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 --- net/wireless/wext-proc.c | 141 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 141 insertions(+) create mode 100644 net/wireless/wext-proc.c (limited to 'net/wireless/wext-proc.c') diff --git a/net/wireless/wext-proc.c b/net/wireless/wext-proc.c new file mode 100644 index 000000000..be6b2b695 --- /dev/null +++ b/net/wireless/wext-proc.c @@ -0,0 +1,141 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * This file implement the Wireless Extensions proc API. + * + * Authors : Jean Tourrilhes - HPL - + * Copyright (c) 1997-2007 Jean Tourrilhes, All Rights Reserved. + */ + +/* + * The /proc/net/wireless file is a human readable user-space interface + * exporting various wireless specific statistics from the wireless devices. + * This is the most popular part of the Wireless Extensions ;-) + * + * This interface is a pure clone of /proc/net/dev (in net/core/dev.c). + * The content of the file is basically the content of "struct iw_statistics". + */ + +#include +#include +#include +#include +#include +#include +#include +#include + + +static void wireless_seq_printf_stats(struct seq_file *seq, + struct net_device *dev) +{ + /* Get stats from the driver */ + struct iw_statistics *stats = get_wireless_stats(dev); + static struct iw_statistics nullstats = {}; + + /* show device if it's wireless regardless of current stats */ + if (!stats) { +#ifdef CONFIG_WIRELESS_EXT + if (dev->wireless_handlers) + stats = &nullstats; +#endif +#ifdef CONFIG_CFG80211 + if (dev->ieee80211_ptr) + stats = &nullstats; +#endif + } + + if (stats) { + seq_printf(seq, "%6s: %04x %3d%c %3d%c %3d%c %6d %6d %6d " + "%6d %6d %6d\n", + dev->name, stats->status, stats->qual.qual, + stats->qual.updated & IW_QUAL_QUAL_UPDATED + ? '.' : ' ', + ((__s32) stats->qual.level) - + ((stats->qual.updated & IW_QUAL_DBM) ? 0x100 : 0), + stats->qual.updated & IW_QUAL_LEVEL_UPDATED + ? '.' : ' ', + ((__s32) stats->qual.noise) - + ((stats->qual.updated & IW_QUAL_DBM) ? 0x100 : 0), + stats->qual.updated & IW_QUAL_NOISE_UPDATED + ? '.' : ' ', + stats->discard.nwid, stats->discard.code, + stats->discard.fragment, stats->discard.retries, + stats->discard.misc, stats->miss.beacon); + + if (stats != &nullstats) + stats->qual.updated &= ~IW_QUAL_ALL_UPDATED; + } +} + +/* ---------------------------------------------------------------- */ +/* + * Print info for /proc/net/wireless (print all entries) + */ +static int wireless_dev_seq_show(struct seq_file *seq, void *v) +{ + might_sleep(); + + if (v == SEQ_START_TOKEN) + seq_printf(seq, "Inter-| sta-| Quality | Discarded " + "packets | Missed | WE\n" + " face | tus | link level noise | nwid " + "crypt frag retry misc | beacon | %d\n", + WIRELESS_EXT); + else + wireless_seq_printf_stats(seq, v); + return 0; +} + +static void *wireless_dev_seq_start(struct seq_file *seq, loff_t *pos) +{ + struct net *net = seq_file_net(seq); + loff_t off; + struct net_device *dev; + + rtnl_lock(); + if (!*pos) + return SEQ_START_TOKEN; + + off = 1; + for_each_netdev(net, dev) + if (off++ == *pos) + return dev; + return NULL; +} + +static void *wireless_dev_seq_next(struct seq_file *seq, void *v, loff_t *pos) +{ + struct net *net = seq_file_net(seq); + + ++*pos; + + return v == SEQ_START_TOKEN ? + first_net_device(net) : next_net_device(v); +} + +static void wireless_dev_seq_stop(struct seq_file *seq, void *v) +{ + rtnl_unlock(); +} + +static const struct seq_operations wireless_seq_ops = { + .start = wireless_dev_seq_start, + .next = wireless_dev_seq_next, + .stop = wireless_dev_seq_stop, + .show = wireless_dev_seq_show, +}; + +int __net_init wext_proc_init(struct net *net) +{ + /* Create /proc/net/wireless entry */ + if (!proc_create_net("wireless", 0444, net->proc_net, + &wireless_seq_ops, sizeof(struct seq_net_private))) + return -ENOMEM; + + return 0; +} + +void __net_exit wext_proc_exit(struct net *net) +{ + remove_proc_entry("wireless", net->proc_net); +} -- cgit v1.3.1