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/firmware/imx/sm-cpu.c | 85 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 85 insertions(+) create mode 100644 drivers/firmware/imx/sm-cpu.c (limited to 'drivers/firmware/imx/sm-cpu.c') diff --git a/drivers/firmware/imx/sm-cpu.c b/drivers/firmware/imx/sm-cpu.c new file mode 100644 index 000000000..091b014f7 --- /dev/null +++ b/drivers/firmware/imx/sm-cpu.c @@ -0,0 +1,85 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright 2025 NXP + */ + +#include +#include +#include +#include +#include +#include + +static const struct scmi_imx_cpu_proto_ops *imx_cpu_ops; +static struct scmi_protocol_handle *ph; + +int scmi_imx_cpu_reset_vector_set(u32 cpuid, u64 vector, bool start, bool boot, + bool resume) +{ + if (!ph) + return -EPROBE_DEFER; + + return imx_cpu_ops->cpu_reset_vector_set(ph, cpuid, vector, start, + boot, resume); +} +EXPORT_SYMBOL(scmi_imx_cpu_reset_vector_set); + +int scmi_imx_cpu_start(u32 cpuid, bool start) +{ + if (!ph) + return -EPROBE_DEFER; + + if (start) + return imx_cpu_ops->cpu_start(ph, cpuid, true); + + return imx_cpu_ops->cpu_start(ph, cpuid, false); +}; +EXPORT_SYMBOL(scmi_imx_cpu_start); + +int scmi_imx_cpu_started(u32 cpuid, bool *started) +{ + if (!ph) + return -EPROBE_DEFER; + + if (!started) + return -EINVAL; + + return imx_cpu_ops->cpu_started(ph, cpuid, started); +}; +EXPORT_SYMBOL(scmi_imx_cpu_started); + +static int scmi_imx_cpu_probe(struct scmi_device *sdev) +{ + const struct scmi_handle *handle = sdev->handle; + + if (!handle) + return -ENODEV; + + if (imx_cpu_ops) { + dev_err(&sdev->dev, "sm cpu already initialized\n"); + return -EEXIST; + } + + imx_cpu_ops = handle->devm_protocol_get(sdev, SCMI_PROTOCOL_IMX_CPU, &ph); + if (IS_ERR(imx_cpu_ops)) + return PTR_ERR(imx_cpu_ops); + + return 0; +} + +static const struct scmi_device_id scmi_id_table[] = { + { SCMI_PROTOCOL_IMX_CPU, "imx-cpu" }, + { }, +}; +MODULE_DEVICE_TABLE(scmi, scmi_id_table); + +static struct scmi_driver scmi_imx_cpu_driver = { + .name = "scmi-imx-cpu", + .probe = scmi_imx_cpu_probe, + .id_table = scmi_id_table, +}; +module_scmi_driver(scmi_imx_cpu_driver); + +MODULE_AUTHOR("Peng Fan "); +MODULE_DESCRIPTION("IMX SM CPU driver"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1