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/rdma/ib.h | 81 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 81 insertions(+) create mode 100644 include/rdma/ib.h (limited to 'include/rdma/ib.h') diff --git a/include/rdma/ib.h b/include/rdma/ib.h new file mode 100644 index 000000000..f7c185ff7 --- /dev/null +++ b/include/rdma/ib.h @@ -0,0 +1,81 @@ +/* SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB */ +/* + * Copyright (c) 2010 Intel Corporation. All rights reserved. + */ + +#ifndef _RDMA_IB_H +#define _RDMA_IB_H + +#include +#include +#include +#include +#include + +struct ib_addr { + union { + __u8 uib_addr8[16]; + __be16 uib_addr16[8]; + __be32 uib_addr32[4]; + __be64 uib_addr64[2]; + } ib_u; +#define sib_addr8 ib_u.uib_addr8 +#define sib_addr16 ib_u.uib_addr16 +#define sib_addr32 ib_u.uib_addr32 +#define sib_addr64 ib_u.uib_addr64 +#define sib_raw ib_u.uib_addr8 +#define sib_subnet_prefix ib_u.uib_addr64[0] +#define sib_interface_id ib_u.uib_addr64[1] +}; + +static inline bool ib_addr_any(const struct ib_addr *a) +{ + return ((a->sib_addr64[0] | a->sib_addr64[1]) == 0); +} + +static inline bool ib_addr_loopback(const struct ib_addr *a) +{ + return ((a->sib_addr32[0] | a->sib_addr32[1] | + a->sib_addr32[2] | (a->sib_addr32[3] ^ htonl(1))) == 0); +} + +static inline void ib_addr_set(struct ib_addr *addr, + __be32 w1, __be32 w2, __be32 w3, __be32 w4) +{ + addr->sib_addr32[0] = w1; + addr->sib_addr32[1] = w2; + addr->sib_addr32[2] = w3; + addr->sib_addr32[3] = w4; +} + +static inline int ib_addr_cmp(const struct ib_addr *a1, const struct ib_addr *a2) +{ + return memcmp(a1, a2, sizeof(struct ib_addr)); +} + +struct sockaddr_ib { + unsigned short int sib_family; /* AF_IB */ + __be16 sib_pkey; + __be32 sib_flowinfo; + struct ib_addr sib_addr; + __be64 sib_sid; + __be64 sib_sid_mask; + __u64 sib_scope_id; +}; + +/* + * The IB interfaces that use write() as bi-directional ioctl() are + * fundamentally unsafe, since there are lots of ways to trigger "write()" + * calls from various contexts with elevated privileges. That includes the + * traditional suid executable error message writes, but also various kernel + * interfaces that can write to file descriptors. + * + * This function provides protection for the legacy API by restricting the + * calling context. + */ +static inline bool ib_safe_file_access(struct file *filp) +{ + return filp->f_cred == current_cred(); +} + +#endif /* _RDMA_IB_H */ -- cgit v1.3.1