From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758115AbYBWNh7 (ORCPT ); Sat, 23 Feb 2008 08:37:59 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756906AbYBWNhq (ORCPT ); Sat, 23 Feb 2008 08:37:46 -0500 Received: from wx-out-0506.google.com ([66.249.82.226]:51937 "EHLO wx-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756997AbYBWNhb (ORCPT ); Sat, 23 Feb 2008 08:37:31 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:cc:mime-version:content-type:content-transfer-encoding:content-disposition; b=J7MzJKnRcFS/6HOwKwOM/t2DPs5AWRNaIf7I0Mt8cXjzF7pqidBlgT8udVY45r4kjfU9P2GvJ3sm7CCGBKvBBbz2sUjxaHJBeo9aK5rDoGo6UqafUAGW1szXJ4bdoBD4/ZNd+7PDxlhYN8lSq4j/5Njsy7H1k7FxoqIb3nJbSho= Message-ID: <6278d2220802230537m810ce2che694159de3fc3318@mail.gmail.com> Date: Sat, 23 Feb 2008 13:37:29 +0000 From: "Daniel J Blueman" To: "Stephen Oberholtzer" Subject: Re: How to diagnose a process stuck in D state? Cc: "Linux Kernel" MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Stephen, On 22 Feb, 23:10, "Stephen Oberholtzer" wrote: > First off: I'm not subscribed to the list (I don't think I could > handle the volume), so please make sure you CC me if you reply. > > I run an application on one of my machines; it often hangs, with the > process stuck D state. When this happens, the process sticks around > until I reboot the machine. > > I have tried the following to start diagnosing the problem: > > * Running 'ps -axl' shows "-" in the wchan column. > * The contents of /proc/pid/wchan say "_stext". > * 'strace -p pid' says "Process pid attached - interrupt to quit" and > stops responding. Sending SIGINT and SIGTERM have no effect on the > strace process, although kill -11 (SIGSEGV, my personal favorite) does > work. > > This is very confusing. I would greatly appreciate it if someone > could tell me how a process can enter D state without being in a > syscall, and what I can do to start tracking down the cause. wchan shows where the process is sleeping - probably a kernel mutex or lock here. This doesn't help much, but the stack signature will. Enable and use the sys-request mechanism (via terminal, keyboard or serial) eg sysrq-T to dump the stack frames of all processes, including this. Unsurprisingly, it's documented in the kernel Documentation directory. > (By the way: This is on amd64, 2.6.23. I'm updating to 2.6.24.2 right > now, on the off chance that whatever was causing the problem has been > fixed.) Daniel -- Daniel J Blueman