From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754845Ab1EKT3K (ORCPT ); Wed, 11 May 2011 15:29:10 -0400 Received: from mail-ew0-f46.google.com ([209.85.215.46]:47361 "EHLO mail-ew0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754533Ab1EKT3I (ORCPT ); Wed, 11 May 2011 15:29:08 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=r3AElS+px40Vov6eQcLlDX4ot9aQLwrPP+XByxECrFo5kVSYfSZ6zhTxr0YcmK+PGT mhpHElBw0rnP4hVaxQJEeszMJOkTN6RvIE/5yk6x17QlAVJaYQ65LwL+MPB8aIfY1NGC ik2tN4bn0d0icDsG0pdK4BPz5C8kg+cw797Co= Date: Wed, 11 May 2011 21:29:02 +0200 From: Tejun Heo To: Oleg Nesterov Cc: jan.kratochvil@redhat.com, vda.linux@googlemail.com, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, indan@nul.nu Subject: Re: [PATCH 09/11] job control: reorganize wait_task_stopped() Message-ID: <20110511192902.GC24245@mtj.dyndns.org> References: <1304869745-1073-1-git-send-email-tj@kernel.org> <1304869745-1073-10-git-send-email-tj@kernel.org> <20110511154854.GB23688@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110511154854.GB23688@redhat.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Wed, May 11, 2011 at 05:48:54PM +0200, Oleg Nesterov wrote: > > It seems that WNOHANG wait correctness has never been guaranteed and > > everybody has been happy with it for very long time. > > Yes, the window is tiny. May be it was never noticed or never > reported because this is hard to diagnose/reproduced. Yeah, most likely. > > As such, > > although this reorganization improves the situation a bit, I don't > > consider this to be a bug fix. > > But it is? > > Can't we push this patch ahead of these changes? I can merge it into > ptrace branch. It doesn't really fix the problem tho. The whole thing is full of holes and I think it would be better to just declare "WNOHANG might fail even when it's not supposed to, retry later" than making the locking heavier there, which could easily be much more relevant regression. Of course, if we can fix it without adding extra locking or too much complexity, it would be nice. Anyways, yeah, sure. I'll resend it as a separate patch. Thanks. -- tejun