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/input/keyboard/xtkbd.c | 152 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 152 insertions(+) create mode 100644 drivers/input/keyboard/xtkbd.c (limited to 'drivers/input/keyboard/xtkbd.c') diff --git a/drivers/input/keyboard/xtkbd.c b/drivers/input/keyboard/xtkbd.c new file mode 100644 index 000000000..c0b4978a8 --- /dev/null +++ b/drivers/input/keyboard/xtkbd.c @@ -0,0 +1,152 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Copyright (c) 1999-2001 Vojtech Pavlik + */ + +/* + * XT keyboard driver for Linux + */ + +#include +#include +#include +#include + +#define DRIVER_DESC "XT keyboard driver" + +MODULE_AUTHOR("Vojtech Pavlik "); +MODULE_DESCRIPTION(DRIVER_DESC); +MODULE_LICENSE("GPL"); + +#define XTKBD_EMUL0 0xe0 +#define XTKBD_EMUL1 0xe1 +#define XTKBD_KEY 0x7f +#define XTKBD_RELEASE 0x80 + +static unsigned char xtkbd_keycode[256] = { + 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, + 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, + 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, + 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, + 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, + 80, 81, 82, 83, 0, 0, 0, 87, 88, 0, 0, 0, 0, 0, 0, 0, + 0, 0, 0, 0, 0, 87, 88, 0, 0, 0, 0,110,111,103,108,105, + 106 +}; + +struct xtkbd { + unsigned char keycode[256]; + struct input_dev *dev; + struct serio *serio; + char phys[32]; +}; + +static irqreturn_t xtkbd_interrupt(struct serio *serio, + unsigned char data, unsigned int flags) +{ + struct xtkbd *xtkbd = serio_get_drvdata(serio); + + switch (data) { + case XTKBD_EMUL0: + case XTKBD_EMUL1: + break; + default: + + if (xtkbd->keycode[data & XTKBD_KEY]) { + input_report_key(xtkbd->dev, xtkbd->keycode[data & XTKBD_KEY], !(data & XTKBD_RELEASE)); + input_sync(xtkbd->dev); + } else { + printk(KERN_WARNING "xtkbd.c: Unknown key (scancode %#x) %s.\n", + data & XTKBD_KEY, data & XTKBD_RELEASE ? "released" : "pressed"); + } + } + return IRQ_HANDLED; +} + +static int xtkbd_connect(struct serio *serio, struct serio_driver *drv) +{ + struct xtkbd *xtkbd; + struct input_dev *input_dev; + int err = -ENOMEM; + int i; + + xtkbd = kmalloc_obj(*xtkbd); + input_dev = input_allocate_device(); + if (!xtkbd || !input_dev) + goto fail1; + + xtkbd->serio = serio; + xtkbd->dev = input_dev; + snprintf(xtkbd->phys, sizeof(xtkbd->phys), "%s/input0", serio->phys); + memcpy(xtkbd->keycode, xtkbd_keycode, sizeof(xtkbd->keycode)); + + input_dev->name = "XT Keyboard"; + input_dev->phys = xtkbd->phys; + input_dev->id.bustype = BUS_XTKBD; + input_dev->id.vendor = 0x0001; + input_dev->id.product = 0x0001; + input_dev->id.version = 0x0100; + input_dev->dev.parent = &serio->dev; + + input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_REP); + input_dev->keycode = xtkbd->keycode; + input_dev->keycodesize = sizeof(unsigned char); + input_dev->keycodemax = ARRAY_SIZE(xtkbd_keycode); + + for (i = 0; i < 255; i++) + set_bit(xtkbd->keycode[i], input_dev->keybit); + clear_bit(0, input_dev->keybit); + + serio_set_drvdata(serio, xtkbd); + + err = serio_open(serio, drv); + if (err) + goto fail2; + + err = input_register_device(xtkbd->dev); + if (err) + goto fail3; + + return 0; + + fail3: serio_close(serio); + fail2: serio_set_drvdata(serio, NULL); + fail1: input_free_device(input_dev); + kfree(xtkbd); + return err; +} + +static void xtkbd_disconnect(struct serio *serio) +{ + struct xtkbd *xtkbd = serio_get_drvdata(serio); + + serio_close(serio); + serio_set_drvdata(serio, NULL); + input_unregister_device(xtkbd->dev); + kfree(xtkbd); +} + +static const struct serio_device_id xtkbd_serio_ids[] = { + { + .type = SERIO_XT, + .proto = SERIO_ANY, + .id = SERIO_ANY, + .extra = SERIO_ANY, + }, + { 0 } +}; + +MODULE_DEVICE_TABLE(serio, xtkbd_serio_ids); + +static struct serio_driver xtkbd_drv = { + .driver = { + .name = "xtkbd", + }, + .description = DRIVER_DESC, + .id_table = xtkbd_serio_ids, + .interrupt = xtkbd_interrupt, + .connect = xtkbd_connect, + .disconnect = xtkbd_disconnect, +}; + +module_serio_driver(xtkbd_drv); -- cgit v1.3.1