sched/cache: Keep nr_pref_llc_running in the runnable domain, to fix LLC mis-scheduling buggrafted

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 <zhanxusheng@xiaomi.com>
Suggested-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Kayra Cizmeci <kayracizmeci@gmail.com>
Cc: <stable@kernel.org> # v7.2.x
Link: https://patch.msgid.link/06af61afedac32e6477f57feb4d658f6c411c3af.1790035273.git.tim.c.chen@linux.intel.com

1 files changed, 224 insertions, 0 deletions

diff --git a/scripts/bootgraph.pl b/scripts/bootgraph.pl
new file mode 100755
index 000000000..79c903292
--- /dev/null
+++ b/scripts/bootgraph.pl
@@ -0,0 +1,224 @@
+#!/usr/bin/env perl
+# SPDX-License-Identifier: GPL-2.0-only
+
+# Copyright 2008, Intel Corporation
+#
+# This file is part of the Linux kernel
+#
+# Authors:
+# 	Arjan van de Ven <arjan@linux.intel.com>
+
+
+#
+# This script turns a dmesg output into a SVG graphic that shows which
+# functions take how much time. You can view SVG graphics with various
+# programs, including Inkscape, The Gimp and Firefox.
+#
+#
+# For this script to work, the kernel needs to be compiled with the
+# CONFIG_PRINTK_TIME configuration option enabled, and with
+# "initcall_debug" passed on the kernel command line.
+#
+# usage:
+# 	dmesg | perl scripts/bootgraph.pl > output.svg
+#
+
+use strict;
+use Getopt::Long;
+my $header = 0;
+
+sub help {
+	my $text = << "EOM";
+Usage:
+1) dmesg | perl scripts/bootgraph.pl [OPTION] > output.svg
+2) perl scripts/bootgraph.pl -h
+
+Options:
+	-header	Insert kernel version and date
+EOM
+	my $std=shift;
+	if ($std == 1) {
+		print STDERR $text;
+	} else {
+		print $text;
+	}
+	exit;
+}
+
+GetOptions(
+	'h|help'	=>\&help,
+	'header'	=>\$header
+);
+
+my %start;
+my %end;
+my %type;
+my $done = 0;
+my $maxtime = 0;
+my $firsttime = 99999;
+my $count = 0;
+my %pids;
+my %pidctr;
+
+my $headerstep = 20;
+my $xheader = 15;
+my $yheader = 25;
+my $cyheader = 0;
+
+while (<>) {
+	my $line = $_;
+	if ($line =~ /([0-9\.]+)\] calling  ([a-zA-Z0-9\_\.]+)\+/) {
+		my $func = $2;
+		if ($done == 0) {
+			$start{$func} = $1;
+			$type{$func} = 0;
+			if ($1 < $firsttime) {
+				$firsttime = $1;
+			}
+		}
+		if ($line =~ /\@ ([0-9]+)/) {
+			$pids{$func} = $1;
+		}
+		$count = $count + 1;
+	}
+
+	if ($line =~ /([0-9\.]+)\] async_waiting @ ([0-9]+)/) {
+		my $pid = $2;
+		my $func;
+		if (!defined($pidctr{$pid})) {
+			$func = "wait_" . $pid . "_1";
+			$pidctr{$pid} = 1;
+		} else {
+			$pidctr{$pid} = $pidctr{$pid} + 1;
+			$func = "wait_" . $pid . "_" . $pidctr{$pid};
+		}
+		if ($done == 0) {
+			$start{$func} = $1;
+			$type{$func} = 1;
+			if ($1 < $firsttime) {
+				$firsttime = $1;
+			}
+		}
+		$pids{$func} = $pid;
+		$count = $count + 1;
+	}
+
+	if ($line =~ /([0-9\.]+)\] initcall ([a-zA-Z0-9\_\.]+)\+.*returned/) {
+		if ($done == 0) {
+			$end{$2} = $1;
+			$maxtime = $1;
+		}
+	}
+
+	if ($line =~ /([0-9\.]+)\] async_continuing @ ([0-9]+)/) {
+		my $pid = $2;
+		my $func =  "wait_" . $pid . "_" . $pidctr{$pid};
+		$end{$func} = $1;
+		$maxtime = $1;
+	}
+	if ($line =~ /Write protecting the/) {
+		$done = 1;
+	}
+	if ($line =~ /Freeing unused kernel memory/) {
+		$done = 1;
+	}
+}
+
+if ($count == 0) {
+    print STDERR <<END;
+No data found in the dmesg. Make sure that 'printk.time=1' and
+'initcall_debug' are passed on the kernel command line.
