From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752163AbYANPia (ORCPT ); Mon, 14 Jan 2008 10:38:30 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751074AbYANPiX (ORCPT ); Mon, 14 Jan 2008 10:38:23 -0500 Received: from fg-out-1718.google.com ([72.14.220.153]:28074 "EHLO fg-out-1718.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750985AbYANPiW (ORCPT ); Mon, 14 Jan 2008 10:38:22 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version:content-type:content-disposition:in-reply-to:user-agent; b=Ca/37kvPadstYw5Gj6arYc22+ZFNhlk7JQB6Ui6Bhh1A9OkEO4j0a2KQKraVzSZ3y5l8RQc7oPfqu6aBexNkjZvJYfy+qzK+T5IMytBJf4DC59sYh+5Qp/LBcML8h3bC2eU3sOmCsYvgNXj9U+xdHkbxrnCvSL0kqfJ0E82pvVQ= Date: Mon, 14 Jan 2008 18:38:06 +0300 From: Cyrill Gorcunov To: Jiri Slaby Cc: Paul Gortmaker , LKML , Andi Kleen , Alexey Dobriyan Subject: Re: [PATCH] driver: ip27-rtc - convert ioctl to unlocked_ioctl Message-ID: <20080114153806.GA6639@cvg> References: <20080113203223.GA6723@cvg> <478A8131.9050500@gmail.com> <478A82AD.3070904@gmail.com> <478B7C4A.5090903@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <478B7C4A.5090903@gmail.com> User-Agent: Mutt/1.5.16 (2007-06-09) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [Jiri Slaby - Mon, Jan 14, 2008 at 04:14:18PM +0100] > On 01/14/2008 07:38 AM, Cyrill Gorcunov wrote: >> This patch converts ioctl call to unlocked_ioctl form. It's possible >> due to rtl_lock spinlock protection. >> Signed-off-by: Cyrill Gorcunov >> --- >> The patch is *not* tested but the patch does not bring _much_ changes >> so it wouldn't break the compilation procedure. >> If there is problem with attachment - i could send it as inline >> form today evening. > > Yes, please, especially if it is app/octet-stream (base64 encoded > plaintext). Also Cc akpm or somebody who will pick your patch up. > ok >> Andi, Jiri, Alexey the only thing I do complain about - >> is time set/read from several user threads that uses same >> (duplicated) file descriptor. Could there be useless thread >> spins instead of sleep (in case if this unlocked_ioctl were >> protected by mutex)? > > Sorry, what? > Jiri, I mean rtc_open() is protected by spinlock+status from being opened simultaneously by a few processes. *But* lets imagine the following situation - this fd (file descriptor) is opened by one multithreaded application so all threads have an access to this fd. Then one thread reads rtc periodically thru unlocked_ioctl and another thread set new time from time to time. So the question I have - is it possible to get second thread stopped at attemption to get rtc spinlock while another thread is setting the new time? Or this situation never-ever could be? i'm not really familiar with process management in Linux and as result could be wrong. - Cyrill -