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/sctp/primitive.c | 201 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 201 insertions(+) create mode 100644 net/sctp/primitive.c (limited to 'net/sctp/primitive.c') diff --git a/net/sctp/primitive.c b/net/sctp/primitive.c new file mode 100644 index 000000000..782d673c3 --- /dev/null +++ b/net/sctp/primitive.c @@ -0,0 +1,201 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* SCTP kernel implementation + * Copyright (c) 1999-2000 Cisco, Inc. + * Copyright (c) 1999-2001 Motorola, Inc. + * + * This file is part of the SCTP kernel implementation + * + * These functions implement the SCTP primitive functions from Section 10. + * + * Note that the descriptions from the specification are USER level + * functions--this file is the functions which populate the struct proto + * for SCTP which is the BOTTOM of the sockets interface. + * + * Please send any bug reports or fixes you make to the + * email address(es): + * lksctp developers + * + * Written or modified by: + * La Monte H.P. Yarroll + * Narasimha Budihal + * Karl Knutson + * Ardelle Fan + * Kevin Gao + */ + +#include +#include /* For struct list_head */ +#include +#include +#include /* For struct timeval */ +#include +#include +#include +#include + +#define DECLARE_PRIMITIVE(name) \ +/* This is called in the code as sctp_primitive_ ## name. */ \ +int sctp_primitive_ ## name(struct net *net, struct sctp_association *asoc, \ + void *arg) { \ + int error = 0; \ + enum sctp_event_type event_type; union sctp_subtype subtype; \ + enum sctp_state state; \ + struct sctp_endpoint *ep; \ + \ + event_type = SCTP_EVENT_T_PRIMITIVE; \ + subtype = SCTP_ST_PRIMITIVE(SCTP_PRIMITIVE_ ## name); \ + state = asoc ? asoc->state : SCTP_STATE_CLOSED; \ + ep = asoc ? asoc->ep : NULL; \ + \ + error = sctp_do_sm(net, event_type, subtype, state, ep, asoc, \ + arg, GFP_KERNEL); \ + return error; \ +} + +/* 10.1 ULP-to-SCTP + * B) Associate + * + * Format: ASSOCIATE(local SCTP instance name, destination transport addr, + * outbound stream count) + * -> association id [,destination transport addr list] [,outbound stream + * count] + * + * This primitive allows the upper layer to initiate an association to a + * specific peer endpoint. + * + * This version assumes that asoc is fully populated with the initial + * parameters. We then return a traditional kernel indicator of + * success or failure. + */ + +/* This is called in the code as sctp_primitive_ASSOCIATE. */ + +DECLARE_PRIMITIVE(ASSOCIATE) + +/* 10.1 ULP-to-SCTP + * C) Shutdown + * + * Format: SHUTDOWN(association id) + * -> result + * + * Gracefully closes an association. Any locally queued user data + * will be delivered to the peer. The association will be terminated only + * after the peer acknowledges all the SCTP packets sent. A success code + * will be returned on successful termination of the association. If + * attempting to terminate the association results in a failure, an error + * code shall be returned. + */ + +DECLARE_PRIMITIVE(SHUTDOWN); + +/* 10.1 ULP-to-SCTP + * C) Abort + * + * Format: Abort(association id [, cause code]) + * -> result + * + * Ungracefully closes an association. Any locally queued user data + * will be discarded and an ABORT chunk is sent to the peer. A success + * code will be returned on successful abortion of the association. If + * attempting to abort the association results in a failure, an error + * code shall be returned. + */ + +DECLARE_PRIMITIVE(ABORT); + +/* 10.1 ULP-to-SCTP + * E) Send + * + * Format: SEND(association id, buffer address, byte count [,context] + * [,stream id] [,life time] [,destination transport address] + * [,unorder flag] [,no-bundle flag] [,payload protocol-id] ) + * -> result + * + * This is the main method to send user data via SCTP. + * + * Mandatory attributes: + * + * o association id - local handle to the SCTP association + * + * o buffer address - the location where the user message to be + * transmitted is stored; + * + * o byte count - The size of the user data in number of bytes; + * + * Optional attributes: + * + * o context - an optional 32 bit integer that will be carried in the + * sending failure notification to the ULP if the transportation of + * this User Message fails. + * + * o stream id - to indicate which stream to send the data on. If not + * specified, stream 0 will be used. + * + * o life time - specifies the life time of the user data. The user data + * will not be sent by SCTP after the life time expires. This + * parameter can be used to avoid efforts to transmit stale + * user messages. SCTP notifies the ULP if the data cannot be + * initiated to transport (i.e. sent to the destination via SCTP's + * send primitive) within the life time variable. However, the + * user data will be transmitted if SCTP has attempted to transmit a + * chunk before the life time expired. + * + * o destination transport address - specified as one of the destination + * transport addresses of the peer endpoint to which this packet + * should be sent. Whenever possible, SCTP should use this destination + * transport address for sending the packets, instead of the current + * primary path. + * + * o unorder flag - this flag, if present, indicates that the user + * would like the data delivered in an unordered fashion to the peer + * (i.e., the U flag is set to 1 on all DATA chunks carrying this + * message). + * + * o no-bundle flag - instructs SCTP not to bundle this user data with + * other outbound DATA chunks. SCTP MAY still bundle even when + * this flag is present, when faced with network congestion. + * + * o payload protocol-id - A 32 bit unsigned integer that is to be + * passed to the peer indicating the type of payload protocol data + * being transmitted. This value is passed as opaque data by SCTP. + */ + +DECLARE_PRIMITIVE(SEND); + +/* 10.1 ULP-to-SCTP + * J) Request Heartbeat + * + * Format: REQUESTHEARTBEAT(association id, destination transport address) + * + * -> result + * + * Instructs the local endpoint to perform a HeartBeat on the specified + * destination transport address of the given association. The returned + * result should indicate whether the transmission of the HEARTBEAT + * chunk to the destination address is successful. + * + * Mandatory attributes: + * + * o association id - local handle to the SCTP association + * + * o destination transport address - the transport address of the + * association on which a heartbeat should be issued. + */ + +DECLARE_PRIMITIVE(REQUESTHEARTBEAT); + +/* ADDIP +* 3.1.1 Address Configuration Change Chunk (ASCONF) +* +* This chunk is used to communicate to the remote endpoint one of the +* configuration change requests that MUST be acknowledged. The +* information carried in the ASCONF Chunk uses the form of a +* Type-Length-Value (TLV), as described in "3.2.1 Optional/ +* Variable-length Parameter Format" in RFC2960 [5], forall variable +* parameters. +*/ + +DECLARE_PRIMITIVE(ASCONF); + +/* RE-CONFIG 5.1 */ +DECLARE_PRIMITIVE(RECONF); -- cgit v1.3.1