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 --- arch/mips/bcm63xx/dev-uart.c | 77 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 77 insertions(+) create mode 100644 arch/mips/bcm63xx/dev-uart.c (limited to 'arch/mips/bcm63xx/dev-uart.c') diff --git a/arch/mips/bcm63xx/dev-uart.c b/arch/mips/bcm63xx/dev-uart.c new file mode 100644 index 000000000..5d6bf0445 --- /dev/null +++ b/arch/mips/bcm63xx/dev-uart.c @@ -0,0 +1,77 @@ +/* + * This file is subject to the terms and conditions of the GNU General Public + * License. See the file "COPYING" in the main directory of this archive + * for more details. + * + * Copyright (C) 2008 Maxime Bizon + */ + +#include +#include +#include +#include +#include + +static struct resource uart0_resources[] = { + { + /* start & end filled at runtime */ + .flags = IORESOURCE_MEM, + }, + { + /* start filled at runtime */ + .flags = IORESOURCE_IRQ, + }, +}; + +static struct resource uart1_resources[] = { + { + /* start & end filled at runtime */ + .flags = IORESOURCE_MEM, + }, + { + /* start filled at runtime */ + .flags = IORESOURCE_IRQ, + }, +}; + +static struct platform_device bcm63xx_uart_devices[] = { + { + .name = "bcm63xx_uart", + .id = 0, + .num_resources = ARRAY_SIZE(uart0_resources), + .resource = uart0_resources, + }, + + { + .name = "bcm63xx_uart", + .id = 1, + .num_resources = ARRAY_SIZE(uart1_resources), + .resource = uart1_resources, + } +}; + +int __init bcm63xx_uart_register(unsigned int id) +{ + if (id >= ARRAY_SIZE(bcm63xx_uart_devices)) + return -ENODEV; + + if (id == 1 && (!BCMCPU_IS_3368() && !BCMCPU_IS_6358() && + !BCMCPU_IS_6368())) + return -ENODEV; + + if (id == 0) { + uart0_resources[0].start = bcm63xx_regset_address(RSET_UART0); + uart0_resources[0].end = uart0_resources[0].start + + RSET_UART_SIZE - 1; + uart0_resources[1].start = bcm63xx_get_irq_number(IRQ_UART0); + } + + if (id == 1) { + uart1_resources[0].start = bcm63xx_regset_address(RSET_UART1); + uart1_resources[0].end = uart1_resources[0].start + + RSET_UART_SIZE - 1; + uart1_resources[1].start = bcm63xx_get_irq_number(IRQ_UART1); + } + + return platform_device_register(&bcm63xx_uart_devices[id]); +} -- cgit v1.3.1