From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756641AbdKNUlq (ORCPT ); Tue, 14 Nov 2017 15:41:46 -0500 Received: from bombadil.infradead.org ([65.50.211.133]:49268 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752528AbdKNUlj (ORCPT ); Tue, 14 Nov 2017 15:41:39 -0500 Date: Tue, 14 Nov 2017 12:41:35 -0800 From: Matthew Wilcox To: luca abeni , Peter Zijlstra , Daniel Bristot de Oliveira , Ingo Molnar Cc: linux-kernel@vger.kernel.org Subject: New sparse warnings from sched.h Message-ID: <20171114204135.GA23685@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.8.3 (2017-05-23) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org commit 799ba82de01e7543f6b2042e1a739f3a20255f23 Author: luca abeni Date: Thu Sep 7 12:09:31 2017 +0200 sched/deadline: Use C bitfields for the state flags Ask the compiler to use a single bit for storing true / false values, instead of wasting the size of a whole int value. Tested with gcc 5.4.0 on x86_64, and the compiler produces the expected Assembly (similar to the Assembly code generated when explicitly accessing the bits with bitmasks, "&" and "|"). produces four warnings from sparse for every file which includes sched.h: ./include/linux/sched.h:476:62: error: dubious one-bit signed bitfield ./include/linux/sched.h:477:62: error: dubious one-bit signed bitfield ./include/linux/sched.h:478:62: error: dubious one-bit signed bitfield ./include/linux/sched.h:479:62: error: dubious one-bit signed bitfield This seems like the trivial fix (untested): diff --git a/include/linux/sched.h b/include/linux/sched.h index a5dc7c98b0a2..21991d668d35 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -473,10 +473,10 @@ struct sched_dl_entity { * conditions between the inactive timer handler and the wakeup * code. */ - int dl_throttled : 1; - int dl_boosted : 1; - int dl_yielded : 1; - int dl_non_contending : 1; + unsigned int dl_throttled : 1; + unsigned int dl_boosted : 1; + unsigned int dl_yielded : 1; + unsigned int dl_non_contending : 1; /* * Bandwidth enforcement timer. Each -deadline task has its