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/lib/pmem.c | 88 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 88 insertions(+) create mode 100644 arch/powerpc/lib/pmem.c (limited to 'arch/powerpc/lib/pmem.c') diff --git a/arch/powerpc/lib/pmem.c b/arch/powerpc/lib/pmem.c new file mode 100644 index 000000000..0f0f2d851 --- /dev/null +++ b/arch/powerpc/lib/pmem.c @@ -0,0 +1,88 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright(c) 2017 IBM Corporation. All rights reserved. + */ + +#include +#include +#include +#include + +#include + +static inline void __clean_pmem_range(unsigned long start, unsigned long stop) +{ + unsigned long shift = l1_dcache_shift(); + unsigned long bytes = l1_dcache_bytes(); + void *addr = (void *)(start & ~(bytes - 1)); + unsigned long size = stop - (unsigned long)addr + (bytes - 1); + unsigned long i; + + for (i = 0; i < size >> shift; i++, addr += bytes) + asm volatile(PPC_DCBSTPS(%0, %1): :"i"(0), "r"(addr): "memory"); +} + +static inline void __flush_pmem_range(unsigned long start, unsigned long stop) +{ + unsigned long shift = l1_dcache_shift(); + unsigned long bytes = l1_dcache_bytes(); + void *addr = (void *)(start & ~(bytes - 1)); + unsigned long size = stop - (unsigned long)addr + (bytes - 1); + unsigned long i; + + for (i = 0; i < size >> shift; i++, addr += bytes) + asm volatile(PPC_DCBFPS(%0, %1): :"i"(0), "r"(addr): "memory"); +} + +static inline void clean_pmem_range(unsigned long start, unsigned long stop) +{ + if (cpu_has_feature(CPU_FTR_ARCH_207S)) + return __clean_pmem_range(start, stop); +} + +static inline void flush_pmem_range(unsigned long start, unsigned long stop) +{ + if (cpu_has_feature(CPU_FTR_ARCH_207S)) + return __flush_pmem_range(start, stop); +} + +/* + * CONFIG_ARCH_HAS_PMEM_API symbols + */ +void arch_wb_cache_pmem(void *addr, size_t size) +{ + unsigned long start = (unsigned long) addr; + clean_pmem_range(start, start + size); +} +EXPORT_SYMBOL_GPL(arch_wb_cache_pmem); + +void arch_invalidate_pmem(void *addr, size_t size) +{ + unsigned long start = (unsigned long) addr; + flush_pmem_range(start, start + size); +} +EXPORT_SYMBOL_GPL(arch_invalidate_pmem); + +/* + * CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE symbols + */ +size_t copy_from_user_flushcache(void *dest, const void __user *src, + size_t size) +{ + unsigned long not_copied, start = (unsigned long) dest; + + src = mask_user_address(src); + not_copied = __copy_from_user(dest, src, size); + clean_pmem_range(start, start + size); + + return not_copied; +} + +void memcpy_flushcache(void *dest, const void *src, size_t size) +{ + unsigned long start = (unsigned long) dest; + + memcpy(dest, src, size); + clean_pmem_range(start, start + size); +} +EXPORT_SYMBOL(memcpy_flushcache); -- cgit v1.3.1