + m+/\*+o && (s+/\*.*?\*/+ +go, (s+/\*.*$+ +o && ($fInComment = 1))); + + # Pick up definitions. + if ( m/^\s*#/o ) { + $iLinuxVersion = $. if m/^\s*#\s*include\s*"linux\/version\.h"/o; + } + + # Strip strings. + $fInString && (s+^.*?"+ +o ? ($fInString = 0) : next); + m+"+o && (s+".*?"+ +go, (s+".*$+ +o && ($fInString = 1))); + + # Pick up definitions. + if ( m/^\s*#/o ) { + $iLinuxVersion = $. if m/^\s*#\s*include\s*/o; + } + + # Look for uses: LINUX_VERSION_CODE, KERNEL_VERSION, + # LINUX_VERSION_MAJOR, LINUX_VERSION_PATCHLEVEL, LINUX_VERSION_SUBLEVEL + if (($_ =~ /LINUX_VERSION_CODE/) || ($_ =~ /\WKERNEL_VERSION/) || + ($_ =~ /LINUX_VERSION_MAJOR/) || ($_ =~ /LINUX_VERSION_PATCHLEVEL/) || + ($_ =~ /LINUX_VERSION_SUBLEVEL/)) { + $fUseVersion = 1; + last if $iLinuxVersion; + } + } + + # Report used version IDs without include? + if ($fUseVersion && ! $iLinuxVersion) { + print "$file: $.: need linux/version.h\n"; + } + + # Report superfluous includes. + if ($iLinuxVersion && ! $fUseVersion) { + print "$file: $iLinuxVersion linux/version.h not needed.\n"; + } + + # debug: report OK results: + if ($debugging) { + if ($iLinuxVersion && $fUseVersion) { + print "$file: version use is OK ($iLinuxVersion)\n"; + } + if (! $iLinuxVersion && ! $fUseVersion) { + print "$file: version use is OK (none)\n"; + } + } + + close($f); +} -- cgit v1.3.1