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/rtc/rtc-s3c.h | 48 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 48 insertions(+) create mode 100644 drivers/rtc/rtc-s3c.h (limited to 'drivers/rtc/rtc-s3c.h') diff --git a/drivers/rtc/rtc-s3c.h b/drivers/rtc/rtc-s3c.h new file mode 100644 index 000000000..11d7a1255 --- /dev/null +++ b/drivers/rtc/rtc-s3c.h @@ -0,0 +1,48 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Copyright (c) 2003 Simtec Electronics + * http://www.simtec.co.uk/products/SWLINUX/ + * + * S3C2410 Internal RTC register definition +*/ + +#ifndef __ASM_ARCH_REGS_RTC_H +#define __ASM_ARCH_REGS_RTC_H __FILE__ + +#define S3C2410_RTCREG(x) (x) +#define S3C2410_INTP S3C2410_RTCREG(0x30) +#define S3C2410_INTP_ALM (1 << 1) +#define S3C2410_INTP_TIC (1 << 0) + +#define S3C2410_RTCCON S3C2410_RTCREG(0x40) +#define S3C2410_RTCCON_RTCEN (1 << 0) +#define S3C2410_RTCCON_CNTSEL (1 << 2) +#define S3C2410_RTCCON_CLKRST (1 << 3) +#define S3C2443_RTCCON_TICSEL (1 << 4) +#define S3C64XX_RTCCON_TICEN (1 << 8) + +#define S3C2410_RTCALM S3C2410_RTCREG(0x50) +#define S3C2410_RTCALM_ALMEN (1 << 6) +#define S3C2410_RTCALM_YEAREN (1 << 5) +#define S3C2410_RTCALM_MONEN (1 << 4) +#define S3C2410_RTCALM_DAYEN (1 << 3) +#define S3C2410_RTCALM_HOUREN (1 << 2) +#define S3C2410_RTCALM_MINEN (1 << 1) +#define S3C2410_RTCALM_SECEN (1 << 0) + +#define S3C2410_ALMSEC S3C2410_RTCREG(0x54) +#define S3C2410_ALMMIN S3C2410_RTCREG(0x58) +#define S3C2410_ALMHOUR S3C2410_RTCREG(0x5c) + +#define S3C2410_ALMDATE S3C2410_RTCREG(0x60) +#define S3C2410_ALMMON S3C2410_RTCREG(0x64) +#define S3C2410_ALMYEAR S3C2410_RTCREG(0x68) + +#define S3C2410_RTCSEC S3C2410_RTCREG(0x70) +#define S3C2410_RTCMIN S3C2410_RTCREG(0x74) +#define S3C2410_RTCHOUR S3C2410_RTCREG(0x78) +#define S3C2410_RTCDATE S3C2410_RTCREG(0x7c) +#define S3C2410_RTCMON S3C2410_RTCREG(0x84) +#define S3C2410_RTCYEAR S3C2410_RTCREG(0x88) + +#endif /* __ASM_ARCH_REGS_RTC_H */ -- cgit v1.3.1