Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Mon, 15 Apr 2019 14:46:17 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Cheng Jian <cj.chengjian@huawei.com>
Cc:     huawei.libin@huawei.com, xiexiuqi@huawei.com,
        yangyingliang@huawei.com, mingo@redhat.com,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] sched/fair: Use 'unsigned long' for
 group_shares,group_runnable
Message-ID: <20190415124617.GP11158@hirez.programming.kicks-ass.net>
References: <20190413033234.30002-1-cj.chengjian@huawei.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20190413033234.30002-1-cj.chengjian@huawei.com>
User-Agent: Mutt/1.10.1 (2018-07-13)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Sat, Apr 13, 2019 at 03:32:34AM +0000, Cheng Jian wrote:
> group_share and group_runnable are tracked as 'unsigned long',
> however some functions using them as 'long' which is ultimately
> assigned back to 'unsigned long' variables in reweight_entity.
> 
> Since there is not scope on using a different and signed type,
> this change improves code consistency and avoids further type
> conversions. More important, to prevent undefined behavior
> caused by overflow.

There is no undefined behaviour due to overflow. UBSAN is broken,
upgrade to GCC8 or later.