From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753626Ab2DMVFz (ORCPT ); Fri, 13 Apr 2012 17:05:55 -0400 Received: from mail-pz0-f52.google.com ([209.85.210.52]:55928 "EHLO mail-pz0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751080Ab2DMVFx (ORCPT ); Fri, 13 Apr 2012 17:05:53 -0400 Date: Fri, 13 Apr 2012 14:05:48 -0700 From: Tejun Heo To: Vivek Goyal Cc: axboe@kernel.dk, ctalbott@google.com, rni@google.com, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, containers@lists.linux-foundation.org Subject: Re: [PATCH 07/11] blkcg: make request_queue bypassing on allocation Message-ID: <20120413210548.GG12233@google.com> References: <1334347895-6268-1-git-send-email-tj@kernel.org> <1334347895-6268-8-git-send-email-tj@kernel.org> <20120413203205.GI26383@redhat.com> <20120413203726.GE12233@google.com> <20120413204446.GK26383@redhat.com> <20120413204710.GF12233@google.com> <20120413205501.GL26383@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120413205501.GL26383@redhat.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 13, 2012 at 04:55:01PM -0400, Vivek Goyal wrote: > But neither seems to be the case here. So to make sure that blkg_lookup() > under rcu will see the updated value of queue flag (bypass), are we > relying on the fact that caller should see the DEAD flag and not go > ahead with blkg_lookup()? If yes, atleast it is not obivious. We're relying on the fact that it doesn't matter anymore because all blkgs will be shoot down in queue cleanup path which goes through rcu free, which is different from deactivating individual policies. It indeed is subtle. Umm... this is starting to get ridiculous. Why the hell was megaraid messing with so many queues anyways? Thanks. -- tejun From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH 07/11] blkcg: make request_queue bypassing on allocation Date: Fri, 13 Apr 2012 14:05:48 -0700 Message-ID: <20120413210548.GG12233@google.com> References: <1334347895-6268-1-git-send-email-tj@kernel.org> <1334347895-6268-8-git-send-email-tj@kernel.org> <20120413203205.GI26383@redhat.com> <20120413203726.GE12233@google.com> <20120413204446.GK26383@redhat.com> <20120413204710.GF12233@google.com> <20120413205501.GL26383@redhat.com> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; bh=CiDcQtChNzN5tKA/BLDWwL5DrNxXK0ajdTaih18D4L8=; b=uudo8T2FpaCBuCUMcW0Rj0oEW8J1Qza++6GkE+LneI5gWg2Cq/FZfsK/05OZ4oslq9 E6Ydbd+hdHd/h08VwUizeoPYYiktTQIQ6SjxlC1Df/rnJS6G2l2f39qRyUgTy4UD7Dr3 tM0oJnV0q6tSmk1CEivkKwyTuSy5ShdVCX8xdsXATue5D5EINypLr861CZcxk7Qu+xsW LCP19AzYeIsOBPCuKulyvIuJ6nO6jKJAusvXFWcY5wmsVq5XUdOkJkJnTbIsjeWvU+ce 6a9PAqw3Wx1hQSenGUM0BH7oCIb119IPNI4kvpmehnOxW3EfhPjQM+1sLsFNy/qPdFpL I27w== Content-Disposition: inline In-Reply-To: <20120413205501.GL26383-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Vivek Goyal Cc: axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org, ctalbott-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, rni-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org On Fri, Apr 13, 2012 at 04:55:01PM -0400, Vivek Goyal wrote: > But neither seems to be the case here. So to make sure that blkg_lookup() > under rcu will see the updated value of queue flag (bypass), are we > relying on the fact that caller should see the DEAD flag and not go > ahead with blkg_lookup()? If yes, atleast it is not obivious. We're relying on the fact that it doesn't matter anymore because all blkgs will be shoot down in queue cleanup path which goes through rcu free, which is different from deactivating individual policies. It indeed is subtle. Umm... this is starting to get ridiculous. Why the hell was megaraid messing with so many queues anyways? Thanks. -- tejun