From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CA8991DD3B7 for ; Wed, 7 Aug 2024 10:39:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723027160; cv=none; b=kENRiRUxudW2mFBSIkasgaZQkQya8UXMHWbB9Dz5FNg4J4RGc7jYKV8OfsV2I61HJwXObdnoTENQovDf9atZfJt+H6c62sNv0FWTacpTf5bobKfkoxHAERROTHfTMAJsm3TG0mrLXu8ds4AMlO4c7ZCOIJWsgQWjQoexMDDj7oE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723027160; c=relaxed/simple; bh=ZKitO714lu9CKNW4DLq2oKxNA9CXFV/1xGHNdbkyfBk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=RHjYEkCWlHlU/p18t9vcnO5m6H2+2mus57aEohfcLqJxffysi89yH5seFd8VEyPdIRkkeXzPtrp0ehS3ejS+g7XEFESpF0R8wDlfT0wFmk7T+x6Lba/GneEYsOXWg4k9a6oxoRWLZMLn/F6FbQEMAovE4egWG6ph3cAlmcDlkDo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=MSKJY/J4; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="MSKJY/J4" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=SUCekAmG9HzEGJjlLQM1iQQQrs2gzu8lpz8xzqLGNiM=; b=MSKJY/J4dDdsGS2EwjC6t/zEXa SeehV8ff6jFgge9McGDZpzwLuDanf7w2LXRl4IlSw/KiJ7Vmf5eaGN1lRyc9IimmtOovgDeocKWO8 ixFrIm7r/QR+dLRKzx13TGMgGzDStXUXP47Xjsl47I4V4b7Ghpt3P7oYMzi6M8rAi6ukw2NUspe9w T8SCIna2vd/OgP6ml6PSb2LKs3kOg1pIYk0HWopoWGewvirjsRU9DngAeRVMAbkQNNYM77n05op+G +RXn3yy6mSgr4if9ZqACRgbfv4I7U8AWEljxoYx16sIkXjMeQLZ8sWq4j4Jivm09ZqR/oYaT+sElP ka2QdLBg==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.97.1 #2 (Red Hat Linux)) id 1sbe4N-00000006bd7-3Zyn; Wed, 07 Aug 2024 10:39:04 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 7915230033D; Wed, 7 Aug 2024 12:39:02 +0200 (CEST) Date: Wed, 7 Aug 2024 12:39:02 +0200 From: Peter Zijlstra To: Vincent Guittot Cc: Arnd Bergmann , Ingo Molnar , Juri Lelli , Arnd Bergmann , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , linux-kernel@vger.kernel.org, Dan Carpenter Subject: Re: [PATCH] sched/fair: avoid integer overflow warning for fair_server_period_max; Message-ID: <20240807103902.GU39708@noisy.programming.kicks-ass.net> References: <20240807080032.2302853-1-arnd@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Wed, Aug 07, 2024 at 12:00:35PM +0200, Vincent Guittot wrote: > Hi Arnd > > On Wed, 7 Aug 2024 at 10:00, Arnd Bergmann wrote: > > > > From: Arnd Bergmann > > > > The clalculation of fair_server_period_max includes an integer overflow: > > > > In file included from kernel/sched/build_utility.c:72: > > kernel/sched/debug.c:341:57: error: integer overflow in expression of type 'long int' results in '-100663296' [-Werror=overflow] > > 341 | static unsigned long fair_server_period_max = (1 << 22) * NSEC_PER_USEC; /* ~4 seconds */ > > > > Avoids this by using an unsigned constant to start with. > > Dan sent something similar > https://lore.kernel.org/lkml/a936b991-e464-4bdf-94ab-08e25d364986@stanley.mountain/ Right, tglx also pointed me at a report for this. Let me go queue Dan's patch. > > > > Fixes: d741f297bcea ("sched/fair: Fair server interface") > > Signed-off-by: Arnd Bergmann > > --- > > kernel/sched/debug.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c > > index 0148bc65d39c..242e7f264a0b 100644 > > --- a/kernel/sched/debug.c > > +++ b/kernel/sched/debug.c > > @@ -338,7 +338,7 @@ enum dl_param { > > DL_PERIOD, > > }; > > > > -static unsigned long fair_server_period_max = (1 << 22) * NSEC_PER_USEC; /* ~4 seconds */ > > +static unsigned long fair_server_period_max = (1u << 22) * NSEC_PER_USEC; /* ~4 seconds */ > > static unsigned long fair_server_period_min = (100) * NSEC_PER_USEC; /* 100 us */ > > > > static ssize_t sched_fair_server_write(struct file *filp, const char __user *ubuf, > > -- > > 2.39.2 > >