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.c | 80 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 80 insertions(+) create mode 100644 drivers/clk/sprd/div.c (limited to 'drivers/clk/sprd/div.c') diff --git a/drivers/clk/sprd/div.c b/drivers/clk/sprd/div.c new file mode 100644 index 000000000..cd57163a7 --- /dev/null +++ b/drivers/clk/sprd/div.c @@ -0,0 +1,80 @@ +// SPDX-License-Identifier: GPL-2.0 +// +// Spreadtrum divider clock driver +// +// Copyright (C) 2017 Spreadtrum, Inc. +// Author: Chunyan Zhang + +#include + +#include "div.h" + +static int sprd_div_determine_rate(struct clk_hw *hw, + struct clk_rate_request *req) +{ + struct sprd_div *cd = hw_to_sprd_div(hw); + + return divider_determine_rate(&cd->common.hw, req, NULL, cd->div.width, 0); +} + +unsigned long sprd_div_helper_recalc_rate(struct sprd_clk_common *common, + const struct sprd_div_internal *div, + unsigned long parent_rate) +{ + unsigned long val; + unsigned int reg; + + regmap_read(common->regmap, common->reg + div->offset, ®); + val = reg >> div->shift; + val &= (1 << div->width) - 1; + + return divider_recalc_rate(&common->hw, parent_rate, val, NULL, 0, + div->width); +} +EXPORT_SYMBOL_GPL(sprd_div_helper_recalc_rate); + +static unsigned long sprd_div_recalc_rate(struct clk_hw *hw, + unsigned long parent_rate) +{ + struct sprd_div *cd = hw_to_sprd_div(hw); + + return sprd_div_helper_recalc_rate(&cd->common, &cd->div, 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) +{ + unsigned long val; + unsigned int reg; + + val = divider_get_val(rate, parent_rate, NULL, + div->width, 0); + + regmap_read(common->regmap, common->reg + div->offset, ®); + reg &= ~GENMASK(div->width + div->shift - 1, div->shift); + + regmap_write(common->regmap, common->reg + div->offset, + reg | (val << div->shift)); + + return 0; + +} +EXPORT_SYMBOL_GPL(sprd_div_helper_set_rate); + +static int sprd_div_set_rate(struct clk_hw *hw, unsigned long rate, + unsigned long parent_rate) +{ + struct sprd_div *cd = hw_to_sprd_div(hw); + + return sprd_div_helper_set_rate(&cd->common, &cd->div, + rate, parent_rate); +} + +const struct clk_ops sprd_div_ops = { + .recalc_rate = sprd_div_recalc_rate, + .determine_rate = sprd_div_determine_rate, + .set_rate = sprd_div_set_rate, +}; +EXPORT_SYMBOL_GPL(sprd_div_ops); -- cgit v1.3.1