From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:41899) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gpBan-000795-Oy for qemu-devel@nongnu.org; Thu, 31 Jan 2019 07:37:18 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gpBam-0004Qd-Uw for qemu-devel@nongnu.org; Thu, 31 Jan 2019 07:37:17 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:36574 helo=mx0a-001b2d01.pphosted.com) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gpBam-0004QR-P7 for qemu-devel@nongnu.org; Thu, 31 Jan 2019 07:37:16 -0500 Received: from pps.filterd (m0098420.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x0VCb4Ex033258 for ; Thu, 31 Jan 2019 07:37:16 -0500 Received: from e06smtp02.uk.ibm.com (e06smtp02.uk.ibm.com [195.75.94.98]) by mx0b-001b2d01.pphosted.com with ESMTP id 2qbyprm5tg-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Thu, 31 Jan 2019 07:37:07 -0500 Received: from localhost by e06smtp02.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 31 Jan 2019 12:35:00 -0000 Date: Thu, 31 Jan 2019 13:34:55 +0100 From: Halil Pasic In-Reply-To: <20190131125220.285a4bc8.cohuck@redhat.com> References: <20190130132212.7376-1-cohuck@redhat.com> <20190130132212.7376-2-cohuck@redhat.com> <20190130195127.5ff3c849@oc2783563651> <20190131125220.285a4bc8.cohuck@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Message-Id: <20190131133455.3097613f@oc2783563651> Subject: Re: [Qemu-devel] [PATCH v3 1/6] vfio-ccw: make it safe to access channel programs List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Cornelia Huck Cc: Eric Farman , Farhan Ali , Pierre Morel , linux-s390@vger.kernel.org, kvm@vger.kernel.org, qemu-devel@nongnu.org, qemu-s390x@nongnu.org, Alex Williamson On Thu, 31 Jan 2019 12:52:20 +0100 Cornelia Huck wrote: > On Wed, 30 Jan 2019 19:51:27 +0100 > Halil Pasic wrote: > > > On Wed, 30 Jan 2019 14:22:07 +0100 > > Cornelia Huck wrote: > > > > > When we get a solicited interrupt, the start function may have > > > been cleared by a csch, but we still have a channel program > > > structure allocated. Make it safe to call the cp accessors in > > > any case, so we can call them unconditionally. > > > > I read this like it is supposed to be safe regardless of > > parallelism and threads. However I don't see any explicit > > synchronization done for cp->initialized. > > > > I've managed to figure out how is that supposed to be safe > > for the cp_free() (which is probably our main concern) in > > vfio_ccw_sch_io_todo(), but if fail when it comes to the one > > in vfio_ccw_mdev_notifier(). > > > > Can you explain us how does the synchronization work? > > You read that wrong, I don't add synchronization, I just add a check. > Now I'm confused. Does that mean we don't need synchronization for this? Regards, Halil