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/soc/gemini/Makefile | 2 ++ drivers/soc/gemini/soc-gemini.c | 71 +++++++++++++++++++++++++++++++++++++++++ 2 files changed, 73 insertions(+) create mode 100644 drivers/soc/gemini/Makefile create mode 100644 drivers/soc/gemini/soc-gemini.c (limited to 'drivers/soc/gemini') diff --git a/drivers/soc/gemini/Makefile b/drivers/soc/gemini/Makefile new file mode 100644 index 000000000..8cbd1e45d --- /dev/null +++ b/drivers/soc/gemini/Makefile @@ -0,0 +1,2 @@ +# SPDX-License-Identifier: GPL-2.0 +obj-y += soc-gemini.o diff --git a/drivers/soc/gemini/soc-gemini.c b/drivers/soc/gemini/soc-gemini.c new file mode 100644 index 000000000..642b96c91 --- /dev/null +++ b/drivers/soc/gemini/soc-gemini.c @@ -0,0 +1,71 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2017 Linaro Ltd. + * + * Author: Linus Walleij + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2, as + * published by the Free Software Foundation. + * + */ +#include +#include +#include +#include +#include + +#define GLOBAL_WORD_ID 0x00 +#define GEMINI_GLOBAL_ARB1_CTRL 0x2c +#define GEMINI_ARB1_BURST_MASK GENMASK(21, 16) +#define GEMINI_ARB1_BURST_SHIFT 16 +/* These all define the priority on the BUS2 backplane */ +#define GEMINI_ARB1_PRIO_MASK GENMASK(9, 0) +#define GEMINI_ARB1_DMAC_HIGH_PRIO BIT(0) +#define GEMINI_ARB1_IDE_HIGH_PRIO BIT(1) +#define GEMINI_ARB1_RAID_HIGH_PRIO BIT(2) +#define GEMINI_ARB1_SECURITY_HIGH_PRIO BIT(3) +#define GEMINI_ARB1_GMAC0_HIGH_PRIO BIT(4) +#define GEMINI_ARB1_GMAC1_HIGH_PRIO BIT(5) +#define GEMINI_ARB1_USB0_HIGH_PRIO BIT(6) +#define GEMINI_ARB1_USB1_HIGH_PRIO BIT(7) +#define GEMINI_ARB1_PCI_HIGH_PRIO BIT(8) +#define GEMINI_ARB1_TVE_HIGH_PRIO BIT(9) + +#define GEMINI_DEFAULT_BURST_SIZE 0x20 +#define GEMINI_DEFAULT_PRIO (GEMINI_ARB1_GMAC0_HIGH_PRIO | \ + GEMINI_ARB1_GMAC1_HIGH_PRIO) + +static int __init gemini_soc_init(void) +{ + struct regmap *map; + u32 rev; + u32 val; + int ret; + + /* Multiplatform guard, only proceed on Gemini */ + if (!of_machine_is_compatible("cortina,gemini")) + return 0; + + map = syscon_regmap_lookup_by_compatible("cortina,gemini-syscon"); + if (IS_ERR(map)) + return PTR_ERR(map); + ret = regmap_read(map, GLOBAL_WORD_ID, &rev); + if (ret) + return ret; + + val = (GEMINI_DEFAULT_BURST_SIZE << GEMINI_ARB1_BURST_SHIFT) | + GEMINI_DEFAULT_PRIO; + + /* Set up system arbitration */ + regmap_update_bits(map, + GEMINI_GLOBAL_ARB1_CTRL, + GEMINI_ARB1_BURST_MASK | GEMINI_ARB1_PRIO_MASK, + val); + + pr_info("Gemini SoC %04x revision %02x, set arbitration %08x\n", + rev >> 8, rev & 0xff, val); + + return 0; +} +subsys_initcall(gemini_soc_init); -- cgit v1.3.1