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 --- include/soc/tegra/flowctrl.h | 71 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 71 insertions(+) create mode 100644 include/soc/tegra/flowctrl.h (limited to 'include/soc/tegra/flowctrl.h') diff --git a/include/soc/tegra/flowctrl.h b/include/soc/tegra/flowctrl.h new file mode 100644 index 000000000..2a60bd493 --- /dev/null +++ b/include/soc/tegra/flowctrl.h @@ -0,0 +1,71 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Functions and macros to control the flowcontroller + * + * Copyright (c) 2010-2012, NVIDIA Corporation. All rights reserved. + */ + +#ifndef __SOC_TEGRA_FLOWCTRL_H__ +#define __SOC_TEGRA_FLOWCTRL_H__ + +#define FLOW_CTRL_HALT_CPU0_EVENTS 0x0 +#define FLOW_CTRL_WAITEVENT (2 << 29) +#define FLOW_CTRL_WAIT_FOR_INTERRUPT (4 << 29) +#define FLOW_CTRL_JTAG_RESUME (1 << 28) +#define FLOW_CTRL_SCLK_RESUME (1 << 27) +#define FLOW_CTRL_HALT_CPU_IRQ (1 << 10) +#define FLOW_CTRL_HALT_CPU_FIQ (1 << 8) +#define FLOW_CTRL_HALT_LIC_IRQ (1 << 11) +#define FLOW_CTRL_HALT_LIC_FIQ (1 << 10) +#define FLOW_CTRL_HALT_GIC_IRQ (1 << 9) +#define FLOW_CTRL_HALT_GIC_FIQ (1 << 8) +#define FLOW_CTRL_CPU0_CSR 0x8 +#define FLOW_CTRL_CSR_INTR_FLAG (1 << 15) +#define FLOW_CTRL_CSR_EVENT_FLAG (1 << 14) +#define FLOW_CTRL_CSR_ENABLE_EXT_CRAIL (1 << 13) +#define FLOW_CTRL_CSR_ENABLE_EXT_NCPU (1 << 12) +#define FLOW_CTRL_CSR_ENABLE_EXT_MASK ( \ + FLOW_CTRL_CSR_ENABLE_EXT_NCPU | \ + FLOW_CTRL_CSR_ENABLE_EXT_CRAIL) +#define FLOW_CTRL_CSR_ENABLE (1 << 0) +#define FLOW_CTRL_HALT_CPU1_EVENTS 0x14 +#define FLOW_CTRL_CPU1_CSR 0x18 + +#define TEGRA20_FLOW_CTRL_CSR_WFE_CPU0 (1 << 4) +#define TEGRA20_FLOW_CTRL_CSR_WFE_BITMAP (3 << 4) +#define TEGRA20_FLOW_CTRL_CSR_WFI_BITMAP 0 + +#define TEGRA30_FLOW_CTRL_CSR_WFI_CPU0 (1 << 8) +#define TEGRA30_FLOW_CTRL_CSR_WFE_BITMAP (0xF << 4) +#define TEGRA30_FLOW_CTRL_CSR_WFI_BITMAP (0xF << 8) + +#ifndef __ASSEMBLER__ +#ifdef CONFIG_SOC_TEGRA_FLOWCTRL +u32 flowctrl_read_cpu_csr(unsigned int cpuid); +void flowctrl_write_cpu_csr(unsigned int cpuid, u32 value); +void flowctrl_write_cpu_halt(unsigned int cpuid, u32 value); + +void flowctrl_cpu_suspend_enter(unsigned int cpuid); +void flowctrl_cpu_suspend_exit(unsigned int cpuid); +#else +static inline u32 flowctrl_read_cpu_csr(unsigned int cpuid) +{ + return 0; +} + +static inline void flowctrl_write_cpu_csr(unsigned int cpuid, u32 value) +{ +} + +static inline void flowctrl_write_cpu_halt(unsigned int cpuid, u32 value) {} + +static inline void flowctrl_cpu_suspend_enter(unsigned int cpuid) +{ +} + +static inline void flowctrl_cpu_suspend_exit(unsigned int cpuid) +{ +} +#endif /* CONFIG_SOC_TEGRA_FLOWCTRL */ +#endif /* __ASSEMBLER__ */ +#endif /* __SOC_TEGRA_FLOWCTRL_H__ */ -- cgit v1.3.1