Return-Path: Received: from mx142.netapp.com ([216.240.21.19]:39870 "EHLO mx142.netapp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751211AbcKHR4q (ORCPT ); Tue, 8 Nov 2016 12:56:46 -0500 Subject: Re: net/sunrpc/clnt.c:2773 suspicious rcu_dereference_check() usage! To: Ross Zwisler References: <20161108054202.GA12406@linux.intel.com> <1478606028.2443.2.camel@redhat.com> <1478606957.2443.8.camel@redhat.com> <60a0f29b-7a0a-c5e2-0e98-fa9a923dd339@Netapp.com> <20161108174346.GA17545@linux.intel.com> CC: Jeff Layton , Trond Myklebust , "J. Bruce Fields" , "David S. Miller" , , , , Andy Adamson From: Anna Schumaker Message-ID: <4e93c6f4-ffb1-dc03-0f48-9949f8ef0f49@Netapp.com> Date: Tue, 8 Nov 2016 12:56:14 -0500 MIME-Version: 1.0 In-Reply-To: <20161108174346.GA17545@linux.intel.com> Content-Type: text/plain; charset="utf-8" Sender: linux-nfs-owner@vger.kernel.org List-ID: On 11/08/2016 12:43 PM, Ross Zwisler wrote: > On Tue, Nov 08, 2016 at 07:42:59AM -0500, Anna Schumaker wrote: >> On 11/08/2016 07:09 AM, Jeff Layton wrote: >>> On Tue, 2016-11-08 at 06:53 -0500, Jeff Layton wrote: >>>> On Mon, 2016-11-07 at 22:42 -0700, Ross Zwisler wrote: >>>>> >>>>> 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 >>>> >>>> Thanks Ross, >> >> Hi Ross, >> >> Can you try this patch and let me know if it helps: >> >> http://git.linux-nfs.org/?p=anna/linux-nfs.git;a=commitdiff;h=bb29dd84333a96f309c6d0f88b285b5b78927058 >> >> I'm planning on sending it to Linus soon, so it should be in rc5. > > Hi Anna, > > Yep, this patch makes the warning go away in my setup. Great! Thanks for testing! Anna > > Thanks, > - Ross >