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/viperboard.c | 126 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 126 insertions(+) create mode 100644 drivers/mfd/viperboard.c (limited to 'drivers/mfd/viperboard.c') diff --git a/drivers/mfd/viperboard.c b/drivers/mfd/viperboard.c new file mode 100644 index 000000000..36be8e69f --- /dev/null +++ b/drivers/mfd/viperboard.c @@ -0,0 +1,126 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Nano River Technologies viperboard driver + * + * This is the core driver for the viperboard. There are cell drivers + * available for I2C, ADC and both GPIOs. SPI is not yet supported. + * The drivers do not support all features the board exposes. See user + * manual of the viperboard. + * + * (C) 2012 by Lemonage GmbH + * Author: Lars Poeschel + * All rights reserved. + */ + +#include +#include +#include +#include +#include +#include + +#include +#include + +#include + + +static const struct usb_device_id vprbrd_table[] = { + { USB_DEVICE(0x2058, 0x1005) }, /* Nano River Technologies */ + { } /* Terminating entry */ +}; + +MODULE_DEVICE_TABLE(usb, vprbrd_table); + +static const struct mfd_cell vprbrd_devs[] = { + { + .name = "viperboard-gpio", + }, + { + .name = "viperboard-i2c", + }, + { + .name = "viperboard-adc", + }, +}; + +static int vprbrd_probe(struct usb_interface *interface, + const struct usb_device_id *id) +{ + struct vprbrd *vb; + + u16 version = 0; + int pipe, ret; + + /* allocate memory for our device state and initialize it */ + vb = kzalloc_obj(*vb); + if (!vb) + return -ENOMEM; + + mutex_init(&vb->lock); + + vb->usb_dev = interface_to_usbdev(interface); + + /* save our data pointer in this interface device */ + usb_set_intfdata(interface, vb); + dev_set_drvdata(&vb->pdev.dev, vb); + + /* get version information, major first, minor then */ + pipe = usb_rcvctrlpipe(vb->usb_dev, 0); + ret = usb_control_msg(vb->usb_dev, pipe, VPRBRD_USB_REQUEST_MAJOR, + VPRBRD_USB_TYPE_IN, 0x0000, 0x0000, vb->buf, 1, + VPRBRD_USB_TIMEOUT_MS); + if (ret == 1) + version = vb->buf[0]; + + ret = usb_control_msg(vb->usb_dev, pipe, VPRBRD_USB_REQUEST_MINOR, + VPRBRD_USB_TYPE_IN, 0x0000, 0x0000, vb->buf, 1, + VPRBRD_USB_TIMEOUT_MS); + if (ret == 1) { + version <<= 8; + version = version | vb->buf[0]; + } + + dev_info(&interface->dev, + "version %x.%02x found at bus %03d address %03d\n", + version >> 8, version & 0xff, + vb->usb_dev->bus->busnum, vb->usb_dev->devnum); + + ret = mfd_add_hotplug_devices(&interface->dev, vprbrd_devs, + ARRAY_SIZE(vprbrd_devs)); + if (ret != 0) { + dev_err(&interface->dev, "Failed to add mfd devices to core."); + goto error; + } + + return 0; + +error: + kfree(vb); + + return ret; +} + +static void vprbrd_disconnect(struct usb_interface *interface) +{ + struct vprbrd *vb = usb_get_intfdata(interface); + + mfd_remove_devices(&interface->dev); + usb_set_intfdata(interface, NULL); + kfree(vb); + + dev_dbg(&interface->dev, "disconnected\n"); +} + +static struct usb_driver vprbrd_driver = { + .name = "viperboard", + .probe = vprbrd_probe, + .disconnect = vprbrd_disconnect, + .id_table = vprbrd_table, +}; + +module_usb_driver(vprbrd_driver); + +MODULE_DESCRIPTION("Nano River Technologies viperboard mfd core driver"); +MODULE_AUTHOR("Lars Poeschel "); +MODULE_LICENSE("GPL"); -- cgit v1.3.1