Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758626Ab1FBHTE (ORCPT ); Thu, 2 Jun 2011 03:19:04 -0400 Received: from gate.crashing.org ([63.228.1.57]:49065 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757514Ab1FBHTB (ORCPT ); Thu, 2 Jun 2011 03:19:01 -0400 Subject: tty vs workqueue oddities From: Benjamin Herrenschmidt To: Alan Cox Cc: "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset="UTF-8" Date: Thu, 02 Jun 2011 17:17:25 +1000 Message-ID: <1306999045.29297.55.camel@pasglop> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2714 Lines: 53 Hi Alan ! Current upstream (but that's been around for at least 2 or 3 days) seems to have a strange behaviour on one of my powerbooks. Something like "dmesg" or "cat" of a large file in an X terminal "hangs" the machine litterally for minutes. It generally recovers, so not always. Network is unresponsive as well. My attempts at stopping it into xmon always landed in process_one_work() or flush_to_ldisc() from what I can tell, and a simple ftrace run shows something that looks like an -enormous- lot of: kworker/0:1-258 [000] 412.105871: flush_to_ldisc <-process_one_work kworker/0:1-258 [000] 412.105871: tty_ldisc_ref <-flush_to_ldisc kworker/0:1-258 [000] 412.105872: n_tty_receive_buf <-flush_to_ldisc kworker/0:1-258 [000] 412.105872: kill_fasync <-n_tty_receive_buf kworker/0:1-258 [000] 412.105873: __wake_up <-n_tty_receive_buf kworker/0:1-258 [000] 412.105873: __wake_up_common <-__wake_up kworker/0:1-258 [000] 412.105874: default_wake_function <-__wake_up_common kworker/0:1-258 [000] 412.105874: try_to_wake_up <-default_wake_function kworker/0:1-258 [000] 412.105874: tty_throttle <-n_tty_receive_buf kworker/0:1-258 [000] 412.105875: mutex_lock <-tty_throttle kworker/0:1-258 [000] 412.105875: mutex_unlock <-tty_throttle kworker/0:1-258 [000] 412.105876: schedule_work <-flush_to_ldisc kworker/0:1-258 [000] 412.105876: queue_work <-schedule_work kworker/0:1-258 [000] 412.105877: queue_work_on <-queue_work kworker/0:1-258 [000] 412.105877: __queue_work <-queue_work_on kworker/0:1-258 [000] 412.105878: insert_work <-__queue_work kworker/0:1-258 [000] 412.105878: tty_ldisc_deref <-flush_to_ldisc kworker/0:1-258 [000] 412.105879: put_ldisc <-tty_ldisc_deref kworker/0:1-258 [000] 412.105879: __wake_up <-put_ldisc kworker/0:1-258 [000] 412.105880: __wake_up_common <-__wake_up kworker/0:1-258 [000] 412.105880: cwq_dec_nr_in_flight <-process_one_work kworker/0:1-258 [000] 412.105880: process_one_work <-worker_thread and repeat that sequence more/less identical ad nauseum Sometimes it breaks out and makes progress, usually after a few mn. 2.6.39 is fine. I'm going to attempt a bisection but it's a bit slow on those machines and I'm running out of time today, so I wanted to shoot that to you in case it rings a bell. Cheers, Ben. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/