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/clocksource/timer-xilinx.h | 73 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 73 insertions(+) create mode 100644 include/clocksource/timer-xilinx.h (limited to 'include/clocksource/timer-xilinx.h') diff --git a/include/clocksource/timer-xilinx.h b/include/clocksource/timer-xilinx.h new file mode 100644 index 000000000..d116f18de --- /dev/null +++ b/include/clocksource/timer-xilinx.h @@ -0,0 +1,73 @@ +/* SPDX-License-Identifier: GPL-2.0+ */ +/* + * Copyright (C) 2021 Sean Anderson + */ + +#ifndef XILINX_TIMER_H +#define XILINX_TIMER_H + +#include + +#define TCSR0 0x00 +#define TLR0 0x04 +#define TCR0 0x08 +#define TCSR1 0x10 +#define TLR1 0x14 +#define TCR1 0x18 + +#define TCSR_MDT BIT(0) +#define TCSR_UDT BIT(1) +#define TCSR_GENT BIT(2) +#define TCSR_CAPT BIT(3) +#define TCSR_ARHT BIT(4) +#define TCSR_LOAD BIT(5) +#define TCSR_ENIT BIT(6) +#define TCSR_ENT BIT(7) +#define TCSR_TINT BIT(8) +#define TCSR_PWMA BIT(9) +#define TCSR_ENALL BIT(10) +#define TCSR_CASC BIT(11) + +struct clk; +struct device_node; +struct regmap; + +/** + * struct xilinx_timer_priv - Private data for Xilinx AXI timer drivers + * @map: Regmap of the device, possibly with an offset + * @clk: Parent clock + * @max: Maximum value of the counters + */ +struct xilinx_timer_priv { + struct regmap *map; + struct clk *clk; + u64 max; +}; + +/** + * xilinx_timer_tlr_cycles() - Calculate the TLR for a period specified + * in clock cycles + * @priv: The timer's private data + * @tcsr: The value of the TCSR register for this counter + * @cycles: The number of cycles in this period + * + * Callers of this function MUST ensure that @cycles is representable as + * a TLR. + * + * Return: The calculated value for TLR + */ +u32 xilinx_timer_tlr_cycles(struct xilinx_timer_priv *priv, u32 tcsr, + u64 cycles); + +/** + * xilinx_timer_get_period() - Get the current period of a counter + * @priv: The timer's private data + * @tlr: The value of TLR for this counter + * @tcsr: The value of TCSR for this counter + * + * Return: The period, in ns + */ +unsigned int xilinx_timer_get_period(struct xilinx_timer_priv *priv, + u32 tlr, u32 tcsr); + +#endif /* XILINX_TIMER_H */ -- cgit v1.3.1