From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752254AbeFEOVN (ORCPT ); Tue, 5 Jun 2018 10:21:13 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:33780 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751685AbeFEOVM (ORCPT ); Tue, 5 Jun 2018 10:21:12 -0400 Reply-To: pmorel@linux.ibm.com Subject: Re: [PATCH v2 06/10] vfio: ccw: Make FSM functions atomic To: Cornelia Huck Cc: Pierre Morel , pasic@linux.vnet.ibm.com, bjsdjshi@linux.vnet.ibm.com, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org References: <1527243678-3140-1-git-send-email-pmorel@linux.vnet.ibm.com> <1527243678-3140-7-git-send-email-pmorel@linux.vnet.ibm.com> <20180605133850.3509a3d3.cohuck@redhat.com> <46613ac7-3156-7a78-7d49-acbc3f615b76@linux.ibm.com> <20180605153539.1eee99f9.cohuck@redhat.com> From: Pierre Morel Date: Tue, 5 Jun 2018 16:21:03 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: <20180605153539.1eee99f9.cohuck@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-TM-AS-GCONF: 00 x-cbid: 18060514-0008-0000-0000-000002446540 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18060514-0009-0000-0000-000021AA6B11 Message-Id: <6c39016f-8125-c5cc-3b9b-0bc517e5f642@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-06-05_05:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1805220000 definitions=main-1806050165 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/06/2018 15:35, Cornelia Huck wrote: > On Tue, 5 Jun 2018 15:10:11 +0200 > Pierre Morel wrote: > >> On 05/06/2018 13:38, Cornelia Huck wrote: >>> On Fri, 25 May 2018 12:21:14 +0200 >>> Pierre Morel wrote: >>> >>>> We use mutex around the FSM function call to make the FSM >>>> event handling and state change atomic. >>> I'm still not really clear as to what this mutex is supposed to >>> serialize: >>> >>> - Modification of the state? >>> - Any calls in the state machine? >>> - A combination? (That would imply that we only deal with the state in >>> the state machine.) >> yes to all > But wouldn't that imply that you need to either take the mutex if you > do something dependent on the state, or fire an event in that case? Yes, if it is not I forgot something important (like I did in patch 10) vfio_ccw_fsm_event(private, event) takes the mutex on firering an event. I have some cases where I do not respect this. This is false and I must handle this with a new private variable, this is where I test the state after having fired an event. I will need to change this, in quiesce, reset, probe and open (others?). > >>> >>>> Signed-off-by: Pierre Morel >>>> --- >>>> drivers/s390/cio/vfio_ccw_drv.c | 3 +-- >>>> drivers/s390/cio/vfio_ccw_private.h | 3 +++ >>>> 2 files changed, 4 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c >>>> index 6b7112e..98951d5 100644 >>>> --- a/drivers/s390/cio/vfio_ccw_drv.c >>>> +++ b/drivers/s390/cio/vfio_ccw_drv.c >>>> @@ -73,8 +73,6 @@ static void vfio_ccw_sch_io_todo(struct work_struct *work) >>>> >>>> private = container_of(work, struct vfio_ccw_private, io_work); >>>> vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_INTERRUPT); >>>> - if (private->mdev) >>>> - private->state = VFIO_CCW_STATE_IDLE; >>> Looks like an unrelated change? If you want to do all state changes >>> under the mutex, that should rather be moved than deleted, shouldn't it? >> It is moved to fsm_irq() which is called under mutex. >> fsm_irq() returns VFIO_CCW_STATE_IDLE. > So, should that go into another patch? I will see if I can put it inside the patch 01/10 moving state change out of IRQ context. -- Pierre Morel Linux/KVM/QEMU in Böblingen - Germany