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/video.h | 136 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 136 insertions(+) create mode 100644 include/asm-generic/video.h (limited to 'include/asm-generic/video.h') diff --git a/include/asm-generic/video.h b/include/asm-generic/video.h new file mode 100644 index 000000000..b1da2309d --- /dev/null +++ b/include/asm-generic/video.h @@ -0,0 +1,136 @@ +/* SPDX-License-Identifier: GPL-2.0 */ + +#ifndef __ASM_GENERIC_VIDEO_H_ +#define __ASM_GENERIC_VIDEO_H_ + +/* + * Only include this header file from your architecture's . + */ + +#include +#include +#include +#include + +struct device; + +#ifndef pgprot_framebuffer +#define pgprot_framebuffer pgprot_framebuffer +static inline pgprot_t pgprot_framebuffer(pgprot_t prot, + unsigned long vm_start, unsigned long vm_end, + unsigned long offset) +{ + return pgprot_writecombine(prot); +} +#endif + +#ifndef video_is_primary_device +#define video_is_primary_device video_is_primary_device +static inline bool video_is_primary_device(struct device *dev) +{ + return false; +} +#endif + +/* + * I/O helpers for the framebuffer. Prefer these functions over their + * regular counterparts. The regular I/O functions provide in-order + * access and swap bytes to/from little-endian ordering. Neither is + * required for framebuffers. Instead, the helpers read and write + * raw framebuffer data. Independent operations can be reordered for + * improved performance. + */ + +#ifndef fb_readb +static inline u8 fb_readb(const volatile void __iomem *addr) +{ + return __raw_readb(addr); +} +#define fb_readb fb_readb +#endif + +#ifndef fb_readw +static inline u16 fb_readw(const volatile void __iomem *addr) +{ + return __raw_readw(addr); +} +#define fb_readw fb_readw +#endif + +#ifndef fb_readl +static inline u32 fb_readl(const volatile void __iomem *addr) +{ + return __raw_readl(addr); +} +#define fb_readl fb_readl +#endif + +#ifndef fb_readq +#if defined(__raw_readq) +static inline u64 fb_readq(const volatile void __iomem *addr) +{ + return __raw_readq(addr); +} +#define fb_readq fb_readq +#endif +#endif + +#ifndef fb_writeb +static inline void fb_writeb(u8 b, volatile void __iomem *addr) +{ + __raw_writeb(b, addr); +} +#define fb_writeb fb_writeb +#endif + +#ifndef fb_writew +static inline void fb_writew(u16 b, volatile void __iomem *addr) +{ + __raw_writew(b, addr); +} +#define fb_writew fb_writew +#endif + +#ifndef fb_writel +static inline void fb_writel(u32 b, volatile void __iomem *addr) +{ + __raw_writel(b, addr); +} +#define fb_writel fb_writel +#endif + +#ifndef fb_writeq +#if defined(__raw_writeq) +static inline void fb_writeq(u64 b, volatile void __iomem *addr) +{ + __raw_writeq(b, addr); +} +#define fb_writeq fb_writeq +#endif +#endif + +#ifndef fb_memcpy_fromio +static inline void fb_memcpy_fromio(void *to, const volatile void __iomem *from, size_t n) +{ + memcpy_fromio(to, from, n); +} +#define fb_memcpy_fromio fb_memcpy_fromio +#endif + +#ifndef fb_memcpy_toio +static inline void fb_memcpy_toio(volatile void __iomem *to, const void *from, size_t n) +{ + memcpy_toio(to, from, n); +} +#define fb_memcpy_toio fb_memcpy_toio +#endif + +#ifndef fb_memset +static inline void fb_memset_io(volatile void __iomem *addr, int c, size_t n) +{ + memset_io(addr, c, n); +} +#define fb_memset fb_memset_io +#endif + +#endif /* __ASM_GENERIC_VIDEO_H_ */ -- cgit v1.3.1