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Sat, 14 Nov 2020 00:00:22 +0000 (GMT) Received: from d06av24.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3032D4204F; Sat, 14 Nov 2020 00:00:22 +0000 (GMT) Received: from oc2783563651 (unknown [9.171.46.164]) by d06av24.portsmouth.uk.ibm.com (Postfix) with SMTP; Sat, 14 Nov 2020 00:00:22 +0000 (GMT) Date: Sat, 14 Nov 2020 01:00:20 +0100 From: Halil Pasic To: Tony Krowiak Cc: Harald Freudenberger , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, borntraeger@de.ibm.com, cohuck@redhat.com, mjrosato@linux.ibm.com, alex.williamson@redhat.com, kwankhede@nvidia.com, fiuczy@linux.ibm.com, frankja@linux.ibm.com, david@redhat.com, hca@linux.ibm.com, gor@linux.ibm.com Subject: Re: [PATCH v11 04/14] s390/zcrypt: driver callback to indicate resource in use Message-ID: <20201114010020.381277c2.pasic@linux.ibm.com> In-Reply-To: References: <20201022171209.19494-1-akrowiak@linux.ibm.com> <20201022171209.19494-5-akrowiak@linux.ibm.com> <42f3f4f9-6263-cb1e-d882-30b62236a594@linux.ibm.com> Organization: IBM X-Mailer: Claws Mail 3.11.1 (GTK+ 2.24.31; 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-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.312,18.0.737 definitions=2020-11-13_21:2020-11-13,2020-11-13 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 bulkscore=0 spamscore=0 malwarescore=0 priorityscore=1501 adultscore=0 impostorscore=0 mlxlogscore=999 clxscore=1015 suspectscore=0 mlxscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2011130151 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Fri, 13 Nov 2020 16:30:31 -0500 Tony Krowiak wrote: > We will be using the mutex_trylock() function in our sysfs > assignment > interfaces which make the call to the AP bus to check permissions (which > also > locks ap_perms). If the mutex_trylock() fails, we return from the assignment > function with -EBUSY. This should resolve that potential deadlock issue. It resolves the deadlock issue only if in_use() is also doing mutex_trylock(), but the if in_use doesn't take the lock it needs to back off (and so does it's client code) i.e. a boolean as return value won't do. Regards, Halil