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Mon, 12 Jul 2021 23:38:25 +0000 (GMT) Received: from li-e979b1cc-23ba-11b2-a85c-dfd230f6cf82 (unknown [9.171.38.94]) by d06av26.portsmouth.uk.ibm.com (Postfix) with SMTP; Mon, 12 Jul 2021 23:38:25 +0000 (GMT) Date: Tue, 13 Jul 2021 01:38:15 +0200 From: Halil Pasic To: Tony Krowiak Cc: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, borntraeger@de.ibm.com, cohuck@redhat.com, pasic@linux.vnet.ibm.com, jjherne@linux.ibm.com, jgg@nvidia.com, alex.williamson@redhat.com, kwankhede@nvidia.com, frankja@linux.ibm.com, david@redhat.com, imbrenda@linux.ibm.com, hca@linux.ibm.com Subject: Re: [PATCH] s390/vfio-ap: do not open code locks for VFIO_GROUP_NOTIFY_SET_KVM notification Message-ID: <20210713013815.57e8a8cb.pasic@linux.ibm.com> In-Reply-To: <20210707154156.297139-1-akrowiak@linux.ibm.com> References: <20210707154156.297139-1-akrowiak@linux.ibm.com> Organization: IBM X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.32; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: CIgMDj5PHlNuppKgQ2pjdngNUNlPvsTD X-Proofpoint-GUID: GrPPd0Hiiyaa667Lp2Y7ATqxK_iUBbcm X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.790 definitions=2021-07-12_14:2021-07-12,2021-07-12 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 lowpriorityscore=0 malwarescore=0 impostorscore=0 bulkscore=0 phishscore=0 suspectscore=0 mlxscore=0 adultscore=0 priorityscore=1501 spamscore=0 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2107120160 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 7 Jul 2021 11:41:56 -0400 Tony Krowiak wrote: > It was pointed out during an unrelated patch review that locks should not > be open coded - i.e., writing the algorithm of a standard lock in a > function instead of using a lock from the standard library. The setting and > testing of the kvm_busy flag and sleeping on a wait_event is the same thing > a lock does. Whatever potential deadlock was found and reported via the > lockdep splat was not magically removed by going to a wait_queue; it just > removed the lockdep annotations that would identify the issue early Did you change your opinion since we last talked about it? This reads to me like we are deadlocky without this patch, because of the last sentence. Regards, Halil