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 --- net/9p/Kconfig | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 63 insertions(+) create mode 100644 net/9p/Kconfig (limited to 'net/9p/Kconfig') diff --git a/net/9p/Kconfig b/net/9p/Kconfig new file mode 100644 index 000000000..22f8c1678 --- /dev/null +++ b/net/9p/Kconfig @@ -0,0 +1,63 @@ +# SPDX-License-Identifier: GPL-2.0-only +# +# 9P protocol configuration +# + +menuconfig NET_9P + tristate "Plan 9 Resource Sharing Support (9P2000)" + select NETFS_SUPPORT + help + If you say Y here, you will get experimental support for + Plan 9 resource sharing via the 9P2000 protocol. + + See for more information. + + If unsure, say N. + +if NET_9P + +config NET_9P_FD + default NET_9P + imply INET + imply UNIX + tristate "9P FD Transport" + help + This builds support for transports over TCP, Unix sockets and + filedescriptors. + +config NET_9P_VIRTIO + depends on VIRTIO + tristate "9P Virtio Transport" + help + This builds support for a transports between + guest partitions and a host partition. + +config NET_9P_XEN + depends on XEN + select XEN_XENBUS_FRONTEND + tristate "9P Xen Transport" + help + This builds support for a transport for 9pfs between + two Xen domains. + +config NET_9P_USBG + tristate "9P USB Gadget Transport" + depends on USB_GADGET + select CONFIGFS_FS + select USB_LIBCOMPOSITE + help + This builds support for a transport for 9pfs over + usb gadget. + +config NET_9P_RDMA + depends on INET && INFINIBAND && INFINIBAND_ADDR_TRANS + tristate "9P RDMA Transport (Experimental)" + help + This builds support for an RDMA transport. + +config NET_9P_DEBUG + bool "Debug information" + help + Say Y if you want the 9P subsystem to log debug information. + +endif -- cgit v1.3.1