From mboxrd@z Thu Jan 1 00:00:00 1970 From: Major Hayden Subject: Re: Xen BUG at page_alloc.c:1738 (Xen 4.5) Date: Wed, 20 May 2015 11:52:23 -0500 Message-ID: <555CBBC7.2070201@mhtx.net> References: <555B7BB8.90909@mhtx.net> <555C80EA020000780007C12D@mail.emea.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <555C80EA020000780007C12D@mail.emea.novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Jan Beulich Cc: xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org On 05/20/2015 05:41 AM, Jan Beulich wrote: > Considering that no-one else is seeing this - is this perhaps connected > to you building Xen with pre-release gcc 5.0.1? This is also because in > order for the above to indeed occur, mmio_ro_do_page_fault()'s > put_page() would need to drop the last reference of a page, yet > page_get_owner_and_reference() doesn't obtain a reference when > a page is unallocated (and hence unowned), i.e. normally a page > would have a refcount of at least 2 here. Hence this would be > possible only due to a race, but the exact same race to be observed > on different hardware _and_ under an emulator is extremely unlikely. That could be a possibility. There is one Fedora patch[1] to fix a GCC 5 compile error but that's probably unrelated to the crash. I'm still hunting around to see what I can figure out. [1] http://pkgs.fedoraproject.org/cgit/xen.git/tree/?h=f22 -- Major Hayden