From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753456Ab0EOIy6 (ORCPT ); Sat, 15 May 2010 04:54:58 -0400 Received: from straum.hexapodia.org ([207.7.131.186]:34828 "EHLO straum.hexapodia.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753221Ab0EOIy4 (ORCPT ); Sat, 15 May 2010 04:54:56 -0400 Date: Sat, 15 May 2010 01:54:56 -0700 From: Andy Isaacson To: Andrew Morton Cc: Jesse Barnes , linux-kernel@vger.kernel.org, intel-gfx@lists.freedesktop.org, Matthew Garrett Subject: Re: [PATCH 2/2] x86 platform driver: intelligent power sharing driver Message-ID: <20100515085456.GB7125@hexapodia.org> References: <20100510142521.5a705dea@virtuousgeek.org> <20100510142652.12ca0824@virtuousgeek.org> <20100510220046.3f7cd9bf.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100510220046.3f7cd9bf.akpm@linux-foundation.org> X-GPG-Fingerprint: 1914 0645 FD53 C18E EEEF C402 4A69 B1F3 68D2 A63F X-GPG-Key-URL: http://web.hexapodia.org/~adi/gpg.txt X-Domestic-Surveillance: money launder bomb tax evasion 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 Mon, May 10, 2010 at 10:00:46PM -0400, Andrew Morton wrote: > > + int i; > > + u16 avg; > > + > > + for (i = 0; i < IPS_SAMPLE_COUNT; i++) > > + total += (u64)(array[i] * 100); > > Actually, that does work. Somehow the compiler will promote array[i] > to u64 _before_ doing the multiplication. I think. Still, it looks > like a deliberate attempt to trick the compiler into doing a > multiplicative overflow ;) It seems to promote to int, probably due to the implicit type of "100". Aind since array is u16, * 100 can't overflow int. So yes, it's safe, but it does catch the eye as potentially unsafe. > > + cur_seqno = (thm_readl(THM_ITV) & ITV_ME_SEQNO_MASK) >> > > + ITV_ME_SEQNO_SHIFT; > > + if (cur_seqno == last_seqno && > > + time_after(jiffies, seqno_timestamp + HZ)) { > > + dev_warn(&ips->dev->dev, "ME failed to update for more than 1s, likely hung\n"); > > + } else { > > + seqno_timestamp = get_jiffies_64(); > > + last_seqno = cur_seqno; > > + } > > + > > + last_msecs = jiffies_to_msecs(jiffies); Once it triggers, this will print the "likely hung" message every second until the end of time, won't it? -andy