From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932130AbWG2NLj (ORCPT ); Sat, 29 Jul 2006 09:11:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751413AbWG2NLj (ORCPT ); Sat, 29 Jul 2006 09:11:39 -0400 Received: from ra.tuxdriver.com ([70.61.120.52]:22282 "EHLO ra.tuxdriver.com") by vger.kernel.org with ESMTP id S1751370AbWG2NLi (ORCPT ); Sat, 29 Jul 2006 09:11:38 -0400 Date: Sat, 29 Jul 2006 09:00:58 -0400 From: Neil Horman To: 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: <20060729130058.GB6669@localhost.localdomain> References: <200607282007.k6SK7DhX009584@ra.tuxdriver.com> <20060729093704.GD26956@flint.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060729093704.GD26956@flint.arm.linux.org.uk> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jul 29, 2006 at 10:37:04AM +0100, Russell King wrote: > 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 think you misread. I want a return code of zero to be valid (and imply success). However, kernel_thread returns an int (not an unsigned int), and there are/were callers who assumed that _any_ non-zero return values were success, including negative return values, which indicate a failure in kernel_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. > I should have been more clear above, point two is meant to indicate that there were callers of kernel_thread which assume a negative return code from kernel_thread meant success. That is what I fixed. Regards Neil > -- > Russell King > Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ > maintainer of: 2.6 Serial core