Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754668Ab0AURsp (ORCPT ); Thu, 21 Jan 2010 12:48:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752900Ab0AURso (ORCPT ); Thu, 21 Jan 2010 12:48:44 -0500 Received: from mx1.redhat.com ([209.132.183.28]:44043 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753912Ab0AURsn (ORCPT ); Thu, 21 Jan 2010 12:48:43 -0500 Date: Thu, 21 Jan 2010 19:45:38 +0200 From: "Michael S. Tsirkin" To: Avi Kivity Cc: Davide Libenzi , mtosatti@redhat.com, kvm@vger.kernel.org, Linux Kernel Mailing List Subject: Re: [PATCHv2 1/3] eventfd: allow atomic read and waitqueue remove Message-ID: <20100121174538.GG16707@redhat.com> References: <20100121162648.GA16458@redhat.com> <4B588B29.2050100@redhat.com> <20100121172336.GA16707@redhat.com> <4B588FCE.7030803@redhat.com> <20100121173259.GC16707@redhat.com> <4B58933C.4090209@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4B58933C.4090209@redhat.com> User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 686 Lines: 20 On Thu, Jan 21, 2010 at 07:47:40PM +0200, Avi Kivity wrote: > On 01/21/2010 07:32 PM, Michael S. Tsirkin wrote: >> >>> Can't you read from the file? >>> >> IMO no, the read could block. >> > > But you're in process context. An eventfd never blocks. Yes it blocks if counter is 0. And we don't know it's not 0 unless we read :) catch-22. > -- > Do not meddle in the internals of kernels, for they are subtle and quick to panic. -- 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/