Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752847AbbDGJbv (ORCPT ); Tue, 7 Apr 2015 05:31:51 -0400 Received: from mail-wg0-f50.google.com ([74.125.82.50]:33137 "EHLO mail-wg0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751033AbbDGJbu (ORCPT ); Tue, 7 Apr 2015 05:31:50 -0400 Date: Tue, 7 Apr 2015 11:31:45 +0200 From: Ingo Molnar To: Linus Torvalds Cc: Sasha Levin , LKML , Rusty Russell , Dave Jones , Michal Hocko , Borislav Petkov , the arch/x86 maintainers Subject: Re: Hang on large copy_from_user with PREEMPT_NONE Message-ID: <20150407093145.GA10348@gmail.com> References: <552204B8.40605@oracle.com> <5522D9A8.5080104@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 873 Lines: 24 * Linus Torvalds wrote: > On Mon, Apr 6, 2015 at 12:08 PM, Sasha Levin wrote: > > > > Your patch just makes it hang in memset instead: > > So it's certainly a big memset (2GB or so: original count in RDX: > 0x7e777000, and "%rcx << 6" is bytes left, so it has done about 85% > of it), which is certainly going to be slow, but it shouldn't > *hang*. [...] Would be nice to see the actual kernel .config, as there's a few debug features that can slow things down significantly, such as CONFIG_KMEMCHECK=y or in some cases CONFIG_DEBUG_PAGEALLOC=y. Thanks, Ingo -- 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/