From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f71.google.com (mail-pa0-f71.google.com [209.85.220.71]) by kanga.kvack.org (Postfix) with ESMTP id CBC9C6B0263 for ; Wed, 12 Oct 2016 17:41:13 -0400 (EDT) Received: by mail-pa0-f71.google.com with SMTP id tz10so56340086pab.3 for ; Wed, 12 Oct 2016 14:41:13 -0700 (PDT) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id t188si7695584pgc.18.2016.10.12.14.41.12 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 12 Oct 2016 14:41:13 -0700 (PDT) Date: Wed, 12 Oct 2016 14:41:12 -0700 From: Andrew Morton Subject: Re: [RFC v2 PATCH] mm/percpu.c: fix panic triggered by BUG_ON() falsely Message-Id: <20161012144112.0494082cf4cbd07609d2405d@linux-foundation.org> In-Reply-To: <57FCF07C.2020103@zoho.com> References: <57FCF07C.2020103@zoho.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: zijun_hu Cc: tj@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, zijun_hu@htc.com, cl@linux.com On Tue, 11 Oct 2016 22:00:28 +0800 zijun_hu wrote: > as shown by pcpu_build_alloc_info(), the number of units within a percpu > group is educed by rounding up the number of CPUs within the group to > @upa boundary, therefore, the number of CPUs isn't equal to the units's > if it isn't aligned to @upa normally. however, pcpu_page_first_chunk() > uses BUG_ON() to assert one number is equal the other roughly, so a panic > is maybe triggered by the BUG_ON() falsely. > > in order to fix this issue, the number of CPUs is rounded up then compared > with units's, the BUG_ON() is replaced by warning and returning error code > as well to keep system alive as much as possible. Under what circumstances is the triggered? In other words, what are the end-user visible effects of the fix? I mean, this is pretty old code (isn't it?) so what are you doing that triggers this? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org