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/imx/cpu.h | 37 +++++++++++++++++++++++++++++++++++++ 1 file changed, 37 insertions(+) create mode 100644 include/soc/imx/cpu.h (limited to 'include/soc/imx/cpu.h') diff --git a/include/soc/imx/cpu.h b/include/soc/imx/cpu.h new file mode 100644 index 000000000..0bf610aca --- /dev/null +++ b/include/soc/imx/cpu.h @@ -0,0 +1,37 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ + +#ifndef __IMX_CPU_H__ +#define __IMX_CPU_H__ + +#define MXC_CPU_MX1 1 +#define MXC_CPU_MX21 21 +#define MXC_CPU_MX25 25 +#define MXC_CPU_MX27 27 +#define MXC_CPU_MX31 31 +#define MXC_CPU_MX35 35 +#define MXC_CPU_MX50 50 +#define MXC_CPU_MX51 51 +#define MXC_CPU_MX53 53 +#define MXC_CPU_IMX6SL 0x60 +#define MXC_CPU_IMX6DL 0x61 +#define MXC_CPU_IMX6SX 0x62 +#define MXC_CPU_IMX6Q 0x63 +#define MXC_CPU_IMX6UL 0x64 +#define MXC_CPU_IMX6ULL 0x65 +/* virtual cpu id for i.mx6ulz */ +#define MXC_CPU_IMX6ULZ 0x6b +#define MXC_CPU_IMX6SLL 0x67 +#define MXC_CPU_IMX7D 0x72 +#define MXC_CPU_IMX7ULP 0xff + +#define MXC_CPU_VFx10 0x010 +#define MXC_CPU_VF500 0x500 +#define MXC_CPU_VF510 (MXC_CPU_VF500 | MXC_CPU_VFx10) +#define MXC_CPU_VF600 0x600 +#define MXC_CPU_VF610 (MXC_CPU_VF600 | MXC_CPU_VFx10) + +#ifndef __ASSEMBLY__ +extern unsigned int __mxc_cpu_type; +#endif + +#endif -- cgit v1.3.1