From: Jason Gunthorpe <jgg@nvidia.com>
To: Halil Pasic <pasic@linux.ibm.com>
Cc: Tony Krowiak <akrowiak@linux.ibm.com>,
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,
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
Date: Tue, 13 Jul 2021 14:05:33 -0300 [thread overview]
Message-ID: <20210713170533.GF136586@nvidia.com> (raw)
In-Reply-To: <20210713184517.48eacee6.pasic@linux.ibm.com>
On Tue, Jul 13, 2021 at 06:45:17PM +0200, Halil Pasic wrote:
> Jason may give it another try to convince us that 0cc00c8d4050 only
> silenced lockdep, but vfio_ap remained prone to deadlocks. To my best
> knowledge using condition variable and a mutex is one of the well known
> ways to implement an rwlock.
The well known pattern is to use a rwsem.
This:
wait_event_cmd(matrix_mdev->wait_for_kvm,
!matrix_mdev->kvm_busy,
mutex_unlock(&matrix_dev->lock),
mutex_lock(&matrix_dev->lock));
Is not really a rwsem, and is invsible to lockdep.
Jason
next prev parent reply other threads:[~2021-07-13 17:05 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-07 15:41 [PATCH] s390/vfio-ap: do not open code locks for VFIO_GROUP_NOTIFY_SET_KVM notification Tony Krowiak
2021-07-12 13:42 ` Tony Krowiak
2021-07-12 23:38 ` Halil Pasic
2021-07-13 13:48 ` Tony Krowiak
2021-07-13 16:45 ` Halil Pasic
2021-07-13 17:05 ` Jason Gunthorpe [this message]
2021-07-13 19:04 ` Tony Krowiak
2021-07-13 19:21 ` Jason Gunthorpe
2021-07-14 13:25 ` Tony Krowiak
2021-07-14 17:56 ` Christian Borntraeger
2021-07-14 18:43 ` Jason Gunthorpe
2021-07-14 19:02 ` Alex Williamson
2021-07-15 11:31 ` Halil Pasic
2021-07-15 14:57 ` Jason Gunthorpe
2021-07-13 18:47 ` Tony Krowiak
2021-07-15 13:44 ` Halil Pasic
2021-07-15 14:38 ` Tony Krowiak
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