From owner-svn-src-head@freebsd.org Fri Aug 4 13:47:52 2017 Return-Path: Delivered-To: svn-src-head@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 35024DAB9EE; Fri, 4 Aug 2017 13:47:52 +0000 (UTC) (envelope-from cse.cem@gmail.com) Received: from mail-pf0-f195.google.com (mail-pf0-f195.google.com [209.85.192.195]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 06E65690CF; Fri, 4 Aug 2017 13:47:51 +0000 (UTC) (envelope-from cse.cem@gmail.com) Received: by mail-pf0-f195.google.com with SMTP id h75so1936046pfh.5; Fri, 04 Aug 2017 06:47:51 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:reply-to:in-reply-to:references :from:date:message-id:subject:to:cc; bh=+cUnZPtf8F5i7i1U3WidRZhzJa9Arua31+BW4wA4yDE=; b=Vyd70VTDDJspAOc/+CNO8uYvd9En9mvxFTstQ381ytjyQcNjKiJgsYTgaDTlkb3gmu VFQiY0ThdrVmBy/xYFD6JAAkXmGUIl/sUVWUPD5hmdQZDHCAB4yiqrWV8ymurDGPUMra mPZ1XSs5qiEsoNqOI6UuE3y3/XeZU4N9CvJ9ljdGnRC3jIN8423fBsF605wjW1Z306rY YhYuw3Gh+jm5BFZHhsXQRfeKbD+hLR0nGbhfqUr4ExGz59DpR5gmpyU/hBcadrgpcYpF YhSAye2XTIJP7r8I1jz9UdYkV/1d34g2cBQwUB2+rNk+q7ZrBNwR6vvQaBHOrgHRUZZX b9gw== X-Gm-Message-State: AIVw112nuBnHWQf9ltib+jzgtMHvkmR79ms0eObf2iFhcksv51KJvn1n HRGsFx9W4Gg0Sye8/8c= X-Received: by 10.84.167.2 with SMTP id c2mr2848681plb.366.1501854470648; Fri, 04 Aug 2017 06:47:50 -0700 (PDT) Received: from mail-pg0-f43.google.com (mail-pg0-f43.google.com. [74.125.83.43]) by smtp.gmail.com with ESMTPSA id 80sm3372081pfr.90.2017.08.04.06.47.50 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 04 Aug 2017 06:47:50 -0700 (PDT) Received: by mail-pg0-f43.google.com with SMTP id l64so8236676pge.5; Fri, 04 Aug 2017 06:47:50 -0700 (PDT) X-Received: by 10.101.90.7 with SMTP id y7mr2363885pgs.29.1501854470200; Fri, 04 Aug 2017 06:47:50 -0700 (PDT) MIME-Version: 1.0 Reply-To: cem@freebsd.org Received: by 10.100.169.8 with HTTP; Fri, 4 Aug 2017 06:47:49 -0700 (PDT) In-Reply-To: <0100015dabf99099-b39e4e26-cd45-4099-aa91-49820f55aacd-000000@email.amazonses.com> References: <201708030918.v739IPVY034866@repo.freebsd.org> <0100015dabf99099-b39e4e26-cd45-4099-aa91-49820f55aacd-000000@email.amazonses.com> From: Conrad Meyer Date: Fri, 4 Aug 2017 06:47:49 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: svn commit: r321985 - head/sys/ofed/drivers/infiniband/core To: Colin Percival Cc: Hans Petter Selasky , src-committers , svn-src-all@freebsd.org, svn-src-head@freebsd.org Content-Type: text/plain; charset="UTF-8" X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 04 Aug 2017 13:47:52 -0000 On Thu, Aug 3, 2017 at 11:40 PM, Colin Percival wrote: > On 08/03/17 23:28, Hans Petter Selasky wrote: >> On 08/03/17 16:37, Conrad Meyer wrote: >>> Is it not important that the subtraction and result are evaluated >>> without truncation? >> >> ticks is a circular counter. Assuming time = 0 and jiffies = -1U, then "delay" >> becomes a very large negative value, because long is used, and the delay <= 0 >> check, is no longer working like expected. >> >> Casting to "int" or truncating is the right thing to do in this case. > > Signed integer overflow is undefined. Using 'int' is liable to cause problems > after 2^32 ticks. It is undefined in C, but defined in practice with -fwrapv, which the kernel relies upon already. Best, Conrad