From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 16 May 2002 17:40:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 16 May 2002 17:40:54 -0400 Received: from scfdns02.sc.intel.com ([143.183.152.26]:9688 "EHLO crotus.sc.intel.com") by vger.kernel.org with ESMTP id ; Thu, 16 May 2002 17:40:53 -0400 Message-Id: <200205162140.g4GLelw01400@unix-os.sc.intel.com> Content-Type: text/plain; charset=US-ASCII From: Mark Gross Reply-To: mgross@unix-os.sc.intel.com Organization: SSG Intel To: Robert Love , Alan Cox Subject: Re: PATCH Multithreaded core dump support for the 2.5.14 (and 15) kernel. Date: Thu, 16 May 2002 14:40:24 -0400 X-Mailer: KMail [version 1.3.1] Cc: Daniel Jacobowitz , Andi Kleen , linux-kernel@vger.kernel.org In-Reply-To: <1021584279.914.4.camel@sinai> MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thursday 16 May 2002 05:24 pm, Robert Love wrote: > On Thu, 2002-05-16 at 14:32, Alan Cox wrote: > > > For this to happen that semaphore would have to held across > > > schedule()'s. The ONLY place I've seen that in the kernel is > > > set_CPUs_allowed + migration_thread. > > > > The 2.5 kernel is pre-emptible. > > Indeed :) > > But there is plenty of places in the kernel - sans preemption - where we > sleep while holding a semaphore. Was that the original question? If > so, set_cpus_allowed by be one of the few _explicit_ places but we > implicitly sleep holding a semaphore all over. Heck, we use them for > user-space synchronization. > > Robert Love > The original question was: Couldn't the TCore patch deadlock in elf_core_dump on a semiphore held by a sleeping process that gets placed onto the phantom runque? So far I can't tell the problem is real or not, but I'm worried :( I haven't hit any such deadlocks in my stress testing, such as it is. In my review of the code I don't see any obviouse problems dispite the fact that the mmap_sem is explicitly grabbed by elf_core_dump. --mgross