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/mfd/ocelot.h | 49 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 49 insertions(+) create mode 100644 drivers/mfd/ocelot.h (limited to 'drivers/mfd/ocelot.h') diff --git a/drivers/mfd/ocelot.h b/drivers/mfd/ocelot.h new file mode 100644 index 000000000..b8bc2f148 --- /dev/null +++ b/drivers/mfd/ocelot.h @@ -0,0 +1,49 @@ +/* SPDX-License-Identifier: GPL-2.0 OR MIT */ +/* Copyright 2021, 2022 Innovative Advantage Inc. */ + +#ifndef _MFD_OCELOT_H +#define _MFD_OCELOT_H + +#include + +struct device; +struct regmap; +struct resource; + +/** + * struct ocelot_ddata - Private data for an external Ocelot chip + * @gcb_regmap: General Configuration Block regmap. Used for + * operations like chip reset. + * @cpuorg_regmap: CPU Device Origin Block regmap. Used for operations + * like SPI bus configuration. + * @spi_padding_bytes: Number of padding bytes that must be thrown out before + * read data gets returned. This is calculated during + * initialization based on bus speed. + * @dummy_buf: Zero-filled buffer of spi_padding_bytes size. The dummy + * bytes that will be sent out between the address and + * data of a SPI read operation. + */ +struct ocelot_ddata { + struct regmap *gcb_regmap; + struct regmap *cpuorg_regmap; + int spi_padding_bytes; + void *dummy_buf; +}; + +int ocelot_chip_reset(struct device *dev); +int ocelot_core_init(struct device *dev); + +/* SPI-specific routines that won't be necessary for other interfaces */ +struct regmap *ocelot_spi_init_regmap(struct device *dev, + const struct resource *res); + +#define OCELOT_SPI_BYTE_ORDER_LE 0x00000000 +#define OCELOT_SPI_BYTE_ORDER_BE 0x81818181 + +#ifdef __LITTLE_ENDIAN +#define OCELOT_SPI_BYTE_ORDER OCELOT_SPI_BYTE_ORDER_LE +#else +#define OCELOT_SPI_BYTE_ORDER OCELOT_SPI_BYTE_ORDER_BE +#endif + +#endif -- cgit v1.3.1