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/acpi/proc.c | 143 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 143 insertions(+) create mode 100644 drivers/acpi/proc.c (limited to 'drivers/acpi/proc.c') diff --git a/drivers/acpi/proc.c b/drivers/acpi/proc.c new file mode 100644 index 000000000..c08ead072 --- /dev/null +++ b/drivers/acpi/proc.c @@ -0,0 +1,143 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include +#include +#include + +#include "sleep.h" +#include "internal.h" + +/* + * this file provides support for: + * /proc/acpi/wakeup + */ + +static int +acpi_system_wakeup_device_seq_show(struct seq_file *seq, void *offset) +{ + struct acpi_device *dev, *tmp; + + seq_printf(seq, "Device\tS-state\t Status Sysfs node\n"); + + mutex_lock(&acpi_device_lock); + list_for_each_entry_safe(dev, tmp, &acpi_wakeup_device_list, + wakeup_list) { + struct acpi_device_physical_node *entry; + + if (!dev->wakeup.flags.valid) + continue; + + seq_printf(seq, "%s\t S%llu\t", + dev->pnp.bus_id, + dev->wakeup.sleep_state); + + mutex_lock(&dev->physical_node_lock); + + if (!dev->physical_node_count) { + seq_printf(seq, "%c%-8s\n", + dev->wakeup.flags.valid ? '*' : ' ', + str_enabled_disabled(device_may_wakeup(&dev->dev))); + } else { + struct device *ldev; + list_for_each_entry(entry, &dev->physical_node_list, + node) { + ldev = get_device(entry->dev); + if (!ldev) + continue; + + if (&entry->node != + dev->physical_node_list.next) + seq_printf(seq, "\t\t"); + + seq_printf(seq, "%c%-8s %s:%s\n", + dev->wakeup.flags.valid ? '*' : ' ', + str_enabled_disabled(device_may_wakeup(ldev) || + device_may_wakeup(&dev->dev)), + ldev->bus ? ldev->bus->name : + "no-bus", dev_name(ldev)); + put_device(ldev); + } + } + + mutex_unlock(&dev->physical_node_lock); + } + mutex_unlock(&acpi_device_lock); + return 0; +} + +static void physical_device_enable_wakeup(struct acpi_device *adev) +{ + struct acpi_device_physical_node *entry; + + mutex_lock(&adev->physical_node_lock); + + list_for_each_entry(entry, + &adev->physical_node_list, node) + if (entry->dev && device_can_wakeup(entry->dev)) { + bool enable = !device_may_wakeup(entry->dev); + device_set_wakeup_enable(entry->dev, enable); + } + + mutex_unlock(&adev->physical_node_lock); +} + +static ssize_t +acpi_system_write_wakeup_device(struct file *file, + const char __user * buffer, + size_t count, loff_t * ppos) +{ + struct acpi_device *dev, *tmp; + char strbuf[5]; + char str[5] = ""; + + if (count > 4) + count = 4; + + if (copy_from_user(strbuf, buffer, count)) + return -EFAULT; + strbuf[count] = '\0'; + sscanf(strbuf, "%s", str); + + mutex_lock(&acpi_device_lock); + list_for_each_entry_safe(dev, tmp, &acpi_wakeup_device_list, + wakeup_list) { + if (!dev->wakeup.flags.valid) + continue; + + if (!strncmp(dev->pnp.bus_id, str, 4)) { + if (device_can_wakeup(&dev->dev)) { + bool enable = !device_may_wakeup(&dev->dev); + device_set_wakeup_enable(&dev->dev, enable); + } else { + physical_device_enable_wakeup(dev); + } + break; + } + } + mutex_unlock(&acpi_device_lock); + return count; +} + +static int +acpi_system_wakeup_device_open_fs(struct inode *inode, struct file *file) +{ + return single_open(file, acpi_system_wakeup_device_seq_show, + pde_data(inode)); +} + +static const struct proc_ops acpi_system_wakeup_device_proc_ops = { + .proc_open = acpi_system_wakeup_device_open_fs, + .proc_read = seq_read, + .proc_write = acpi_system_write_wakeup_device, + .proc_lseek = seq_lseek, + .proc_release = single_release, +}; + +void __init acpi_sleep_proc_init(void) +{ + /* 'wakeup device' [R/W] */ + proc_create("wakeup", 0644, acpi_root_dir, &acpi_system_wakeup_device_proc_ops); +} -- cgit v1.3.1