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 --- io_uring/net.h | 79 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 79 insertions(+) create mode 100644 io_uring/net.h (limited to 'io_uring/net.h') diff --git a/io_uring/net.h b/io_uring/net.h new file mode 100644 index 000000000..51fda715d --- /dev/null +++ b/io_uring/net.h @@ -0,0 +1,79 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include +#include +#include +#include + +struct io_async_msghdr { +#if defined(CONFIG_NET) + struct iou_vec vec; + + struct_group(clear, + int namelen; + struct iovec fast_iov; + __kernel_size_t controllen; + __kernel_size_t payloadlen; + struct sockaddr __user *uaddr; + struct msghdr msg; + struct sockaddr_storage addr; + ); +#else + struct_group(clear); +#endif +}; + +#if defined(CONFIG_NET) + +int io_shutdown_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe); +int io_shutdown(struct io_kiocb *req, unsigned int issue_flags); + +void io_sendmsg_recvmsg_cleanup(struct io_kiocb *req); +int io_sendmsg_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe); +int io_sendmsg(struct io_kiocb *req, unsigned int issue_flags); + +int io_send(struct io_kiocb *req, unsigned int issue_flags); + +int io_recvmsg_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe); +int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags); +int io_recv(struct io_kiocb *req, unsigned int issue_flags); + +void io_sendrecv_fail(struct io_kiocb *req); + +int io_accept_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe); +int io_accept(struct io_kiocb *req, unsigned int issue_flags); + +int io_socket_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe); +int io_socket(struct io_kiocb *req, unsigned int issue_flags); +void io_socket_bpf_populate(struct io_uring_bpf_ctx *bctx, struct io_kiocb *req); +void io_connect_bpf_populate(struct io_uring_bpf_ctx *bctx, struct io_kiocb *req); + +int io_connect_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe); +int io_connect(struct io_kiocb *req, unsigned int issue_flags); + +int io_sendmsg_zc(struct io_kiocb *req, unsigned int issue_flags); +int io_send_zc_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe); +void io_send_zc_cleanup(struct io_kiocb *req); + +int io_bind_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe); +int io_bind(struct io_kiocb *req, unsigned int issue_flags); + +int io_listen_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe); +int io_listen(struct io_kiocb *req, unsigned int issue_flags); + +void io_netmsg_cache_free(const void *entry); +#else +static inline void io_netmsg_cache_free(const void *entry) +{ +} +static inline void io_socket_bpf_populate(struct io_uring_bpf_ctx *bctx, + struct io_kiocb *req) +{ +} + +static inline void io_connect_bpf_populate(struct io_uring_bpf_ctx *bctx, + struct io_kiocb *req) +{ +} + +#endif -- cgit v1.3.1