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 --- sound/firewire/packets-buffer.c | 77 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 77 insertions(+) create mode 100644 sound/firewire/packets-buffer.c (limited to 'sound/firewire/packets-buffer.c') diff --git a/sound/firewire/packets-buffer.c b/sound/firewire/packets-buffer.c new file mode 100644 index 000000000..2093a5fbd --- /dev/null +++ b/sound/firewire/packets-buffer.c @@ -0,0 +1,77 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * helpers for managing a buffer for many packets + * + * Copyright (c) Clemens Ladisch + */ + +#include +#include +#include +#include "packets-buffer.h" + +/** + * iso_packets_buffer_init - allocates the memory for packets + * @b: the buffer structure to initialize + * @unit: the device at the other end of the stream + * @count: the number of packets + * @packet_size: the (maximum) size of a packet, in bytes + * @direction: %DMA_TO_DEVICE or %DMA_FROM_DEVICE + */ +int iso_packets_buffer_init(struct iso_packets_buffer *b, struct fw_unit *unit, + unsigned int count, unsigned int packet_size, + enum dma_data_direction direction) +{ + unsigned int packets_per_page, pages; + unsigned int i, page_index, offset_in_page; + void *p; + int err; + + b->packets = kmalloc_objs(*b->packets, count); + if (!b->packets) { + err = -ENOMEM; + goto error; + } + + packet_size = L1_CACHE_ALIGN(packet_size); + packets_per_page = PAGE_SIZE / packet_size; + if (WARN_ON(!packets_per_page)) { + err = -EINVAL; + goto err_packets; + } + pages = DIV_ROUND_UP(count, packets_per_page); + + err = fw_iso_buffer_init(&b->iso_buffer, fw_parent_device(unit)->card, + pages, direction); + if (err < 0) + goto err_packets; + + for (i = 0; i < count; ++i) { + page_index = i / packets_per_page; + p = page_address(b->iso_buffer.pages[page_index]); + offset_in_page = (i % packets_per_page) * packet_size; + b->packets[i].buffer = p + offset_in_page; + b->packets[i].offset = page_index * PAGE_SIZE + offset_in_page; + } + + return 0; + +err_packets: + kfree(b->packets); +error: + return err; +} +EXPORT_SYMBOL(iso_packets_buffer_init); + +/** + * iso_packets_buffer_destroy - frees packet buffer resources + * @b: the buffer structure to free + * @unit: the device at the other end of the stream + */ +void iso_packets_buffer_destroy(struct iso_packets_buffer *b, + struct fw_unit *unit) +{ + fw_iso_buffer_destroy(&b->iso_buffer, fw_parent_device(unit)->card); + kfree(b->packets); +} +EXPORT_SYMBOL(iso_packets_buffer_destroy); -- cgit v1.3.1