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([2a0d:3344:5521:6b10:58fd:68f:7756:389d]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-47aa039ad21sm59522649f8f.20.2026.07.10.07.20.29 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 10 Jul 2026 07:20:29 -0700 (PDT) Message-ID: <991ec032-c6fe-4236-be22-323a9e3cb07e@redhat.com> Date: Fri, 10 Jul 2026 16:20:28 +0200 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net-next 0/3] vxlan: RCU protect vxlan_config and enable RTNL-less fill_info To: Eric Dumazet , "David S . Miller" , Jakub Kicinski Cc: Simon Horman , Kuniyuki Iwashima , Ido Schimmel , Andrew Lunn , netdev@vger.kernel.org, eric.dumazet@gmail.com References: <20260708160411.1355008-1-edumazet@google.com> From: Paolo Abeni Content-Language: en-US In-Reply-To: <20260708160411.1355008-1-edumazet@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/8/26 6:04 PM, Eric Dumazet wrote: > This patch series converts VXLAN configuration (`struct vxlan_config`) > to be RCU-protected, allowing lockless readers and enabling RTNL-less > `vxlan_fill_info()` netlink link info dumping. > > Work has been split into three distinct parts: > > 1. Refactor helper functions in RX, TX, MDB, VNIFILTER, and OVS paths to > accept a `const struct vxlan_config *cfg` pointer (or pass specific > fields such as `flags`/`saddr_family`) rather than accessing > `vxlan->cfg` directly. > > 2. Convert `vxlan->cfg` from an embedded struct into an RCU-protected > pointer (`struct vxlan_config __rcu *cfg`), dynamically allocated on > device creation or changelink, and freed via `kfree_rcu()`. Update > offload drivers (`mlxsw`) and OVS (`vport-vxlan.c`) accordingly. > > 3. Update `vxlan_fill_info()` to run under `rcu_read_lock()` instead of > relying on RTNL lock, completing the transition to lockless link info > dumping for VXLAN devices. I *suspect* this is triggering RCU splat in forwarding self-tests: [ 1955.481960][T11074] ============================= [ 1955.482076][T11074] WARNING: suspicious RCU usage [ 1955.482190][T11074] 7.2.0-rc2-virtme #1 Not tainted [ 1955.482304][T11074] ----------------------------- [ 1955.482886][T11074] drivers/net/vxlan/vxlan_core.c:1872 suspicious rcu_dereference_check() usage! [ 1955.483087][T11074] [ 1955.483087][T11074] other info that might help us debug this: [ 1955.483087][T11074] [ 1955.483312][T11074] [ 1955.483312][T11074] rcu_scheduler_active = 2, debug_locks = 1 [ 1955.483489][T11074] 1 lock held by arping/11074: [ 1955.483623][T11074] #0: ffffffffbad91d60 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x204/0x1b90 [ 1955.483836][T11074] [ 1955.483836][T11074] stack backtrace: [ 1955.483977][T11074] CPU: 0 UID: 0 PID: 11074 Comm: arping Not tainted 7.2.0-rc2-virtme #1 PREEMPT(full) [ 1955.483980][T11074] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 [ 1955.483982][T11074] Call Trace: [ 1955.483983][T11074] [ 1955.483984][T11074] dump_stack_lvl+0x6f/0xa0 [ 1955.483990][T11074] lockdep_rcu_suspicious.cold+0x37/0x89 [ 1955.483995][T11074] arp_reduce.isra.0+0x9b9/0x1080 [vxlan] [ 1955.484003][T11074] ? mark_usage+0x61/0x170 [ 1955.484007][T11074] ? __lock_acquire+0x518/0xc20 [ 1955.484010][T11074] ? vxlan_nl2conf+0x5b30/0x5b30 [vxlan] [ 1955.484015][T11074] ? lock_acquire.part.0+0xbc/0x260 [ 1955.484017][T11074] ? find_held_lock+0x2b/0x80 [ 1955.484020][T11074] ? __lock_release.isra.0+0x6b/0x1a0 [ 1955.484025][T11074] ? vxlan_xmit+0x128b/0x1660 [vxlan] [ 1955.484029][T11074] vxlan_xmit+0x128b/0x1660 [vxlan] [ 1955.484034][T11074] ? rcu_lockdep_current_cpu_online+0x39/0x1b0 [ 1955.484039][T11074] dev_hard_start_xmit+0xf4/0x620 [ 1955.484042][T11074] ? validate_xmit_skb+0x72/0x9a0 [ 1955.484045][T11074] __dev_queue_xmit+0xc1a/0x1b90 [ 1955.484047][T11074] ? _copy_from_iter+0x1bb/0x1810 [ 1955.484052][T11074] ? __alloc_skb+0x342/0x5f0 [ 1955.484055][T11074] ? _copy_from_iter_flushcache+0x1970/0x1970 [ 1955.484057][T11074] ? ref_tracker_alloc+0x2e7/0x430 [ 1955.484060][T11074] ? netdev_core_pick_tx+0x2c0/0x2c0 [ 1955.484064][T11074] ? packet_parse_headers+0x325/0x830 [ 1955.484067][T11074] ? __asan_memset+0x27/0x50 [ 1955.484070][T11074] ? packet_parse_headers+0x325/0x830 [ 1955.484073][T11074] ? skb_copy_datagram_from_iter+0xf3/0x6a0 [ 1955.484075][T11074] ? packet_release+0xc70/0xc70 [ 1955.484079][T11074] packet_snd+0xfad/0x1990 [ 1955.484085][T11074] ? tpacket_snd+0x19e0/0x19e0 [ 1955.484087][T11074] ? __might_fault+0x97/0x140 [ 1955.484093][T11074] ? __might_fault+0x97/0x140 [ 1955.484095][T11074] ? __might_fault+0x97/0x140 [ 1955.484098][T11074] __sys_sendto+0x2aa/0x400 [ 1955.484101][T11074] ? __ia32_sys_getpeername+0xd0/0xd0 [ 1955.484110][T11074] ? do_user_addr_fault+0x325/0xe30 [ 1955.484116][T11074] __x64_sys_sendto+0xe4/0x1f0 [ 1955.484117][T11074] ? trace_irq_enable.constprop.0+0x9b/0x160 [ 1955.484121][T11074] ? lockdep_hardirqs_on+0x8c/0x130 [ 1955.484123][T11074] ? do_syscall_64+0x82/0x590 [ 1955.484126][T11074] do_syscall_64+0x117/0x590 [ 1955.484127][T11074] ? trace_hardirqs_off+0xd/0x30 [ 1955.484129][T11074] ? exc_page_fault+0xee/0x100 [ 1955.484132][T11074] entry_SYSCALL_64_after_hwframe+0x4b/0x53 [ 1955.484134][T11074] RIP: 0033:0x7f138c3ec54e [ 1955.484138][T11074] Code: 4d 89 d8 e8 b4 bd 00 00 4c 8b 5d f8 41 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 11 c9 c3 0f 1f 80 00 00 00 00 48 8b 45 10 0f 05 c3 83 e2 39 83 fa 08 75 e7 e8 03 ff ff ff 0f 1f 00 f3 0f 1e fa [ 1955.484139][T11074] RSP: 002b:00007ffc648f74e0 EFLAGS: 00000202 ORIG_RAX: 000000000000002c [ 1955.484142][T11074] RAX: ffffffffffffffda RBX: 000000000000001c RCX: 00007f138c3ec54e [ 1955.484143][T11074] RDX: 000000000000001c RSI: 00007ffc648f7560 RDI: 0000000000000005 [ 1955.484144][T11074] RBP: 00007ffc648f74f0 R08: 00007ffc648f79e0 R09: 0000000000000014 [ 1955.484145][T11074] R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000 [ 1955.484146][T11074] R13: 00007ffc648f7910 R14: ffffffffffffffe8 R15: 0000000000000000 full log at: https://netdev-ctrl.bots.linux.dev/logs/vmksft/net-dbg/results/728082/83-test-vxlan-nh-sh/stderr Tentatively setting the series to 'changes requested' /P