From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Jan Beulich" Subject: Re: regression from c/s 22071:c5aed2e049bc (ept: Put locks around ept_get_entry) ? Date: Thu, 16 Dec 2010 15:51:36 +0000 Message-ID: <4D0A439802000078000286FC@vpn.id2.novell.com> References: <4D073B3A0200007800027BDF@vpn.id2.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: Content-Disposition: inline List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: George Dunlap Cc: Christoph Egger , "xen-devel@lists.xensource.com" List-Id: xen-devel@lists.xenproject.org >>> On 14.12.10 at 11:47, George Dunlap = wrote: > Attached is a ported patch that removes locking in ept_get_entry(), > and implements access-once semantics for reading and writing. This > solves the original problem (a race between reading and writing the > table) without causing deadlocks. I haven't had a chance to test it > -- can you give it a spin? I think this is missing some barrier() instances (or volatile qualifiers). Without them, I don't think there's a guarantee that the single memory access in the source won't be converted to multiple ones at the compiler's discretion. Jan