From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1422707AbWG2JhS (ORCPT ); Sat, 29 Jul 2006 05:37:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1422708AbWG2JhS (ORCPT ); Sat, 29 Jul 2006 05:37:18 -0400 Received: from caramon.arm.linux.org.uk ([217.147.92.249]:50705 "EHLO caramon.arm.linux.org.uk") by vger.kernel.org with ESMTP id S1422707AbWG2JhL (ORCPT ); Sat, 29 Jul 2006 05:37:11 -0400 Date: Sat, 29 Jul 2006 10:37:04 +0100 From: Russell King To: nhorman@tuxdriver.com Cc: kernel-janitors@osdl.org, linux-kernel@vger.kernel.org, schwidefsky@de.ibm.com Subject: Re: [KJ] audit return code handling for kernel_thread [2/11] Message-ID: <20060729093704.GD26956@flint.arm.linux.org.uk> Mail-Followup-To: nhorman@tuxdriver.com, kernel-janitors@osdl.org, linux-kernel@vger.kernel.org, schwidefsky@de.ibm.com References: <200607282007.k6SK7DhX009584@ra.tuxdriver.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200607282007.k6SK7DhX009584@ra.tuxdriver.com> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 28, 2006 at 04:07:13PM -0400, nhorman@tuxdriver.com wrote: > Audit/Cleanup of kernel_thread calls, specifically checking of return codes. > Problems seemed to fall into 3 main categories: > > 1) callers of kernel_thread were inconsistent about meaning of a zero return > code. Some callers considered a zero return code to mean success, others took > it to mean failure. a zero return code, while not actually possible in the > current implementation, should be considered a success (pid 0 is/should be > valid). fixed all callers to treat zero return as success > > 2) caller of kernel_thread saved return code of kernel_thread for later use > without ever checking its value. Callers who did this tended to assume a > non-zero return was success, and would often wait for a completion queue to be > woken up, implying that an error (negative return code) from kernel_thread could > lead to deadlock. Repaired by checking return code at call time, and setting > saved return code to zero in the event of an error. This is inconsistent with your assertion that pid 0 "is/should be valid" above. If you want '0' to mean "not valid" then it's not a valid return value from kernel_thread() (and arguably that's true, since pid 0 is permanently allocated to the idle thread.) I don't particularly care whether you decide to that returning pid 0 from kernel_thread is valid or not, just that your two points above are at least consistent with each other. -- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: 2.6 Serial core