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/gate.c | 135 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 135 insertions(+) create mode 100644 drivers/clk/sprd/gate.c (limited to 'drivers/clk/sprd/gate.c') diff --git a/drivers/clk/sprd/gate.c b/drivers/clk/sprd/gate.c new file mode 100644 index 000000000..56e1714b5 --- /dev/null +++ b/drivers/clk/sprd/gate.c @@ -0,0 +1,135 @@ +// SPDX-License-Identifier: GPL-2.0 +// +// Spreadtrum gate clock driver +// +// Copyright (C) 2017 Spreadtrum, Inc. +// Author: Chunyan Zhang + +#include +#include + +#include "gate.h" + +static void clk_gate_toggle(const struct sprd_gate *sg, bool en) +{ + const struct sprd_clk_common *common = &sg->common; + unsigned int reg; + bool set = sg->flags & CLK_GATE_SET_TO_DISABLE ? true : false; + + set ^= en; + + regmap_read(common->regmap, common->reg, ®); + + if (set) + reg |= sg->enable_mask; + else + reg &= ~sg->enable_mask; + + regmap_write(common->regmap, common->reg, reg); +} + +static void clk_sc_gate_toggle(const struct sprd_gate *sg, bool en) +{ + const struct sprd_clk_common *common = &sg->common; + bool set = sg->flags & CLK_GATE_SET_TO_DISABLE ? 1 : 0; + unsigned int offset; + + set ^= en; + + /* + * Each set/clear gate clock has three registers: + * common->reg - base register + * common->reg + offset - set register + * common->reg + 2 * offset - clear register + */ + offset = set ? sg->sc_offset : sg->sc_offset * 2; + + regmap_write(common->regmap, common->reg + offset, + sg->enable_mask); +} + +static void sprd_gate_disable(struct clk_hw *hw) +{ + struct sprd_gate *sg = hw_to_sprd_gate(hw); + + clk_gate_toggle(sg, false); +} + +static int sprd_gate_enable(struct clk_hw *hw) +{ + struct sprd_gate *sg = hw_to_sprd_gate(hw); + + clk_gate_toggle(sg, true); + + return 0; +} + +static void sprd_sc_gate_disable(struct clk_hw *hw) +{ + struct sprd_gate *sg = hw_to_sprd_gate(hw); + + clk_sc_gate_toggle(sg, false); +} + +static int sprd_sc_gate_enable(struct clk_hw *hw) +{ + struct sprd_gate *sg = hw_to_sprd_gate(hw); + + clk_sc_gate_toggle(sg, true); + + return 0; +} + +static int sprd_pll_sc_gate_prepare(struct clk_hw *hw) +{ + struct sprd_gate *sg = hw_to_sprd_gate(hw); + + clk_sc_gate_toggle(sg, true); + udelay(sg->udelay); + + return 0; +} + +static int sprd_gate_is_enabled(struct clk_hw *hw) +{ + struct sprd_gate *sg = hw_to_sprd_gate(hw); + struct sprd_clk_common *common = &sg->common; + struct clk_hw *parent; + unsigned int reg; + + if (sg->flags & SPRD_GATE_NON_AON) { + parent = clk_hw_get_parent(hw); + if (!parent || !clk_hw_is_enabled(parent)) + return 0; + } + + regmap_read(common->regmap, common->reg, ®); + + if (sg->flags & CLK_GATE_SET_TO_DISABLE) + reg ^= sg->enable_mask; + + reg &= sg->enable_mask; + + return reg ? 1 : 0; +} + +const struct clk_ops sprd_gate_ops = { + .disable = sprd_gate_disable, + .enable = sprd_gate_enable, + .is_enabled = sprd_gate_is_enabled, +}; +EXPORT_SYMBOL_GPL(sprd_gate_ops); + +const struct clk_ops sprd_sc_gate_ops = { + .disable = sprd_sc_gate_disable, + .enable = sprd_sc_gate_enable, + .is_enabled = sprd_gate_is_enabled, +}; +EXPORT_SYMBOL_GPL(sprd_sc_gate_ops); + +const struct clk_ops sprd_pll_sc_gate_ops = { + .unprepare = sprd_sc_gate_disable, + .prepare = sprd_pll_sc_gate_prepare, + .is_enabled = sprd_gate_is_enabled, +}; +EXPORT_SYMBOL_GPL(sprd_pll_sc_gate_ops); -- cgit v1.3.1