+END
+	help(1);
+    exit 1;
+}
+
+print "<?xml version=\"1.0\" standalone=\"no\"?> \n";
+print "<svg width=\"2000\" height=\"100%\" version=\"1.1\" xmlns=\"http://www.w3.org/2000/svg\">\n";
+
+
+if ($header) {
+	my $version = `uname -a`;
+	my $date = `date`;
+	print "<text transform=\"translate($xheader,$yheader)\">Kernel version: $version</text>\n";
+	$cyheader = $yheader+$headerstep;
+	print "<text transform=\"translate($xheader,$cyheader)\">Date: $date</text>\n";
+}
+
+my @styles;
+
+$styles[0] = "fill:rgb(0,0,255);fill-opacity:0.5;stroke-width:1;stroke:rgb(0,0,0)";
+$styles[1] = "fill:rgb(0,255,0);fill-opacity:0.5;stroke-width:1;stroke:rgb(0,0,0)";
+$styles[2] = "fill:rgb(255,0,20);fill-opacity:0.5;stroke-width:1;stroke:rgb(0,0,0)";
+$styles[3] = "fill:rgb(255,255,20);fill-opacity:0.5;stroke-width:1;stroke:rgb(0,0,0)";
+$styles[4] = "fill:rgb(255,0,255);fill-opacity:0.5;stroke-width:1;stroke:rgb(0,0,0)";
+$styles[5] = "fill:rgb(0,255,255);fill-opacity:0.5;stroke-width:1;stroke:rgb(0,0,0)";
+$styles[6] = "fill:rgb(0,128,255);fill-opacity:0.5;stroke-width:1;stroke:rgb(0,0,0)";
+$styles[7] = "fill:rgb(0,255,128);fill-opacity:0.5;stroke-width:1;stroke:rgb(0,0,0)";
+$styles[8] = "fill:rgb(255,0,128);fill-opacity:0.5;stroke-width:1;stroke:rgb(0,0,0)";
+$styles[9] = "fill:rgb(255,255,128);fill-opacity:0.5;stroke-width:1;stroke:rgb(0,0,0)";
+$styles[10] = "fill:rgb(255,128,255);fill-opacity:0.5;stroke-width:1;stroke:rgb(0,0,0)";
+$styles[11] = "fill:rgb(128,255,255);fill-opacity:0.5;stroke-width:1;stroke:rgb(0,0,0)";
+
+my $style_wait = "fill:rgb(128,128,128);fill-opacity:0.5;stroke-width:0;stroke:rgb(0,0,0)";
+
+my $mult = 1950.0 / ($maxtime - $firsttime);
+my $threshold2 = ($maxtime - $firsttime) / 120.0;
+my $threshold = $threshold2/10;
+my $stylecounter = 0;
+my %rows;
+my $rowscount = 1;
+my @initcalls = sort { $start{$a} <=> $start{$b} } keys(%start);
+
+foreach my $key (@initcalls) {
+	my $duration = $end{$key} - $start{$key};
+
+	if ($duration >= $threshold) {
+		my ($s, $s2, $s3, $e, $w, $y, $y2, $style);
+		my $pid = $pids{$key};
+
+		if (!defined($rows{$pid})) {
+			$rows{$pid} = $rowscount;
+			$rowscount = $rowscount + 1;
+		}
+		$s = ($start{$key} - $firsttime) * $mult;
+		$s2 = $s + 6;
+		$s3 = $s + 1;
+		$e = ($end{$key} - $firsttime) * $mult;
+		$w = $e - $s;
+
+		$y = $rows{$pid} * 150;
+		$y2 = $y + 4;
+
+		$style = $styles[$stylecounter];
+		$stylecounter = $stylecounter + 1;
+		if ($stylecounter > 11) {
+			$stylecounter = 0;
+		};
+
+		if ($type{$key} == 1) {
+			$y = $y + 15;
+			print "<rect x=\"$s\" width=\"$w\" y=\"$y\" height=\"115\" style=\"$style_wait\"/>\n";
+		} else {
+			print "<rect x=\"$s\" width=\"$w\" y=\"$y\" height=\"145\" style=\"$style\"/>\n";
+			if ($duration >= $threshold2) {
+				print "<text transform=\"translate($s2,$y2) rotate(90)\">$key</text>\n";
+			} else {
+				print "<text transform=\"translate($s3,$y2) rotate(90)\" font-size=\"3pt\">$key</text>\n";
+			}
+		}
+	}
+}
+
+
+# print the time line on top
+my $time = $firsttime;
+my $step = ($maxtime - $firsttime) / 15;
+while ($time < $maxtime) {
+	my $s3 = ($time - $firsttime) * $mult;
+	my $tm = int($time * 100) / 100.0;
+	print "<text transform=\"translate($s3,89) rotate(90)\">$tm</text>\n";
+	$time = $time + $step;
+}
+
+print "</svg>\n";