From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753185AbbCWTM6 (ORCPT ); Mon, 23 Mar 2015 15:12:58 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59651 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752573AbbCWTMz (ORCPT ); Mon, 23 Mar 2015 15:12:55 -0400 Date: Mon, 23 Mar 2015 20:10:55 +0100 From: Oleg Nesterov To: Davidlohr Bueso Cc: Konstantin Khlebnikov , linux-mm@kvack.org, Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: fix lockdep build in rcu-protected get_mm_exe_file() Message-ID: <20150323191055.GA10212@redhat.com> References: <20150320144715.24899.24547.stgit@buzz> <1427134273.2412.12.camel@stgolabs.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1427134273.2412.12.camel@stgolabs.net> 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 On 03/23, Davidlohr Bueso wrote: > > void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) > { > struct file *old_exe_file = rcu_dereference_protected(mm->exe_file, > - !atomic_read(&mm->mm_users) || current->in_execve || > - lock_is_held(&mm->mmap_sem)); > + !atomic_read(&mm->mm_users) || current->in_execve); Thanks, looks correct at first glance... But can't we remove the ->in_execve check above? and check atomic_read(&mm->mm_users) <= 1 instead. OK, this is subjective, I won't insist. Just current->in_execve looks a bit confusing, it means "I swear, the caller is flush_old_exec() and this mm is actualy bprm->mm". "atomic_read(&mm->mm_users) <= 1" looks a bit more "safe". But again, I won't insist. Oleg.