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/asm-generic/iomap.h | 95 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 95 insertions(+) create mode 100644 include/asm-generic/iomap.h (limited to 'include/asm-generic/iomap.h') diff --git a/include/asm-generic/iomap.h b/include/asm-generic/iomap.h new file mode 100644 index 000000000..9f3f25d7f --- /dev/null +++ b/include/asm-generic/iomap.h @@ -0,0 +1,95 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __GENERIC_IO_H +#define __GENERIC_IO_H + +#include +#include + +/* + * These are the "generic" interfaces for doing new-style + * memory-mapped or PIO accesses. Architectures may do + * their own arch-optimized versions, these just act as + * wrappers around the old-style IO register access functions: + * read[bwl]/write[bwl]/in[bwl]/out[bwl] + * + * Don't include this directly, include it from . + */ + +/* + * Read/write from/to an (offsettable) iomem cookie. It might be a PIO + * access or a MMIO access, these functions don't care. The info is + * encoded in the hardware mapping set up by the mapping functions + * (or the cookie itself, depending on implementation and hw). + * + * The generic routines just encode the PIO/MMIO as part of the + * cookie, and coldly assume that the MMIO IO mappings are not + * in the low address range. Architectures for which this is not + * true can't use this generic implementation. + */ +extern unsigned int ioread8(const void __iomem *); +extern unsigned int ioread16(const void __iomem *); +extern unsigned int ioread16be(const void __iomem *); +extern unsigned int ioread32(const void __iomem *); +extern unsigned int ioread32be(const void __iomem *); + +extern u64 __ioread64_lo_hi(const void __iomem *addr); +extern u64 __ioread64_hi_lo(const void __iomem *addr); +extern u64 __ioread64be_lo_hi(const void __iomem *addr); +extern u64 __ioread64be_hi_lo(const void __iomem *addr); + +extern void iowrite8(u8, void __iomem *); +extern void iowrite16(u16, void __iomem *); +extern void iowrite16be(u16, void __iomem *); +extern void iowrite32(u32, void __iomem *); +extern void iowrite32be(u32, void __iomem *); + +extern void __iowrite64_lo_hi(u64 val, void __iomem *addr); +extern void __iowrite64_hi_lo(u64 val, void __iomem *addr); +extern void __iowrite64be_lo_hi(u64 val, void __iomem *addr); +extern void __iowrite64be_hi_lo(u64 val, void __iomem *addr); + +/* + * "string" versions of the above. Note that they + * use native byte ordering for the accesses (on + * the assumption that IO and memory agree on a + * byte order, and CPU byteorder is irrelevant). + * + * They do _not_ update the port address. If you + * want MMIO that copies stuff laid out in MMIO + * memory across multiple ports, use "memcpy_toio()" + * and friends. + */ +extern void ioread8_rep(const void __iomem *port, void *buf, unsigned long count); +extern void ioread16_rep(const void __iomem *port, void *buf, unsigned long count); +extern void ioread32_rep(const void __iomem *port, void *buf, unsigned long count); + +extern void iowrite8_rep(void __iomem *port, const void *buf, unsigned long count); +extern void iowrite16_rep(void __iomem *port, const void *buf, unsigned long count); +extern void iowrite32_rep(void __iomem *port, const void *buf, unsigned long count); + +#ifdef CONFIG_HAS_IOPORT_MAP +/* Create a virtual mapping cookie for an IO port range */ +extern void __iomem *ioport_map(unsigned long port, unsigned int nr); +extern void ioport_unmap(void __iomem *); +#endif + +#ifndef ioremap_wc +#define ioremap_wc ioremap +#endif + +#ifndef ioremap_wt +#define ioremap_wt ioremap +#endif + +#ifndef ioremap_np +/* See the comment in asm-generic/io.h about ioremap_np(). */ +#define ioremap_np ioremap_np +static inline void __iomem *ioremap_np(phys_addr_t offset, size_t size) +{ + return NULL; +} +#endif + +#include + +#endif -- cgit v1.3.1