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/bgrt.c | 94 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 94 insertions(+) create mode 100644 drivers/acpi/bgrt.c (limited to 'drivers/acpi/bgrt.c') diff --git a/drivers/acpi/bgrt.c b/drivers/acpi/bgrt.c new file mode 100644 index 000000000..0fdd581ef --- /dev/null +++ b/drivers/acpi/bgrt.c @@ -0,0 +1,94 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * BGRT boot graphic support + * Authors: Matthew Garrett, Josh Triplett + * Copyright 2012 Red Hat, Inc + * Copyright 2012 Intel Corporation + */ + +#include +#include +#include +#include +#include + +static void *bgrt_image; +static struct kobject *bgrt_kobj; + +#define BGRT_SHOW(_name, _member) \ + static ssize_t _name##_show(struct kobject *kobj, \ + struct kobj_attribute *attr, char *buf) \ + { \ + return sysfs_emit(buf, "%d\n", bgrt_tab._member); \ + } \ + static struct kobj_attribute bgrt_attr_##_name = __ATTR_RO(_name) + +BGRT_SHOW(version, version); +BGRT_SHOW(status, status); +BGRT_SHOW(type, image_type); +BGRT_SHOW(xoffset, image_offset_x); +BGRT_SHOW(yoffset, image_offset_y); + +static __ro_after_init BIN_ATTR_SIMPLE_RO(image); + +static struct attribute *bgrt_attributes[] = { + &bgrt_attr_version.attr, + &bgrt_attr_status.attr, + &bgrt_attr_type.attr, + &bgrt_attr_xoffset.attr, + &bgrt_attr_yoffset.attr, + NULL, +}; + +static const struct bin_attribute *const bgrt_bin_attributes[] = { + &bin_attr_image, + NULL, +}; + +static const struct attribute_group bgrt_attribute_group = { + .attrs = bgrt_attributes, + .bin_attrs = bgrt_bin_attributes, +}; + +int __init acpi_parse_bgrt(struct acpi_table_header *table) +{ + efi_bgrt_init(table); + return 0; +} + +static int __init bgrt_init(void) +{ + int ret; + + if (!bgrt_tab.image_address) + return -ENODEV; + + bgrt_image = memremap(bgrt_tab.image_address, bgrt_image_size, + MEMREMAP_WB); + if (!bgrt_image) { + pr_notice("Ignoring BGRT: failed to map image memory\n"); + return -ENOMEM; + } + + bin_attr_image.private = bgrt_image; + bin_attr_image.size = bgrt_image_size; + + bgrt_kobj = kobject_create_and_add("bgrt", acpi_kobj); + if (!bgrt_kobj) { + ret = -EINVAL; + goto out_memmap; + } + + ret = sysfs_create_group(bgrt_kobj, &bgrt_attribute_group); + if (ret) + goto out_kobject; + + return 0; + +out_kobject: + kobject_put(bgrt_kobj); +out_memmap: + memunmap(bgrt_image); + return ret; +} +device_initcall(bgrt_init); -- cgit v1.3.1