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/event.c | 184 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 184 insertions(+) create mode 100644 drivers/acpi/event.c (limited to 'drivers/acpi/event.c') diff --git a/drivers/acpi/event.c b/drivers/acpi/event.c new file mode 100644 index 000000000..4d840d2e7 --- /dev/null +++ b/drivers/acpi/event.c @@ -0,0 +1,184 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * event.c - exporting ACPI events via procfs + * + * Copyright (C) 2001, 2002 Andy Grover + * Copyright (C) 2001, 2002 Paul Diefenbaugh + * + */ + +#define pr_fmt(fmt) "ACPI: " fmt + +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include "internal.h" + +/* ACPI notifier chain */ +static BLOCKING_NOTIFIER_HEAD(acpi_chain_head); + +int acpi_notifier_call_chain(const char *device_class, + const char *bus_id, u32 type, u32 data) +{ + struct acpi_bus_event event; + + strscpy(event.device_class, device_class); + strscpy(event.bus_id, bus_id); + event.type = type; + event.data = data; + return (blocking_notifier_call_chain(&acpi_chain_head, 0, (void *)&event) + == NOTIFY_BAD) ? -EINVAL : 0; +} +EXPORT_SYMBOL(acpi_notifier_call_chain); + +int register_acpi_notifier(struct notifier_block *nb) +{ + return blocking_notifier_chain_register(&acpi_chain_head, nb); +} +EXPORT_SYMBOL(register_acpi_notifier); + +int unregister_acpi_notifier(struct notifier_block *nb) +{ + return blocking_notifier_chain_unregister(&acpi_chain_head, nb); +} +EXPORT_SYMBOL(unregister_acpi_notifier); + +#ifdef CONFIG_NET +static unsigned int acpi_event_seqnum; +struct acpi_genl_event { + acpi_device_class device_class; + char bus_id[15]; + u32 type; + u32 data; +}; + +/* attributes of acpi_genl_family */ +enum { + ACPI_GENL_ATTR_UNSPEC, + ACPI_GENL_ATTR_EVENT, /* ACPI event info needed by user space */ + __ACPI_GENL_ATTR_MAX, +}; +#define ACPI_GENL_ATTR_MAX (__ACPI_GENL_ATTR_MAX - 1) + +/* commands supported by the acpi_genl_family */ +enum { + ACPI_GENL_CMD_UNSPEC, + ACPI_GENL_CMD_EVENT, /* kernel->user notifications for ACPI events */ + __ACPI_GENL_CMD_MAX, +}; +#define ACPI_GENL_CMD_MAX (__ACPI_GENL_CMD_MAX - 1) + +#define ACPI_GENL_FAMILY_NAME "acpi_event" +#define ACPI_GENL_VERSION 0x01 +#define ACPI_GENL_MCAST_GROUP_NAME "acpi_mc_group" + +static const struct genl_multicast_group acpi_event_mcgrps[] = { + { .name = ACPI_GENL_MCAST_GROUP_NAME, }, +}; + +static struct genl_family acpi_event_genl_family __ro_after_init = { + .module = THIS_MODULE, + .name = ACPI_GENL_FAMILY_NAME, + .version = ACPI_GENL_VERSION, + .maxattr = ACPI_GENL_ATTR_MAX, + .mcgrps = acpi_event_mcgrps, + .n_mcgrps = ARRAY_SIZE(acpi_event_mcgrps), +}; + +int acpi_bus_generate_netlink_event(const char *device_class, + const char *bus_id, + u8 type, int data) +{ + struct sk_buff *skb; + struct nlattr *attr; + struct acpi_genl_event *event; + void *msg_header; + int size; + + /* allocate memory */ + size = nla_total_size(sizeof(struct acpi_genl_event)) + + nla_total_size(0); + + skb = genlmsg_new(size, GFP_ATOMIC); + if (!skb) + return -ENOMEM; + + /* add the genetlink message header */ + msg_header = genlmsg_put(skb, 0, acpi_event_seqnum++, + &acpi_event_genl_family, 0, + ACPI_GENL_CMD_EVENT); + if (!msg_header) { + nlmsg_free(skb); + return -ENOMEM; + } + + /* fill the data */ + attr = + nla_reserve(skb, ACPI_GENL_ATTR_EVENT, + sizeof(struct acpi_genl_event)); + if (!attr) { + nlmsg_free(skb); + return -EINVAL; + } + + event = nla_data(attr); + memset(event, 0, sizeof(struct acpi_genl_event)); + + strscpy(event->device_class, device_class, sizeof(event->device_class)); + strscpy(event->bus_id, bus_id, sizeof(event->bus_id)); + event->type = type; + event->data = data; + + /* send multicast genetlink message */ + genlmsg_end(skb, msg_header); + + genlmsg_multicast(&acpi_event_genl_family, skb, 0, 0, GFP_ATOMIC); + return 0; +} + +EXPORT_SYMBOL(acpi_bus_generate_netlink_event); + +static int __init acpi_event_genetlink_init(void) +{ + return genl_register_family(&acpi_event_genl_family); +} + +#else +int acpi_bus_generate_netlink_event(const char *device_class, + const char *bus_id, + u8 type, int data) +{ + return 0; +} + +EXPORT_SYMBOL(acpi_bus_generate_netlink_event); + +static int acpi_event_genetlink_init(void) +{ + return -ENODEV; +} +#endif + +static int __init acpi_event_init(void) +{ + int error; + + if (acpi_disabled) + return 0; + + /* create genetlink for acpi event */ + error = acpi_event_genetlink_init(); + if (error) + pr_warn("Failed to create genetlink family for ACPI event\n"); + + return 0; +} + +fs_initcall(acpi_event_init); -- cgit v1.3.1