 Home |
Products |
Support |
Community |
News |
xen-devel
Re: [Xen-devel] regression from c/s 22071:c5aed2e049bc (ept: Put locks a
| To: | Tim Deegan <Tim.Deegan@xxxxxxxxxx> |
|---|---|
| Subject: | Re: [Xen-devel] regression from c/s 22071:c5aed2e049bc (ept: Put locks around ept_get_entry) ? |
| From: | George Dunlap <George.Dunlap@xxxxxxxxxxxxx> |
| Date: | Mon, 20 Dec 2010 16:24:23 +0000 |
| Cc: | "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Keir Fraser <keir@xxxxxxx>, Jan Beulich <JBeulich@xxxxxxxxxx> |
| Delivery-date: | Mon, 20 Dec 2010 08:39:32 -0800 |
| Dkim-signature: | v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:sender:received :in-reply-to:references:date:x-google-sender-auth:message-id:subject :from:to:cc:content-type:content-transfer-encoding; bh=Ig/X02xbXxRB59IAikXOVV+TYpUBntNYlUX6WHeoEww=; b=t3yXW4BP705wpAm1cOKqU5dHgMK6sb9MAywn1L9e/b8rnHB1oQ4AlJadJZeO4ournY INTOD58P2AjeonimctKLIvyxV9N/8uMMos5zglnRu5aNtwgcXmLKtqkf9UFZJ7pj7w1J eKcZmd423CBQdAeM9Uxq1GRJydSDEI/w0DsCA= |
| Domainkey-signature: | a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type :content-transfer-encoding; b=iHv34Mbh4ptxaK3DAr/FslrtNzr9XmIuMuZUyu6twzny2gwfbQuG1E4sX1bUMhB3lC gGEi/oLfw4ZqAnTOUlQyluKTxFMwDPqRjJVxlsu6WbuPEwOh2nJMjKuVn1JWP2Bl5iH9 EqWZ47Lp3kGdFf8KFxiczsUMnZKzRWDQptDlI= |
| Envelope-to: | www-data@xxxxxxxxxxxxxxxxxxx |
| In-reply-to: | <20101217111548.GQ9912@xxxxxxxxxxxxxxxxxxxxxxx> |
| List-help: | <mailto:xen-devel-request@lists.xensource.com?subject=help> |
| List-id: | Xen developer discussion <xen-devel.lists.xensource.com> |
| List-post: | <mailto:xen-devel@lists.xensource.com> |
| List-subscribe: | <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe> |
| List-unsubscribe: | <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe> |
| References: | <C92FF6CF.295FC%keir@xxxxxxx> <C930286C.29670%keir@xxxxxxx> <20101217111548.GQ9912@xxxxxxxxxxxxxxxxxxxxxxx> |
| Sender: | xen-devel-bounces@xxxxxxxxxxxxxxxxxxx |
Sorry for the delay in responding; I caught a bad cold, and was in no state to comment on making lockless races benign. :-) On Fri, Dec 17, 2010 at 11:15 AM, Tim Deegan <Tim.Deegan@xxxxxxxxxx> wrote: > George, I think the underlying logic is still racy - the > check-and-populate function is checking a pointer that was found outside > the lock. It needs to start again from the beginning to be safe, which > probably means just dropping the "check" part and letting the > p2m_pod_demand_populate handle lost races. Also, why doesn't > ept_get_entry use a single read at the lowest level? My main goal when I wrote this patch was to fix a bug our testing found that was going to slip a release, and then move on to other pressing issues. So I'm sure there's more raciness to clean up in here that just isn't triggered generally. I think you're right, dropping the check and doing it in p2m_pod_demand_populate() is probably the Right Thing to do. I've got that stack of patches to deal with in January, I'll work on it then. -George Dunlap _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel |
| Previous by Date: | [Xen-devel] [PATCH 04/12] Nested Virtualization: core, Christoph Egger |
|---|---|
| Next by Date: | Re: [Xen-devel] [PATCH 13/13] Nested Virtualization: hap-on-hap, Christoph Egger |
| Previous by Thread: | Re: [Xen-devel] regression from c/s 22071:c5aed2e049bc (ept: Put locks around ept_get_entry) ?, Tim Deegan |
| Next by Thread: | Re: [Xen-devel] regression from c/s 22071:c5aed2e049bc (ept: Put locks around ept_get_entry) ?, Olaf Hering |
| Indexes: | [Date] [Thread] [Top] [All Lists] |
