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 --- scripts/kconfig/util.c | 121 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 121 insertions(+) create mode 100644 scripts/kconfig/util.c (limited to 'scripts/kconfig/util.c') diff --git a/scripts/kconfig/util.c b/scripts/kconfig/util.c new file mode 100644 index 000000000..0809aa061 --- /dev/null +++ b/scripts/kconfig/util.c @@ -0,0 +1,121 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2002-2005 Roman Zippel + * Copyright (C) 2002-2005 Sam Ravnborg + */ + +#include +#include +#include + +#include +#include +#include +#include "lkc.h" + +/* hash table of all parsed Kconfig files */ +static HASHTABLE_DEFINE(file_hashtable, 1U << 11); + +struct file { + struct hlist_node node; + struct { + const char *name; + int lineno; + } parent; + char name[]; +}; + +static void die_duplicated_include(struct file *file, + const char *parent, int lineno) +{ + fprintf(stderr, + "%s:%d: error: repeated inclusion of %s\n" + "%s:%d: note: location of first inclusion of %s\n", + parent, lineno, file->name, + file->parent.name, file->parent.lineno, file->name); + exit(1); +} + +/* file already present in list? If not add it */ +const char *file_lookup(const char *name, + const char *parent_name, int parent_lineno) +{ + const char *parent = NULL; + struct file *file; + size_t len; + int hash = hash_str(name); + + if (parent_name) + parent = file_lookup(parent_name, NULL, 0); + + hash_for_each_possible(file_hashtable, file, node, hash) + if (!strcmp(name, file->name)) { + if (!parent_name) + return file->name; + die_duplicated_include(file, parent, parent_lineno); + } + + len = strlen(name); + file = xmalloc(sizeof(*file) + len + 1); + memset(file, 0, sizeof(*file)); + memcpy(file->name, name, len); + file->name[len] = '\0'; + file->parent.name = parent; + file->parent.lineno = parent_lineno; + + hash_add(file_hashtable, &file->node, hash); + + str_printf(&autoconf_cmd, "\t%s \\\n", name); + + return file->name; +} + +/* Allocate initial growable string */ +struct gstr str_new(void) +{ + struct gstr gs; + gs.s = xmalloc(sizeof(char) * 64); + gs.len = 64; + gs.max_width = 0; + strcpy(gs.s, "\0"); + return gs; +} + +/* Free storage for growable string */ +void str_free(struct gstr *gs) +{ + free(gs->s); + gs->s = NULL; + gs->len = 0; +} + +/* Append to growable string */ +void str_append(struct gstr *gs, const char *s) +{ + size_t l; + if (s) { + l = strlen(gs->s) + strlen(s) + 1; + if (l > gs->len) { + gs->s = xrealloc(gs->s, l); + gs->len = l; + } + strcat(gs->s, s); + } +} + +/* Append printf formatted string to growable string */ +void str_printf(struct gstr *gs, const char *fmt, ...) +{ + va_list ap; + char s[10000]; /* big enough... */ + va_start(ap, fmt); + vsnprintf(s, sizeof(s), fmt, ap); + str_append(gs, s); + va_end(ap); +} + +/* Retrieve value of growable string */ +char *str_get(const struct gstr *gs) +{ + return gs->s; +} -- cgit v1.3.1