Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753530Ab2FLWpX (ORCPT ); Tue, 12 Jun 2012 18:45:23 -0400 Received: from mail-lb0-f174.google.com ([209.85.217.174]:46344 "EHLO mail-lb0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751729Ab2FLWpV convert rfc822-to-8bit (ORCPT ); Tue, 12 Jun 2012 18:45:21 -0400 MIME-Version: 1.0 In-Reply-To: <20120612223422.GB13492@fifo99.com> References: <20120612220924.GA13376@fifo99.com> <20120612222912.GB16381@google.com> <20120612223422.GB13492@fifo99.com> Date: Tue, 12 Jun 2012 15:45:20 -0700 Message-ID: Subject: Re: hung_task checking and sys_sync From: Mandeep Baines To: Daniel Walker Cc: fweisbec@gmail.com, sshaiju@mvista.com, mingo@elte.hu, akpm@linux-foundation.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2135 Lines: 54 On Tue, Jun 12, 2012 at 3:34 PM, Daniel Walker wrote: > On Tue, Jun 12, 2012 at 03:29:12PM -0700, Mandeep Singh Baines wrote: >> >> But the time is not unbounded. You could mask the hung_task_detector for >> this case but then you lose the ability to catch bugs in this code path. >> >> The timeout is configurable via /proc/sys/kernel/hung_task_timeout_secs. >> Can you bump up the value at boot via sysctl.conf? > > Maybe, but I'm wondering if these types should just be stopped because Andrew > had complained about them already. > Fair enough. Actually, internally I had a patch where we'd use a task flag to disable and enable the hang check but the approach in the patch you pointed me to seems better. >> > Has there been any commit that disable these messages bdi_sched_wait? >> > >> >> No. There is no mechanism to disable hung_task for a specific code path. >> We do skip processes if PF_PROZEN or PF_FROZEN_SKIP is set but that is >> really a different situation where the wait is unbounded. > > There is presidence for this type of change, > > Author: Mark Lord > Date: ? Fri Sep 24 09:51:13 2010 -0400 > > ? ?block: Prevent hang_check firing during long I/O > > ? ?During long I/O operations, the hang_check timer may fire, > ? ?trigger stack dumps that unnecessarily alarm the user. > > ? ?Eg. ?hdparm --security-erase NULL /dev/sdb ?## can take *hours* to complete > > ? ?So, if hang_check is armed, we should wake up periodically > ? ?to prevent it from triggering. ?This patch uses a wake-up interval > ? ?equal to half the hang_check timer period, which keeps overhead low enough. > > ? ?Signed-off-by: Mark Lord > ? ?Signed-off-by: Jens Axboe > Interesting. I wasn't aware of this patch. Maybe we could abstract this approach via wait_for_completion_no_hang_check(). Regards, Mandeep -- 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/