From: Jeff Layton Subject: Re: [PATCH 1/4] SUNRPC: spin svc_rqst initialization to its own function Date: Fri, 18 Jan 2008 16:48:44 -0500 Message-ID: <20080118164844.7f91d6ff@tleilax.poochiereds.net> References: <1200319518-22422-1-git-send-email-jlayton@redhat.com> <1200319518-22422-2-git-send-email-jlayton@redhat.com> <20080118205943.GL15158@fieldses.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Cc: neilb@suse.de, linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org To: "J. Bruce Fields" Return-path: Received: from mx1.redhat.com ([66.187.233.31]:44192 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761415AbYARVst (ORCPT ); Fri, 18 Jan 2008 16:48:49 -0500 In-Reply-To: <20080118205943.GL15158@fieldses.org> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Fri, 18 Jan 2008 15:59:43 -0500 "J. Bruce Fields" wrote: > On Mon, Jan 14, 2008 at 09:05:15AM -0500, Jeff Layton wrote: > > Move the initialzation in __svc_create_thread that happens prior to > > thread creation to a new function. Export the function to allow > > services to have better control over the svc_rqst structs. > > > > Also rearrange the rqstp initialization to prevent NULL pointer > > dereferences in svc_exit_thread in case allocations fail. > > Those NULL dereferences are from the > > list_del(&rqstp->rq_all); > > ? OK, make sense. Thanks! > > --b. > Sorry, I didn't explain that well... This was the problem that Neil pointed out with the existing code. If the rqstp kzalloc succeeds, but the later kmallocs in __svc_create_thread fail, we goto here: out_thread: svc_exit_thread(rqstp); svc_exit_thread does this: struct svc_pool *pool = rqstp->rq_pool; ...and then later: spin_lock_bh(&pool->sp_lock); ...but rq_pool is set after the kmallocs, so if they fail rq_pool will be NULL, and we'll oops in that spin_lock_bh(). The fix is to move the kmallocs closer to the bottom in the new svc_prepare_thread function. Thanks, -- Jeff Layton