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/misc/smpro-misc.c | 144 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 144 insertions(+) create mode 100644 drivers/misc/smpro-misc.c (limited to 'drivers/misc/smpro-misc.c') diff --git a/drivers/misc/smpro-misc.c b/drivers/misc/smpro-misc.c new file mode 100644 index 000000000..2ca5e3bcc --- /dev/null +++ b/drivers/misc/smpro-misc.c @@ -0,0 +1,144 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Ampere Computing SoC's SMpro Misc Driver + * + * Copyright (c) 2022, Ampere Computing LLC + */ +#include +#include +#include + +/* Boot Stage/Progress Registers */ +#define BOOTSTAGE 0xB0 +#define BOOTSTAGE_LO 0xB1 +#define CUR_BOOTSTAGE 0xB2 +#define BOOTSTAGE_HI 0xB3 + +/* SOC State Registers */ +#define SOC_POWER_LIMIT 0xE5 + +struct smpro_misc { + struct regmap *regmap; +}; + +static ssize_t boot_progress_show(struct device *dev, struct device_attribute *da, char *buf) +{ + struct smpro_misc *misc = dev_get_drvdata(dev); + u16 boot_progress[3] = { 0 }; + u32 bootstage; + u8 boot_stage; + u8 cur_stage; + u32 reg_lo; + u32 reg; + int ret; + + /* Read current boot stage */ + ret = regmap_read(misc->regmap, CUR_BOOTSTAGE, ®); + if (ret) + return ret; + + cur_stage = reg & 0xff; + + ret = regmap_read(misc->regmap, BOOTSTAGE, &bootstage); + if (ret) + return ret; + + boot_stage = (bootstage >> 8) & 0xff; + + if (boot_stage > cur_stage) + return -EINVAL; + + ret = regmap_read(misc->regmap, BOOTSTAGE_LO, ®_lo); + if (!ret) + ret = regmap_read(misc->regmap, BOOTSTAGE_HI, ®); + if (ret) + return ret; + + /* Firmware to report new boot stage next time */ + if (boot_stage < cur_stage) { + ret = regmap_write(misc->regmap, BOOTSTAGE, ((bootstage & 0xff00) | 0x1)); + if (ret) + return ret; + } + + boot_progress[0] = bootstage; + boot_progress[1] = swab16(reg); + boot_progress[2] = swab16(reg_lo); + + return sysfs_emit(buf, "%*phN\n", (int)sizeof(boot_progress), boot_progress); +} + +static DEVICE_ATTR_RO(boot_progress); + +static ssize_t soc_power_limit_show(struct device *dev, struct device_attribute *da, char *buf) +{ + struct smpro_misc *misc = dev_get_drvdata(dev); + unsigned int value; + int ret; + + ret = regmap_read(misc->regmap, SOC_POWER_LIMIT, &value); + if (ret) + return ret; + + return sysfs_emit(buf, "%d\n", value); +} + +static ssize_t soc_power_limit_store(struct device *dev, struct device_attribute *da, + const char *buf, size_t count) +{ + struct smpro_misc *misc = dev_get_drvdata(dev); + unsigned long val; + s32 ret; + + ret = kstrtoul(buf, 0, &val); + if (ret) + return ret; + + ret = regmap_write(misc->regmap, SOC_POWER_LIMIT, (unsigned int)val); + if (ret) + return -EPROTO; + + return count; +} + +static DEVICE_ATTR_RW(soc_power_limit); + +static struct attribute *smpro_misc_attrs[] = { + &dev_attr_boot_progress.attr, + &dev_attr_soc_power_limit.attr, + NULL +}; + +ATTRIBUTE_GROUPS(smpro_misc); + +static int smpro_misc_probe(struct platform_device *pdev) +{ + struct smpro_misc *misc; + + misc = devm_kzalloc(&pdev->dev, sizeof(struct smpro_misc), GFP_KERNEL); + if (!misc) + return -ENOMEM; + + platform_set_drvdata(pdev, misc); + + misc->regmap = dev_get_regmap(pdev->dev.parent, NULL); + if (!misc->regmap) + return -ENODEV; + + return 0; +} + +static struct platform_driver smpro_misc_driver = { + .probe = smpro_misc_probe, + .driver = { + .name = "smpro-misc", + .dev_groups = smpro_misc_groups, + }, +}; + +module_platform_driver(smpro_misc_driver); + +MODULE_AUTHOR("Tung Nguyen "); +MODULE_AUTHOR("Quan Nguyen "); +MODULE_DESCRIPTION("Ampere Altra SMpro Misc driver"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1