Return-Path: Received: from mga02.intel.com ([134.134.136.20]:29449 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752363AbcKHFmF (ORCPT ); Tue, 8 Nov 2016 00:42:05 -0500 Date: Mon, 7 Nov 2016 22:42:02 -0700 From: Ross Zwisler To: Trond Myklebust , Anna Schumaker , "J. Bruce Fields" , Jeff Layton , "David S. Miller" , linux-nfs@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Andy Adamson Subject: net/sunrpc/clnt.c:2773 suspicious rcu_dereference_check() usage! Message-ID: <20161108054202.GA12406@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-nfs-owner@vger.kernel.org List-ID: I've got a virtual machine that has some NFS mounts, and with a newly compiled kernel based on v4.9-rc3 I see the following warning/info message: [ 42.750181] =============================== [ 42.750192] [ INFO: suspicious RCU usage. ] [ 42.750203] 4.9.0-rc3-00002-g7b6e7de #3 Not tainted [ 42.750213] ------------------------------- [ 42.750225] net/sunrpc/clnt.c:2773 suspicious rcu_dereference_check() usage! [ 42.750235] [ 42.750235] other info that might help us debug this: [ 42.750235] [ 42.750246] [ 42.750246] rcu_scheduler_active = 1, debug_locks = 0 [ 42.750257] 1 lock held by mount.nfs4/6440: [ 42.750278] #0: [ 42.750299] ( [ 42.750319] &(&nn->nfs_client_lock)->rlock [ 42.750340] ){+.+...} [ 42.750362] , at: [ 42.750372] [] nfs_get_client+0x105/0x5e0 [ 42.750383] [ 42.750383] stack backtrace: [ 42.750394] CPU: 0 PID: 6440 Comm: mount.nfs4 Not tainted 4.9.0-rc3-00002-g7b6e7de #3 [ 42.750406] Hardware name: Intel Corporation PURLEY/PURLEY, BIOS PLYDCRB1.MBH.0096.D23.1608240105 08/24/2016 [ 42.750429] ffffc9000092fa68 ffffffff8150730f ffff88014ec8da40 0000000000000001 [ 42.750452] ffffc9000092fa98 ffffffff810bc3f7 ffff880150b0b228 ffff88015068dbb0 [ 42.750475] ffffc9000092fb38 ffff88014fc99180 ffffc9000092fac0 ffffffff81b243e5 [ 42.750486] Call Trace: [ 42.750498] [] dump_stack+0x67/0x98 [ 42.750511] [] lockdep_rcu_suspicious+0xe7/0x120 [ 42.750524] [] rpc_clnt_xprt_switch_has_addr+0x115/0x150 [ 42.750536] [] nfs_get_client+0x244/0x5e0 [ 42.750549] [] ? nfs_get_client+0xfc/0x5e0 [ 42.750561] [] nfs4_set_client+0x98/0x130 [ 42.750574] [] nfs4_create_server+0x13e/0x390 [ 42.750588] [] nfs4_remote_mount+0x2e/0x60 [ 42.750600] [] mount_fs+0x39/0x170 [ 42.750614] [] vfs_kern_mount+0x6b/0x150 [ 42.750626] [] ? nfs_do_root_mount+0x3c/0xc0 [ 42.750639] [] nfs_do_root_mount+0x86/0xc0 [ 42.750652] [] nfs4_try_mount+0x44/0xc0 [ 42.750664] [] ? get_nfs_version+0x27/0x90 [ 42.750677] [] nfs_fs_mount+0x4ac/0xd80 [ 42.750689] [] ? lockdep_init_map+0x88/0x1f0 [ 42.750701] [] ? nfs_clone_super+0x130/0x130 [ 42.750713] [] ? param_set_portnr+0x70/0x70 [ 42.750726] [] mount_fs+0x39/0x170 [ 42.750740] [] vfs_kern_mount+0x6b/0x150 [ 42.750752] [] do_mount+0x1f1/0xd10 [ 42.750765] [] ? copy_mount_options+0xa1/0x140 [ 42.750777] [] SyS_mount+0x83/0xd0 [ 42.750790] [] do_syscall_64+0x5c/0x130 [ 42.750802] [] entry_SYSCALL64_slow_path+0x25/0x25 This rcu_dereference_check() was introduced by the following commit: commit 39e5d2df959dd4aea81fa33d765d2a5cc67a0512 Author: Andy Adamson Date: Fri Sep 9 09:22:25 2016 -0400 SUNRPC search xprt switch for sockaddr Signed-off-by: Andy Adamson Signed-off-by: Anna Schumaker Thanks, - Ross