Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752845Ab3CPV0K (ORCPT ); Sat, 16 Mar 2013 17:26:10 -0400 Received: from mx1.redhat.com ([209.132.183.28]:10356 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751339Ab3CPV0H (ORCPT ); Sat, 16 Mar 2013 17:26:07 -0400 Date: Sat, 16 Mar 2013 22:23:51 +0100 From: Oleg Nesterov To: Andi Kleen Cc: Andrew Morton , Linus Torvalds , Lucas De Marchi , Benjamin Herrenschmidt , Linux Kernel Mailing List , Paul Mackerras , david@gibson.dropbear.id.au, Kees Cook , Serge Hallyn , "Rafael J. Wysocki" , Feng Hong , Lucas De Marchi Subject: Re: [PATCH 0/2] finx argv_split() vs sysctl race Message-ID: <20130316212351.GA21190@redhat.com> References: <20130312203514.GA23488@redhat.com> <20130313174641.GA28083@redhat.com> <20130313174705.GB28083@redhat.com> <20130314152819.7fb1242b493e8bad2d34671b@linux-foundation.org> <20130315163916.GA31995@redhat.com> <20130316202327.GA18613@redhat.com> <20130316203221.GT11268@two.firstfloor.org> <20130316204539.GA19462@redhat.com> <20130316205634.GU11268@two.firstfloor.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130316205634.GU11268@two.firstfloor.org> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1125 Lines: 36 On 03/16, Andi Kleen wrote: > > > Perhaps rcu can be better, although a global rwsem looks simpler, > > I dunno. > > It's a general problem with lots of sysctls. > > > > But argv_split() or its usage should be changed anyway, and GFP_KERNEL > > won't work under rcu_read_lock(). > > rcu strings has a helper function to copy the string for sleepy cases. Then you need to pre-allocate, take rcu_read_lock(), copy, and check that it actually fits the pre-allocated buffer. Not sure why the simple rwsem is worse. But I won't argue in any case > > To me 1/2 looks as a simplification anyway, but I won't argue if we > > decide to add rcu/locking and avoid this patch. > > Ok I'll revisit. OK, but do you agree with 1/2? Once again, this is subjective of course but imho this patch could be considered as a cleanup/microoptimization, and it won't affect the rcu changes. Oleg. -- 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/