From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: [PATCH v4 2/9] KVM: Switch IRQ subsystem to SRCU Date: Tue, 09 Nov 2010 12:21:46 +0100 Message-ID: <4CD92ECA.1040508@siemens.com> References: <8cee16e41fc414c185e1d7c170ce44da19797fc1.1289215310.git.jan.kiszka@siemens.com> <4CD92722.2060908@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , kvm , Alex Williamson , "Michael S. Tsirkin" To: Avi Kivity Return-path: Received: from david.siemens.de ([192.35.17.14]:16235 "EHLO david.siemens.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753605Ab0KILWF (ORCPT ); Tue, 9 Nov 2010 06:22:05 -0500 In-Reply-To: <4CD92722.2060908@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: Am 09.11.2010 11:49, Avi Kivity wrote: > On 11/08/2010 01:21 PM, Jan Kiszka wrote: >> Ack and mask notifiers typically call back into kvm_set_irq, thus may >> iterate over all VCPUs of a VM. Better keep this path preemptible to >> prevent that user-space can massivle influence scheduling latencies. Use >> sleepable RCU for the protection of irq_routing and the notfier lists. >> > > What about preemptible RCU, now in mainline? Granted, that would resolve the preemption issue but not allow to use sleepy locks inside this section (as done by the last patch in this series). Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux