Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757312AbaFYPyy (ORCPT ); Wed, 25 Jun 2014 11:54:54 -0400 Received: from cantor2.suse.de ([195.135.220.15]:43931 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756887AbaFYPyx (ORCPT ); Wed, 25 Jun 2014 11:54:53 -0400 Date: Wed, 25 Jun 2014 17:54:50 +0200 (CEST) From: Jiri Kosina To: One Thousand Gnomes cc: Jiri Slaby , linux-kernel@vger.kernel.org, tj@kernel.org, rostedt@goodmis.org, mingo@redhat.com, akpm@linux-foundation.org, andi@firstfloor.org, paulmck@linux.vnet.ibm.com, pavel@ucw.cz, jirislaby@gmail.com, Vojtech Pavlik , Michael Matz Subject: Re: [PATCH 00/21] kGraft In-Reply-To: <20140625135421.67cd5f5f@alan.etchedpixels.co.uk> Message-ID: References: <1403694329-3064-1-git-send-email-jslaby@suse.cz> <20140625135421.67cd5f5f@alan.etchedpixels.co.uk> User-Agent: Alpine 2.00 (LNX 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 25 Jun 2014, One Thousand Gnomes wrote: > > this is a repost of the second round of RFC on kGraft, the linux > > kernel online patching developed at SUSE. This repost only widened the > > target audience for broader review, no code change happened. > > - wait_event_freezable(khubd_wait, > + wait_event_freezable(khubd_wait, > ({ kgr_task_safe(current); > > The changes are somewhat ugly with all the kgraft crap leaking into plces > like jbd and freezer and usb. That says to me its not well isolated and > there must be a better way of hiding that kgr stuff so we don't have to > kepe putting more code into all the kthreads, and inevitably missing them > or have people getting it wrong. Tejun commented on this very issue during the first RFC submission a couple weeks ago. Part of his proposal was actually to take this as a good pretext to review the existing kernel threads, as the idea is that a big portion of those could easily be converted to workqueues. It of course has its own implications, such as not being able to prioritize that easily, but there is probably a lot of low-hanging fruits where driver authors and their grandmas have been creating kthreads where workqueue would suffice. But it's a very long term goal, and it's probably impractical to make kGraft dependent on it. > You add instructions to various hotpaths (despite the CONFIG comment). Kernel entry is hidden behind _TIF_WORK_SYSCALL_ENTRY and _TIF_ALLWORK_MASK, so it doesn't add any overhead if kGraft is not enabled. What other hot paths do you refer to? > Don't get me wrong - I'd like a good working ksplice/graft ! Thanks Alan, -- Jiri Kosina SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/