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/synth/util_mem.c | 175 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 175 insertions(+) create mode 100644 sound/synth/util_mem.c (limited to 'sound/synth/util_mem.c') diff --git a/sound/synth/util_mem.c b/sound/synth/util_mem.c new file mode 100644 index 000000000..21893e561 --- /dev/null +++ b/sound/synth/util_mem.c @@ -0,0 +1,175 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Copyright (C) 2000 Takashi Iwai + * + * Generic memory management routines for soundcard memory allocation + */ + +#include +#include +#include +#include +#include +#include + +MODULE_AUTHOR("Takashi Iwai"); +MODULE_DESCRIPTION("Generic memory management routines for soundcard memory allocation"); +MODULE_LICENSE("GPL"); + +#define get_memblk(p) list_entry(p, struct snd_util_memblk, list) + +/* + * create a new memory manager + */ +struct snd_util_memhdr * +snd_util_memhdr_new(int memsize) +{ + struct snd_util_memhdr *hdr; + + hdr = kzalloc_obj(*hdr); + if (hdr == NULL) + return NULL; + hdr->size = memsize; + mutex_init(&hdr->block_mutex); + INIT_LIST_HEAD(&hdr->block); + + return hdr; +} + +/* + * free a memory manager + */ +void snd_util_memhdr_free(struct snd_util_memhdr *hdr) +{ + struct list_head *p; + + if (!hdr) + return; + /* release all blocks */ + while ((p = hdr->block.next) != &hdr->block) { + list_del(p); + kfree(get_memblk(p)); + } + kfree(hdr); +} + +/* + * allocate a memory block (without mutex) + */ +struct snd_util_memblk * +__snd_util_mem_alloc(struct snd_util_memhdr *hdr, int size) +{ + struct snd_util_memblk *blk; + unsigned int units, prev_offset; + struct list_head *p; + + if (snd_BUG_ON(!hdr || size <= 0)) + return NULL; + + /* word alignment */ + units = size; + if (units & 1) + units++; + if (units > hdr->size) + return NULL; + + /* look for empty block */ + prev_offset = 0; + list_for_each(p, &hdr->block) { + blk = get_memblk(p); + if (blk->offset - prev_offset >= units) + goto __found; + prev_offset = blk->offset + blk->size; + } + if (hdr->size - prev_offset < units) + return NULL; + +__found: + return __snd_util_memblk_new(hdr, units, p->prev); +} + + +/* + * create a new memory block with the given size + * the block is linked next to prev + */ +struct snd_util_memblk * +__snd_util_memblk_new(struct snd_util_memhdr *hdr, unsigned int units, + struct list_head *prev) +{ + struct snd_util_memblk *blk; + + blk = kmalloc(sizeof(struct snd_util_memblk) + hdr->block_extra_size, + GFP_KERNEL); + if (blk == NULL) + return NULL; + + if (prev == &hdr->block) + blk->offset = 0; + else { + struct snd_util_memblk *p = get_memblk(prev); + blk->offset = p->offset + p->size; + } + blk->size = units; + list_add(&blk->list, prev); + hdr->nblocks++; + hdr->used += units; + return blk; +} + + +/* + * allocate a memory block (with mutex) + */ +struct snd_util_memblk * +snd_util_mem_alloc(struct snd_util_memhdr *hdr, int size) +{ + guard(mutex)(&hdr->block_mutex); + return __snd_util_mem_alloc(hdr, size); +} + + +/* + * remove the block from linked-list and free resource + * (without mutex) + */ +void +__snd_util_mem_free(struct snd_util_memhdr *hdr, struct snd_util_memblk *blk) +{ + list_del(&blk->list); + hdr->nblocks--; + hdr->used -= blk->size; + kfree(blk); +} + +/* + * free a memory block (with mutex) + */ +int snd_util_mem_free(struct snd_util_memhdr *hdr, struct snd_util_memblk *blk) +{ + if (snd_BUG_ON(!hdr || !blk)) + return -EINVAL; + + guard(mutex)(&hdr->block_mutex); + __snd_util_mem_free(hdr, blk); + return 0; +} + +/* + * return available memory size + */ +int snd_util_mem_avail(struct snd_util_memhdr *hdr) +{ + guard(mutex)(&hdr->block_mutex); + return hdr->size - hdr->used; +} + + +EXPORT_SYMBOL(snd_util_memhdr_new); +EXPORT_SYMBOL(snd_util_memhdr_free); +EXPORT_SYMBOL(snd_util_mem_alloc); +EXPORT_SYMBOL(snd_util_mem_free); +EXPORT_SYMBOL(snd_util_mem_avail); +EXPORT_SYMBOL(__snd_util_mem_alloc); +EXPORT_SYMBOL(__snd_util_mem_free); +EXPORT_SYMBOL(__snd_util_memblk_new); -- cgit v1.3.1