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/clk/sprd/div.h | 85 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 85 insertions(+) create mode 100644 drivers/clk/sprd/div.h (limited to 'drivers/clk/sprd/div.h') diff --git a/drivers/clk/sprd/div.h b/drivers/clk/sprd/div.h new file mode 100644 index 000000000..a0bcad804 --- /dev/null +++ b/drivers/clk/sprd/div.h @@ -0,0 +1,85 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +// +// Spreadtrum divider clock driver +// +// Copyright (C) 2017 Spreadtrum, Inc. +// Author: Chunyan Zhang + +#ifndef _SPRD_DIV_H_ +#define _SPRD_DIV_H_ + +#include "common.h" + +/** + * struct sprd_div_internal - Internal divider description + * @shift: Bit offset of the divider in its register + * @width: Width of the divider field in its register + * + * That structure represents a single divider, and is meant to be + * embedded in other structures representing the various clock + * classes. + */ +struct sprd_div_internal { + s32 offset; + u8 shift; + u8 width; +}; + +#define _SPRD_DIV_CLK(_offset, _shift, _width) \ + { \ + .offset = _offset, \ + .shift = _shift, \ + .width = _width, \ + } + +struct sprd_div { + struct sprd_div_internal div; + struct sprd_clk_common common; +}; + +#define SPRD_DIV_CLK_HW_INIT_FN(_struct, _name, _parent, _reg, _offset, \ + _shift, _width, _flags, _fn) \ + struct sprd_div _struct = { \ + .div = _SPRD_DIV_CLK(_offset, _shift, _width), \ + .common = { \ + .regmap = NULL, \ + .reg = _reg, \ + .hw.init = _fn(_name, _parent, \ + &sprd_div_ops, _flags), \ + } \ + } + +#define SPRD_DIV_CLK(_struct, _name, _parent, _reg, \ + _shift, _width, _flags) \ + SPRD_DIV_CLK_HW_INIT_FN(_struct, _name, _parent, _reg, 0x0, \ + _shift, _width, _flags, CLK_HW_INIT) + +#define SPRD_DIV_CLK_FW_NAME(_struct, _name, _parent, _reg, \ + _shift, _width, _flags) \ + SPRD_DIV_CLK_HW_INIT_FN(_struct, _name, _parent, _reg, 0x0, \ + _shift, _width, _flags, CLK_HW_INIT_FW_NAME) + +#define SPRD_DIV_CLK_HW(_struct, _name, _parent, _reg, \ + _shift, _width, _flags) \ + SPRD_DIV_CLK_HW_INIT_FN(_struct, _name, _parent, _reg, 0x0, \ + _shift, _width, _flags, CLK_HW_INIT_HW) + +static inline struct sprd_div *hw_to_sprd_div(const struct clk_hw *hw) +{ + struct sprd_clk_common *common = hw_to_sprd_clk_common(hw); + + return container_of(common, struct sprd_div, common); +} + +unsigned long sprd_div_helper_recalc_rate(struct sprd_clk_common *common, + const struct sprd_div_internal *div, + unsigned long parent_rate); + +int sprd_div_helper_set_rate(const struct sprd_clk_common *common, + const struct sprd_div_internal *div, + unsigned long rate, + unsigned long parent_rate); + +extern const struct clk_ops sprd_div_ops; + +#endif /* _SPRD_DIV_H_ */ -- cgit v1.3.1