From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bart Van Assche Subject: Re: [PATCH-v2 2/4] target: Drop lun_sep_lock for se_lun->lun_se_dev RCU usage Date: Tue, 26 May 2015 16:30:12 +0200 Message-ID: <55648374.80802@sandisk.com> References: <1432623445-25776-1-git-send-email-nab@daterainc.com> <1432623445-25776-3-git-send-email-nab@daterainc.com> Mime-Version: 1.0 Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1432623445-25776-3-git-send-email-nab@daterainc.com> Sender: target-devel-owner@vger.kernel.org To: "Nicholas A. Bellinger" , target-devel Cc: linux-scsi , linux-kernel , Christoph Hellwig , Hannes Reinecke , Sagi Grimberg , "Paul E. McKenney" , Nicholas Bellinger List-Id: linux-scsi@vger.kernel.org On 05/26/15 08:57, Nicholas A. Bellinger wrote: > @@ -625,6 +626,7 @@ int core_dev_add_initiator_node_lun_acl( > u32 lun_access) > { > struct se_node_acl *nacl = lacl->se_lun_nacl; > + struct se_device *dev = lockless_dereference(lun->lun_se_dev); > > if (!nacl) > return -EINVAL; An attempt to run this code on a system with RCU debugging enabled resulted in the following complaint: =============================== [ INFO: suspicious RCU usage. ] 4.1.0-rc1-lio-dbg+ #1 Not tainted ------------------------------- drivers/target/target_core_device.c:617 suspicious rcu_dereference_check() usage! other info that might help us debug this: rcu_scheduler_active = 1, debug_locks = 1 2 locks held by ln/1497: #0: (sb_writers#11){.+.+.+}, at: [] mnt_want_write+0x24/0x50 #1: (&sb->s_type->i_mutex_key#14/1){+.+.+.}, at: [] filename_create+0xad/0x1a0 stack backtrace: CPU: 0 PID: 1497 Comm: ln Not tainted 4.1.0-rc1-lio-dbg+ #1 Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 0000000000000001 ffff88005955bd68 ffffffff814fa346 0000000000000011 ffff880058bf1270 ffff88005955bd98 ffffffff810ab235 ffff880050db9a68 ffff880058ae2e68 0000000000000002 ffff880058ae4120 ffff88005955be08 Call Trace: [] dump_stack+0x4f/0x7b [] lockdep_rcu_suspicious+0xd5/0x110 [] core_dev_add_initiator_node_lun_acl+0xec/0x190 [target_core_mod] [] ? get_parent_ip+0x11/0x50 [] target_fabric_mappedlun_link+0x129/0x240 [target_core_mod] [] ? target_fabric_mappedlun_link+0x9c/0x240 [target_core_mod] [] configfs_symlink+0x13d/0x360 [configfs] [] vfs_symlink+0x58/0xb0 [] SyS_symlink+0x65/0xc0 [] system_call_fastpath+0x16/0x7a