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 --- drivers/rtc/proc.c | 92 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 92 insertions(+) create mode 100644 drivers/rtc/proc.c (limited to 'drivers/rtc/proc.c') diff --git a/drivers/rtc/proc.c b/drivers/rtc/proc.c new file mode 100644 index 000000000..cbcdbb19d --- /dev/null +++ b/drivers/rtc/proc.c @@ -0,0 +1,92 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * RTC subsystem, proc interface + * + * Copyright (C) 2005-06 Tower Technologies + * Author: Alessandro Zummo + * + * based on arch/arm/common/rtctime.c + */ + +#include +#include +#include +#include + +#include "rtc-core.h" + +#define NAME_SIZE 10 + +#if defined(CONFIG_RTC_HCTOSYS_DEVICE) +static bool is_rtc_hctosys(struct rtc_device *rtc) +{ + int size; + char name[NAME_SIZE]; + + size = snprintf(name, NAME_SIZE, "rtc%d", rtc->id); + if (size >= NAME_SIZE) + return false; + + return !strncmp(name, CONFIG_RTC_HCTOSYS_DEVICE, NAME_SIZE); +} +#else +static bool is_rtc_hctosys(struct rtc_device *rtc) +{ + return (rtc->id == 0); +} +#endif + +static int rtc_proc_show(struct seq_file *seq, void *offset) +{ + int err; + struct rtc_device *rtc = seq->private; + const struct rtc_class_ops *ops = rtc->ops; + struct rtc_wkalrm alrm; + struct rtc_time tm; + + err = rtc_read_time(rtc, &tm); + if (err == 0) { + seq_printf(seq, + "rtc_time\t: %ptRt\n" + "rtc_date\t: %ptRd\n", + &tm, &tm); + } + + err = rtc_read_alarm(rtc, &alrm); + if (err == 0) { + seq_printf(seq, "alrm_time\t: %ptRt\n", &alrm.time); + seq_printf(seq, "alrm_date\t: %ptRd\n", &alrm.time); + seq_printf(seq, "alarm_IRQ\t: %s\n", + alrm.enabled ? "yes" : "no"); + seq_printf(seq, "alrm_pending\t: %s\n", + alrm.pending ? "yes" : "no"); + seq_printf(seq, "update IRQ enabled\t: %s\n", + (rtc->uie_rtctimer.enabled) ? "yes" : "no"); + seq_printf(seq, "periodic IRQ enabled\t: %s\n", + (rtc->pie_enabled) ? "yes" : "no"); + seq_printf(seq, "periodic IRQ frequency\t: %d\n", + rtc->irq_freq); + seq_printf(seq, "max user IRQ frequency\t: %d\n", + rtc->max_user_freq); + } + + seq_printf(seq, "24hr\t\t: yes\n"); + + if (ops->proc) + ops->proc(rtc->dev.parent, seq); + + return 0; +} + +void rtc_proc_add_device(struct rtc_device *rtc) +{ + if (is_rtc_hctosys(rtc)) + proc_create_single_data("driver/rtc", 0, NULL, rtc_proc_show, + rtc); +} + +void rtc_proc_del_device(struct rtc_device *rtc) +{ + if (is_rtc_hctosys(rtc)) + remove_proc_entry("driver/rtc", NULL); +} -- cgit v1.3.1