Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758341Ab1BKWc4 (ORCPT ); Fri, 11 Feb 2011 17:32:56 -0500 Received: from blu0-omc1-s13.blu0.hotmail.com ([65.55.116.24]:63763 "EHLO blu0-omc1-s13.blu0.hotmail.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757891Ab1BKWcz (ORCPT ); Fri, 11 Feb 2011 17:32:55 -0500 X-Originating-IP: [174.91.193.52] X-Originating-Email: [pdumas9@sympatico.ca] Message-ID: Date: Fri, 11 Feb 2011 17:32:49 -0500 From: Mathieu Desnoyers To: Jason Baron CC: Peter Zijlstra , hpa@zytor.com, rostedt@goodmis.org, mingo@elte.hu, tglx@linutronix.de, andi@firstfloor.org, roland@redhat.com, rth@redhat.com, masami.hiramatsu.pt@hitachi.com, fweisbec@gmail.com, avi@redhat.com, davem@davemloft.net, sam@ravnborg.org, ddaney@caviumnetworks.com, michael@ellerman.id.au, linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/2] jump label: 2.6.38 updates References: <1297452328.5226.89.camel@laptop> <1297460297.5226.99.camel@laptop> <20110211222742.GB9148@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Content-Disposition: inline In-Reply-To: <20110211222742.GB9148@redhat.com> X-Editor: vi X-Info: http://krystal.dyndns.org:8080 X-Operating-System: Linux/2.6.27.31-grsec (i686) X-Uptime: 17:30:54 up 310 days, 8:20, 6 users, load average: 0.13, 0.14, 0.09 User-Agent: Mutt/1.5.18 (2008-05-17) X-OriginalArrivalTime: 11 Feb 2011 22:32:53.0877 (UTC) FILETIME=[9F8B2A50:01CBCA3B] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2505 Lines: 84 * Jason Baron (jbaron@redhat.com) wrote: > On Fri, Feb 11, 2011 at 05:20:25PM -0500, Mathieu Desnoyers wrote: > > * Peter Zijlstra (peterz@infradead.org) wrote: > > > On Fri, 2011-02-11 at 16:13 -0500, Mathieu Desnoyers wrote: > > > > > > > > Thoughts ? > > > > > > #if defined(CC_HAVE_ASM_GOTO) && defined(CONFIG_JUMP_LABEL) > > > + > > > +struct jump_label_key { > > > + void *ptr; > > > +}; > > > > > > struct jump_label_entry { > > > struct hlist_node hlist; > > > struct jump_entry *table; > > > - int nr_entries; > > > /* hang modules off here */ > > > struct hlist_head modules; > > > unsigned long key; > > > + u32 nr_entries; > > > + int refcount; > > > }; > > > > > > #else > > > > > > +struct jump_label_key { > > > + int state; > > > +}; > > > > > > #endif > > > > > > So why can't we make that jump_label_entry::refcount and > > > jump_label_key::state an atomic_t and be done with it? > > > > > > Then the enabled case uses if (atomic_inc_return(&key->ptr->refcount) == > > > 1), and the disabled atomic_inc(&key->state). > > > > > > > OK, by "enabled" you mean #if defined(CC_HAVE_ASM_GOTO) && > > defined(CONFIG_JUMP_LABEL), and "disabled", the #else. > > > > I guess the only downside is the extra volatile for the atomic_read for > > the fallback case, which is not really much of problem realistically > > speaking: anyway, the volatile is a good thing to have in the fallback > > case to force the compiler to re-read the variable. Let's go with your > > idea. > > > > Thanks, > > > > Mathieu > > > > ok, I'll try and re-spin the interface based around atomic_t, if we are all > agreed...there was also a circular dependency issue with atomic.h including > kernel.h which included jump_label.h, and that was why we had a separate, > jump_label_ref.h header file, but hopefully I can be resolve that in a clean > way. See spinlocks ? jump_label_types.h (structure definitions, includes types.h, included from kernel.h) jump_label.h (prototypes, inline functions, includes atomic.h) Thanks, Mathieu > > thanks, > > -Jason -- Mathieu Desnoyers Operating System Efficiency R&D Consultant EfficiOS Inc. http://www.efficios.com -- 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/