From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f53.google.com (mail-pa0-f53.google.com [209.85.220.53]) by kanga.kvack.org (Postfix) with ESMTP id 121FD6B0035 for ; Fri, 27 Dec 2013 17:26:07 -0500 (EST) Received: by mail-pa0-f53.google.com with SMTP id hz1so9663054pad.40 for ; Fri, 27 Dec 2013 14:26:07 -0800 (PST) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTP id bc2si25532656pad.158.2013.12.27.14.26.06 for ; Fri, 27 Dec 2013 14:26:06 -0800 (PST) Date: Fri, 27 Dec 2013 14:26:05 -0800 From: Andrew Morton Subject: Re: [PATCH] mm: dump page when hitting a VM_BUG_ON using VM_BUG_ON_PAGE Message-Id: <20131227142605.5830bf0e4b9bb007c2916dfc@linux-foundation.org> In-Reply-To: <52BDFD00.7020909@oracle.com> References: <1388114452-30769-1-git-send-email-sasha.levin@oracle.com> <20131227103847.GA19453@node.dhcp.inet.fi> <52BDFD00.7020909@oracle.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: Sasha Levin Cc: "Kirill A. Shutemov" , linux-mm@kvack.org, linux-kernel@vger.kernel.org On Fri, 27 Dec 2013 17:19:44 -0500 Sasha Levin wrote: > On 12/27/2013 05:38 AM, Kirill A. Shutemov wrote: > > On Thu, Dec 26, 2013 at 10:20:52PM -0500, Sasha Levin wrote: > >> Most of the VM_BUG_ON assertions are performed on a page. Usually, when > >> one of these assertions fails we'll get a BUG_ON with a call stack and > >> the registers. > >> > >> I've recently noticed based on the requests to add a small piece of code > >> that dumps the page to various VM_BUG_ON sites that the page dump is quite > >> useful to people debugging issues in mm. > >> > >> This patch adds a VM_BUG_ON_PAGE(cond, page) which beyond doing what > >> VM_BUG_ON() does, also dumps the page before executing the actual BUG_ON. > >> > >> Signed-off-by: Sasha Levin > > > > I like the idea. One thing I've noticed you have a lot of page flag based > > asserts, like: > > > > VM_BUG_ON_PAGE(PageLRU(page), page); > > VM_BUG_ON_PAGE(!PageLocked(page), page); > > > > What about adding per-page-flag assert macros, like: > > > > PageNotLRU_assert(page); > > PageLocked_assert(page); > > > > ? This way we will always dump right page on bug. > > > > Sure, sounds good. > > I'll send another patch on top of this one. I think I prefer the patch as-is. To do what Kirill suggests we'd have to add a heck of a lot more macros and they add little value. And the suggested names of those macros aren't very good - there's nothing in "PageNotLRU_assert" which tells the reader that this code is conditional on CONFIG_DEBUG_VM, which is a somewhat important thing. -- 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