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 --- arch/powerpc/sysdev/ipic.h | 56 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 56 insertions(+) create mode 100644 arch/powerpc/sysdev/ipic.h (limited to 'arch/powerpc/sysdev/ipic.h') diff --git a/arch/powerpc/sysdev/ipic.h b/arch/powerpc/sysdev/ipic.h new file mode 100644 index 000000000..45ab61406 --- /dev/null +++ b/arch/powerpc/sysdev/ipic.h @@ -0,0 +1,56 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +/* + * IPIC private definitions and structure. + * + * Maintainer: Kumar Gala + * + * Copyright 2005 Freescale Semiconductor, Inc + */ +#ifndef __IPIC_H__ +#define __IPIC_H__ + +#include + +#define NR_IPIC_INTS 128 + +/* External IRQS */ +#define IPIC_IRQ_EXT0 48 +#define IPIC_IRQ_EXT1 17 +#define IPIC_IRQ_EXT7 23 + +/* Default Priority Registers */ +#define IPIC_PRIORITY_DEFAULT 0x05309770 + +/* System Global Interrupt Configuration Register */ +#define SICFR_IPSA 0x00010000 +#define SICFR_IPSB 0x00020000 +#define SICFR_IPSC 0x00040000 +#define SICFR_IPSD 0x00080000 +#define SICFR_MPSA 0x00200000 +#define SICFR_MPSB 0x00400000 + +/* System External Interrupt Mask Register */ +#define SEMSR_SIRQ0 0x00008000 + +/* System Error Control Register */ +#define SERCR_MCPR 0x00000001 + +struct ipic { + volatile u32 __iomem *regs; + + /* The remapper for this IPIC */ + struct irq_domain *irqhost; +}; + +struct ipic_info { + u8 ack; /* pending register offset from base if the irq + supports ack operation */ + u8 mask; /* mask register offset from base */ + u8 prio; /* priority register offset from base */ + u8 force; /* force register offset from base */ + u8 bit; /* register bit position (as per doc) + bit mask = 1 << (31 - bit) */ + u8 prio_mask; /* priority mask value */ +}; + +#endif /* __IPIC_H__ */ -- cgit v1.3.1