Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752777Ab3IIKcM (ORCPT ); Mon, 9 Sep 2013 06:32:12 -0400 Received: from smtp02.citrix.com ([66.165.176.63]:22627 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752364Ab3IIKcK (ORCPT ); Mon, 9 Sep 2013 06:32:10 -0400 X-IronPort-AV: E=Sophos;i="4.90,866,1371081600"; d="scan'208";a="49544493" Message-ID: <522DA394.1020305@citrix.com> Date: Mon, 9 Sep 2013 11:31:48 +0100 From: David Vrabel User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.16) Gecko/20121215 Iceowl/1.0b1 Icedove/3.0.11 MIME-Version: 1.0 To: Konrad Rzeszutek Wilk CC: , , , , , , Konrad Rzeszutek Wilk Subject: Re: [PATCH 3/5] xen/smp: Update pv_lock_ops functions before alternative code starts under PVHVM References: <1378561605-18998-1-git-send-email-konrad.wilk@oracle.com> <1378561605-18998-4-git-send-email-konrad.wilk@oracle.com> In-Reply-To: <1378561605-18998-4-git-send-email-konrad.wilk@oracle.com> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.80.2.76] X-DLP: MIA2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2025 Lines: 49 On 07/09/13 14:46, Konrad Rzeszutek Wilk wrote: > Before this patch we would patch all of the pv_lock_ops sites > using alternative assembler. Then later in the bootup cycle > change the unlock_kick and lock_spinning to the Xen specific - > without re patching. > > That meant that for the core of the kernel we would be running > with the baremetal version of unlock_kick and lock_spinning while > for modules we would have the proper Xen specific slowpaths. > > As most of the module uses some API from the core kernel that ended > up with slowpath lockers waiting forever to be kicked (b/c they > would be using the Xen specific slowpath logic). And the > kick never came b/c the unlock path that was taken was the > baremetal one. > > On PV we do not have the problem as we initialise before the > alternative code kicks in. > > The fix is to move the updating of the pv_lock_ops function > before the alternative code starts patching. This comment seems odd. The xen_spinlock_init() call is added not moved. > --- a/arch/x86/xen/smp.c > +++ b/arch/x86/xen/smp.c > @@ -731,4 +731,12 @@ void __init xen_hvm_smp_init(void) > smp_ops.cpu_die = xen_hvm_cpu_die; > smp_ops.send_call_func_ipi = xen_smp_send_call_function_ipi; > smp_ops.send_call_func_single_ipi = xen_smp_send_call_function_single_ipi; > + > + /* > + * The alternative logic (which patches the unlock/lock) runs before > + * the smp bootup up code is activated. That meant we would never patch > + * the core of the kernel with proper paravirt interfaces but would patch > + * modules. > + */ > + xen_init_spinlocks(); PV does this in xen_smp_prepare_boot_cpu. It would be better if the PVHVM case followed this same pattern and provide a smp_prepare_boot_cpu implementation to do this? David -- 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/