From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from fg-out-1718.google.com ([72.14.220.152]:31732 "EHLO fg-out-1718.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757264AbZINVuu (ORCPT ); Mon, 14 Sep 2009 17:50:50 -0400 Message-ID: <4AAEBABA.9060108@gmail.com> Date: Mon, 14 Sep 2009 23:50:50 +0200 From: Jiri Slaby MIME-Version: 1.0 To: Andreas Mohr CC: Guennadi Liakhovetski , Mauro Carvalho Chehab , Luca Risolia , linux-media@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: V4L2 drivers: potentially dangerous and inefficient msecs_to_jiffies() calculation References: <20090914210741.GA16799@rhlx01.hs-esslingen.de> <4AAEB6F0.4080706@gmail.com> <20090914213933.GA5468@rhlx01.hs-esslingen.de> In-Reply-To: <20090914213933.GA5468@rhlx01.hs-esslingen.de> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: On 09/14/2009 11:39 PM, Andreas Mohr wrote: > On Mon, Sep 14, 2009 at 11:34:40PM +0200, Jiri Slaby wrote: >> On 09/14/2009 11:07 PM, Andreas Mohr wrote: >>> msecs_to_jiffies(1) is quite a bit too boldly assuming >>> that all of the msecs_to_jiffies(x) implementation branches >>> always round up. >> >> They do, don't they? > > I'd hope so, but a slight risk remains, you never know, > especially with 4+ or so variants... A potential problem here is rather that it may wait longer due to returning 1 jiffie. It's then timeout * 1000 * 1. On 250HZ system it makes a difference of multiple of 4. Don't think it's a real issue in those drivers at all, but it's worth fixing. Care to post a patch?