Messages in this thread | | | Date | Wed, 18 Oct 2006 09:37:58 +0530 | From | Srinivasa Ds <> | Subject | Issues with possible recursive locking |
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When I was removing dlm module,I hit in to below error.
========================================== [ INFO: possible recursive locking detected ]
2.6.18#1 --------------------------------------------- modprobe/4501 is trying to acquire lock: (&inode->i_mutex){--..}, at: [<c0611e5a>] mutex_lock+0x21/0x24
but task is already holding lock: (&inode->i_mutex){--..}, at: [<c0611e5a>] mutex_lock+0x21/0x24
other info that might help us debug this: 1 lock held by modprobe/4501: #0: (&inode->i_mutex){--..}, at: [<c0611e5a>] mutex_lock+0x21/0x24
stack backtrace: [<c04051ed>] show_trace_log_lvl+0x58/0x16a [<c04057fa>] show_trace+0xd/0x10 [<c0405913>] dump_stack+0x19/0x1b [<c043b6f1>] __lock_acquire+0x778/0x99c [<c043be86>] lock_acquire+0x4b/0x6d [<c0611ceb>] __mutex_lock_slowpath+0xbc/0x20a [<c0611e5a>] mutex_lock+0x21/0x24 [<f89c2562>] configfs_unregister_subsystem+0x3e/0xa8 [configfs] [<f8f4263f>] dlm_config_exit+0xd/0xf [dlm] [<f8f4db94>] exit_dlm+0x12/0x23 [dlm] [<c0442790>] sys_delete_module+0x18d/0x1b5 [<c0403fb7>] syscall_call+0x7/0xb =========================================================== Cause for this problem is, lock-validator validates the locks through lock class. And by definition,a lock in struct inode considered as one class, irrespective of number of of instances of different inode present in the system. Hence 2 consecutive mutex lock on d_inode->i_mutex considered as recursive lock,eventhough both inodes are different. Thats what happening below. Is it not a kernel design constraint ??
============================================== void configfs_unregister_subsystem(struct configfs_subsystem *subsys) { struct config_group *group = &subsys->su_group; struct dentry *dentry = group->cg_item.ci_dentry;
if (dentry->d_parent != configfs_sb->s_root) { printk(KERN_ERR "configfs: Tried to unregister non-subsystem!\n"); return; }
mutex_lock(&configfs_sb->s_root->d_inode->i_mutex); mutex_lock(&dentry->d_inode->i_mutex); ==> problem is here if (configfs_detach_prep(dentry)) { printk(KERN_ERR "configfs: Tried to unregister non-empty subsystem!\n"); } ===========================================
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