From mboxrd@z Thu Jan 1 00:00:00 1970 From: Patrick McHardy Subject: Re: [PATCH 7/9] rhashtable: Per bucket locks & deferred expansion/shrinking Date: Fri, 16 Jan 2015 18:36:26 +0000 Message-ID: <20150116183626.GS30132@acer.localdomain> References: <75db38bc9313a55cf02a8c36a3376c32b691e5d9.1418647641.git.tgraf@suug.ch> <20150116153415.GF30132@acer.localdomain> <20150116155835.GA15052@casper.infradead.org> <20150116160354.GI30132@acer.localdomain> <20150116161530.GC15052@casper.infradead.org> <20150116163202.GJ30132@acer.localdomain> <063D6719AE5E284EB5DD2968C1650D6D1CACADAF@AcuExch.aculab.com> <20150116165302.GE15052@casper.infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: David Laight , "davem@davemloft.net" , "netdev@vger.kernel.org" , "herbert@gondor.apana.org.au" , "paulmck@linux.vnet.ibm.com" , "edumazet@google.com" , "john.r.fastabend@intel.com" , "josh@joshtriplett.org" , "netfilter-devel@vger.kernel.org" To: Thomas Graf Return-path: Received: from stinky.trash.net ([213.144.137.162]:44300 "EHLO stinky.trash.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751720AbbAPSgd (ORCPT ); Fri, 16 Jan 2015 13:36:33 -0500 Content-Disposition: inline In-Reply-To: <20150116165302.GE15052@casper.infradead.org> Sender: netdev-owner@vger.kernel.org List-ID: On 16.01, Thomas Graf wrote: > On 01/16/15 at 04:43pm, David Laight wrote: > > The walker is unlikely to see items that get inserted early in the hash > > table even without a resize. > > I don't follow, you have to explain this statement. > > Walkers which don't want to see duplicates or miss entries should > just take the mutex. Well, we do have a problem with interrupted dumps. As you know once the netlink message buffer is full, we return to userspace and continue dumping during the next read. Expanding obviously changes the order since we rehash from bucket N to N and 2N, so this will indeed cause duplicate (doesn't matter) and missed entries.