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/dio/dio-sysfs.c | 82 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 82 insertions(+) create mode 100644 drivers/dio/dio-sysfs.c (limited to 'drivers/dio/dio-sysfs.c') diff --git a/drivers/dio/dio-sysfs.c b/drivers/dio/dio-sysfs.c new file mode 100644 index 000000000..ee1a3b59b --- /dev/null +++ b/drivers/dio/dio-sysfs.c @@ -0,0 +1,82 @@ +/* + * File Attributes for DIO Devices + * + * Copyright (C) 2004 Jochen Friedrich + * + * Loosely based on drivers/pci/pci-sysfs.c and drivers/zorro/zorro-sysfs.c + * + * This file is subject to the terms and conditions of the GNU General Public + * License. See the file COPYING in the main directory of this archive + * for more details. + */ + + +#include +#include +#include + +/* show configuration fields */ + +static ssize_t dio_show_id(struct device *dev, struct device_attribute *attr, char *buf) +{ + struct dio_dev *d; + + d = to_dio_dev(dev); + return sprintf(buf, "0x%02x\n", (d->id & 0xff)); +} +static DEVICE_ATTR(id, S_IRUGO, dio_show_id, NULL); + +static ssize_t dio_show_ipl(struct device *dev, struct device_attribute *attr, char *buf) +{ + struct dio_dev *d; + + d = to_dio_dev(dev); + return sprintf(buf, "0x%02x\n", d->ipl); +} +static DEVICE_ATTR(ipl, S_IRUGO, dio_show_ipl, NULL); + +static ssize_t dio_show_secid(struct device *dev, struct device_attribute *attr, char *buf) +{ + struct dio_dev *d; + + d = to_dio_dev(dev); + return sprintf(buf, "0x%02x\n", ((d->id >> 8)& 0xff)); +} +static DEVICE_ATTR(secid, S_IRUGO, dio_show_secid, NULL); + +static ssize_t dio_show_name(struct device *dev, struct device_attribute *attr, char *buf) +{ + struct dio_dev *d; + + d = to_dio_dev(dev); + return sprintf(buf, "%s\n", d->name); +} +static DEVICE_ATTR(name, S_IRUGO, dio_show_name, NULL); + +static ssize_t dio_show_resource(struct device *dev, struct device_attribute *attr, char *buf) +{ + struct dio_dev *d = to_dio_dev(dev); + + return sprintf(buf, "0x%08lx 0x%08lx 0x%08lx\n", + (unsigned long)dio_resource_start(d), + (unsigned long)dio_resource_end(d), + dio_resource_flags(d)); +} +static DEVICE_ATTR(resource, S_IRUGO, dio_show_resource, NULL); + +int dio_create_sysfs_dev_files(struct dio_dev *d) +{ + struct device *dev = &d->dev; + int error; + + /* current configuration's attributes */ + if ((error = device_create_file(dev, &dev_attr_id)) || + (error = device_create_file(dev, &dev_attr_ipl)) || + (error = device_create_file(dev, &dev_attr_secid)) || + (error = device_create_file(dev, &dev_attr_name)) || + (error = device_create_file(dev, &dev_attr_resource))) + return error; + + return 0; +} + -- cgit v1.3.1