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/can/Kconfig | 73 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 73 insertions(+) create mode 100644 net/can/Kconfig (limited to 'net/can/Kconfig') diff --git a/net/can/Kconfig b/net/can/Kconfig new file mode 100644 index 000000000..abbb4be7a --- /dev/null +++ b/net/can/Kconfig @@ -0,0 +1,73 @@ +# SPDX-License-Identifier: GPL-2.0-only +# +# Controller Area Network (CAN) network layer core configuration +# + +menuconfig CAN + tristate "CAN bus subsystem support" + select SKB_EXTENSIONS + help + Controller Area Network (CAN) is a slow (up to 1Mbit/s) serial + communications protocol. Development of the CAN bus started in + 1983 at Robert Bosch GmbH, and the protocol was officially + released in 1986. The CAN bus was originally mainly for automotive, + but is now widely used in marine (NMEA2000), industrial, and medical + applications. More information on the CAN network protocol family + PF_CAN is contained in . + + If you want CAN support you should say Y here and also to the + specific driver for your controller(s) under the Network device + support section. + +if CAN + +config CAN_RAW + tristate "Raw CAN Protocol (raw access with CAN-ID filtering)" + default y + help + The raw CAN protocol option offers access to the CAN bus via + the BSD socket API. You probably want to use the raw socket in + most cases where no higher level protocol is being used. The raw + socket has several filter options e.g. ID masking / error frames. + To receive/send raw CAN messages, use AF_CAN with protocol CAN_RAW. + +config CAN_BCM + tristate "Broadcast Manager CAN Protocol (with content filtering)" + default y + help + The Broadcast Manager offers content filtering, timeout monitoring, + sending of RTR frames, and cyclic CAN messages without permanent user + interaction. The BCM can be 'programmed' via the BSD socket API and + informs you on demand e.g. only on content updates / timeouts. + You probably want to use the bcm socket in most cases where cyclic + CAN messages are used on the bus (e.g. in automotive environments). + To use the Broadcast Manager, use AF_CAN with protocol CAN_BCM. + +config CAN_GW + tristate "CAN Gateway/Router (with netlink configuration)" + default y + help + The CAN Gateway/Router is used to route (and modify) CAN frames. + It is based on the PF_CAN core infrastructure for msg filtering and + msg sending and can optionally modify routed CAN frames on the fly. + CAN frames can be routed between CAN network interfaces (one hop). + They can be modified with AND/OR/XOR/SET operations as configured + by the netlink configuration interface known e.g. from iptables. + +source "net/can/j1939/Kconfig" + +config CAN_ISOTP + tristate "ISO 15765-2 CAN transport protocol" + help + CAN Transport Protocols offer support for segmented Point-to-Point + communication between CAN nodes via two defined CAN Identifiers. + This protocol driver implements segmented data transfers for CAN CC + (aka Classical CAN, CAN 2.0B) and CAN FD frame types which were + introduced with ISO 15765-2:2016. + As CAN frames can only transport a small amount of data bytes + (max. 8 bytes for CAN CC and max. 64 bytes for CAN FD) this + segmentation is needed to transport longer Protocol Data Units (PDU) + as needed e.g. for vehicle diagnosis (UDS, ISO 14229) or IP-over-CAN + traffic. + +endif -- cgit v1.3.1