From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Fw: [Bug 97811] New: "ip netns create" hangs forever, spamming console with "unregister_netdevice: waiting for lo to become free" Date: Wed, 6 May 2015 10:12:03 -0700 Message-ID: <20150506101203.3ec37196@urahara> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit To: netdev@vger.kernel.org Return-path: Received: from mail-pd0-f170.google.com ([209.85.192.170]:34858 "EHLO mail-pd0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751590AbbEFRMA (ORCPT ); Wed, 6 May 2015 13:12:00 -0400 Received: by pdbqd1 with SMTP id qd1so15388951pdb.2 for ; Wed, 06 May 2015 10:11:59 -0700 (PDT) Received: from urahara (static-50-53-82-155.bvtn.or.frontiernet.net. [50.53.82.155]) by mx.google.com with ESMTPSA id ge4sm2391107pbc.52.2015.05.06.10.11.59 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 06 May 2015 10:11:59 -0700 (PDT) Sender: netdev-owner@vger.kernel.org List-ID: Begin forwarded message: Date: Wed, 6 May 2015 17:09:25 +0000 From: "bugzilla-daemon@bugzilla.kernel.org" To: "shemminger@linux-foundation.org" Subject: [Bug 97811] New: "ip netns create" hangs forever, spamming console with "unregister_netdevice: waiting for lo to become free" https://bugzilla.kernel.org/show_bug.cgi?id=97811 Bug ID: 97811 Summary: "ip netns create" hangs forever, spamming console with "unregister_netdevice: waiting for lo to become free" Product: Networking Version: 2.5 Kernel Version: 4.0.1 Hardware: All OS: Linux Tree: Mainline Status: NEW Severity: normal Priority: P1 Component: Other Assignee: shemminger@linux-foundation.org Reporter: zackw@panix.com Regression: No Created attachment 176051 --> https://bugzilla.kernel.org/attachment.cgi?id=176051&action=edit .config I have an application that makes heavy use of network namespaces, creating and destroying them on the fly during operation. With 100% reproducibility, the first invocation of "ip netns create" after any "ip netns del" hangs forever in D-state; only rebooting the machine clears the condition. (This used to be an intermittent fault, going back at least as far as 3.16, but 4.0 seems to have upgraded it to an every-single-time fault.) lockdep hung task detection reports: May 5 22:48:07 laguz kernel: INFO: task ip:572431 blocked for more than 120 seconds. May 5 22:48:07 laguz kernel: Not tainted 4.0.1-linode55-lockdep #2 May 5 22:48:07 laguz kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. May 5 22:48:07 laguz kernel: ip D ffff88000e28bda8 0 572431 572428 0x00000000 May 5 22:48:07 laguz kernel: ffff88000e28bda8 ffff880058b60000 ffff8801512c6540 ffff88000e28bda8 May 5 22:48:07 laguz kernel: ffff88000e28bfd8 ffff8800a07e6500 ffffffff81ecee88 ffff88000e28be28 May 5 22:48:07 laguz kernel: ffff8801512c6540 ffff88000e28bdc8 ffffffff81964ca9 0000000000000006 May 5 22:48:07 laguz kernel: Call Trace: May 5 22:48:07 laguz kernel: [] schedule+0x74/0x83 May 5 22:48:07 laguz kernel: [] schedule_preempt_disabled+0xe/0x10 May 5 22:48:07 laguz kernel: [] mutex_lock_nested+0x200/0x462 May 5 22:48:07 laguz kernel: [] ? copy_net_ns+0x79/0x103 May 5 22:48:07 laguz kernel: [] ? copy_net_ns+0x44/0x103 May 5 22:48:07 laguz kernel: [] ? lockdep_trace_alloc+0xca/0xdc May 5 22:48:07 laguz kernel: [] copy_net_ns+0x79/0x103 May 5 22:48:07 laguz kernel: [] create_new_namespaces+0x103/0x17f May 5 22:48:07 laguz kernel: [] unshare_nsproxy_namespaces+0x8b/0xb0 May 5 22:48:07 laguz kernel: [] SyS_unshare+0x120/0x2aa May 5 22:48:07 laguz kernel: [] system_call_fastpath+0x12/0x17 May 5 22:48:07 laguz kernel: 1 lock held by ip/572431: May 5 22:48:07 laguz kernel: #0: (net_mutex){+.+.+.}, at: [] copy_net_ns+0x79/0x103 When the bug manifests, there is invariably also a kworker process stuck in D-state, but I don't see anything related to that in this trace. I've restarted the machine so I can continue collecting data, but the condition will recur in a few days, at which point I will provide any additional information that you ask me for between now and then. .config attached. (This is Linode's latest stock 64-bit kernel + activation of lockdep.) -- You are receiving this mail because: You are the assignee for the bug.