From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750974AbdEaDss (ORCPT ); Tue, 30 May 2017 23:48:48 -0400 Received: from outbound.smtp.vt.edu ([198.82.183.121]:37848 "EHLO omr1.cc.vt.edu" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750811AbdEaDsr (ORCPT ); Tue, 30 May 2017 23:48:47 -0400 X-Mailer: exmh version 2.8.0 04/21/2017 with nmh-1.6+dev From: valdis.kletnieks@vt.edu To: Vegard Nossum , Greg Kroah-Hartman Cc: linux-kernel@vger.kernel.org, Jiri Slaby Subject: linux-next 20170519 and later - ^S/^Q borkage on ttys. Mime-Version: 1.0 Content-Type: multipart/signed; boundary="==_Exmh_1496202518_18763P"; micalg=pgp-sha1; protocol="application/pgp-signature" Content-Transfer-Encoding: 7bit Date: Tue, 30 May 2017 23:48:38 -0400 Message-ID: <22119.1496202518@turing-police.cc.vt.edu> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --==_Exmh_1496202518_18763P Content-Type: text/plain; charset=us-ascii Pretty drastic. Hit ^S to pause scrolling, and instantly hung terminal. Seen on both urxvt and xterm under x11, and on virtual console screens. This appears in dmesg: [ 1844.182058] INFO: task kworker/u8:3:129 blocked for more than 120 seconds. [ 1844.182073] Tainted: G OE 4.12.0-rc3-next-20170530 #489 [ 1844.182078] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 1844.182085] kworker/u8:3 D11008 129 2 0x00000000 [ 1844.182109] Workqueue: events_unbound flush_to_ldisc [ 1844.182118] Call Trace: [ 1844.182136] __schedule+0x43e/0x1020 [ 1844.182147] ? schedule_preempt_disabled+0x27/0xd0 [ 1844.182156] schedule+0x5d/0x1d0 [ 1844.182164] ? __mutex_lock+0x4c9/0x11c0 [ 1844.182172] schedule_preempt_disabled+0x27/0xd0 [ 1844.182179] __mutex_lock+0x4c9/0x11c0 [ 1844.182191] ? tty_port_default_receive_buf+0x58/0xc0 [ 1844.182204] ? ldsem_down_read_trylock+0xc3/0x130 [ 1844.182215] mutex_lock_nested+0x1b/0x20 [ 1844.182222] ? mutex_lock_nested+0x1b/0x20 [ 1844.182230] tty_port_default_receive_buf+0x58/0xc0 [ 1844.182240] flush_to_ldisc+0xea/0x220 [ 1844.182249] ? trace_hardirqs_on_caller+0x16/0x290 [ 1844.182262] process_one_work+0x3d6/0xd00 [ 1844.182269] ? lock_acquire+0xae/0x2f0 [ 1844.182284] worker_thread+0x71/0x830 [ 1844.182297] kthread+0x1a9/0x270 [ 1844.182304] ? process_one_work+0xd00/0xd00 [ 1844.182310] ? kthread_create_on_node+0x70/0x70 [ 1844.182321] ret_from_fork+0x27/0x40 [ 1844.182608] INFO: lockdep is turned off. Bisects down to this commit, and things work when it's reverted. Commit 925bb1ce47f4. Author: Vegard Nossum Date: Thu May 11 12:18:52 2017 +0200 tty: fix port buffer locking tty_insert_flip_string_fixed_flag() is racy against itself when called from the ioctl(TCXONC, TCION/TCIOFF) path [1] and the flush_to_ldisc() workqueue path [2]. --==_Exmh_1496202518_18763P Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Comment: Exmh version 2.8.0 04/21/2017 iQEVAwUBWS49Fo0DS38y7CIcAQJkowf9FlovfNTMYs4sHjmEno1hMOtoOIJ1i+/j PtARLbvVW1WtIkHHF9Z+qJVSY9hpjYeE0jhwrQC6myS5erLPK+8+u5DO+fhZorCP 4NNBC6yCzcb0Bk2R0cNwzCxY1QdyErrKQYrokf5I22xJ3UC7+93drTlW2bXs+khw l7Pm8seCj4Lhwg/ABD1PbZqDMFmN8TTBgNsQ6yNcVLdm0S/htcPFT7yFN+Jyy369 kBRftWfCR3WYSu6bRZfFJ2dSIzF3Tc0U8qQDkTSSRjKY2tzNhuwjkU3+HeXtOG0F sEM4Y/kUFna4RhkeJkTiShT+5SSIpbzIFBuzRxF+nmIGlBSbw3lJ+w== =jiFT -----END PGP SIGNATURE----- --==_Exmh_1496202518_18763P--