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/serio/q40kbd.c | 166 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 166 insertions(+) create mode 100644 drivers/input/serio/q40kbd.c (limited to 'drivers/input/serio/q40kbd.c') diff --git a/drivers/input/serio/q40kbd.c b/drivers/input/serio/q40kbd.c new file mode 100644 index 000000000..2f553efbe --- /dev/null +++ b/drivers/input/serio/q40kbd.c @@ -0,0 +1,166 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Copyright (c) 2000-2001 Vojtech Pavlik + * + * Based on the work of: + * Richard Zidlicky + */ + +/* + * Q40 PS/2 keyboard controller driver for Linux/m68k + */ + +#include +#include +#include +#include +#include +#include +#include + +#include +#include +#include +#include +#include + +#define DRV_NAME "q40kbd" + +MODULE_AUTHOR("Vojtech Pavlik "); +MODULE_DESCRIPTION("Q40 PS/2 keyboard controller driver"); +MODULE_LICENSE("GPL"); +MODULE_ALIAS("platform:" DRV_NAME); + +struct q40kbd { + struct serio *port; + spinlock_t lock; +}; + +static irqreturn_t q40kbd_interrupt(int irq, void *dev_id) +{ + struct q40kbd *q40kbd = dev_id; + + guard(spinlock_irqsave)(&q40kbd->lock); + + if (Q40_IRQ_KEYB_MASK & master_inb(INTERRUPT_REG)) + serio_interrupt(q40kbd->port, master_inb(KEYCODE_REG), 0); + + master_outb(-1, KEYBOARD_UNLOCK_REG); + + return IRQ_HANDLED; +} + +/* + * q40kbd_flush() flushes all data that may be in the keyboard buffers + */ + +static void q40kbd_flush(struct q40kbd *q40kbd) +{ + int maxread = 100; + + guard(spinlock_irqsave)(&q40kbd->lock); + + while (maxread-- && (Q40_IRQ_KEYB_MASK & master_inb(INTERRUPT_REG))) + master_inb(KEYCODE_REG); +} + +static void q40kbd_stop(void) +{ + master_outb(0, KEY_IRQ_ENABLE_REG); + master_outb(-1, KEYBOARD_UNLOCK_REG); +} + +/* + * q40kbd_open() is called when a port is open by the higher layer. + * It allocates the interrupt and enables in in the chip. + */ + +static int q40kbd_open(struct serio *port) +{ + struct q40kbd *q40kbd = port->port_data; + + q40kbd_flush(q40kbd); + + /* off we go */ + master_outb(-1, KEYBOARD_UNLOCK_REG); + master_outb(1, KEY_IRQ_ENABLE_REG); + + return 0; +} + +static void q40kbd_close(struct serio *port) +{ + struct q40kbd *q40kbd = port->port_data; + + q40kbd_stop(); + q40kbd_flush(q40kbd); +} + +static int q40kbd_probe(struct platform_device *pdev) +{ + struct q40kbd *q40kbd; + struct serio *port; + int error; + + q40kbd = kzalloc_obj(*q40kbd); + port = kzalloc_obj(*port); + if (!q40kbd || !port) { + error = -ENOMEM; + goto err_free_mem; + } + + q40kbd->port = port; + spin_lock_init(&q40kbd->lock); + + port->id.type = SERIO_8042; + port->open = q40kbd_open; + port->close = q40kbd_close; + port->port_data = q40kbd; + port->dev.parent = &pdev->dev; + strscpy(port->name, "Q40 Kbd Port", sizeof(port->name)); + strscpy(port->phys, "Q40", sizeof(port->phys)); + + q40kbd_stop(); + + error = request_irq(Q40_IRQ_KEYBOARD, q40kbd_interrupt, 0, + DRV_NAME, q40kbd); + if (error) { + dev_err(&pdev->dev, "Can't get irq %d.\n", Q40_IRQ_KEYBOARD); + goto err_free_mem; + } + + serio_register_port(q40kbd->port); + + platform_set_drvdata(pdev, q40kbd); + printk(KERN_INFO "serio: Q40 kbd registered\n"); + + return 0; + +err_free_mem: + kfree(port); + kfree(q40kbd); + return error; +} + +static void q40kbd_remove(struct platform_device *pdev) +{ + struct q40kbd *q40kbd = platform_get_drvdata(pdev); + + /* + * q40kbd_close() will be called as part of unregistering + * and will ensure that IRQ is turned off, so it is safe + * to unregister port first and free IRQ later. + */ + serio_unregister_port(q40kbd->port); + free_irq(Q40_IRQ_KEYBOARD, q40kbd); + kfree(q40kbd); +} + +static struct platform_driver q40kbd_driver = { + .driver = { + .name = "q40kbd", + }, + .remove = q40kbd_remove, +}; + +module_platform_driver_probe(q40kbd_driver, q40kbd_probe); -- cgit v1.3.1