From: Jim Harris <jim.harris@samsung.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: Leon Romanovsky <leonro@nvidia.com>,
Alex Williamson <alex.williamson@redhat.com>,
"bhelgaas@google.com" <bhelgaas@google.com>,
"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"ben@nvidia.com" <ben@nvidia.com>,
"pierre.cregut@orange.com" <pierre.cregut@orange.com>
Subject: Re: Locking between vfio hot-remove and pci sysfs sriov_numvfs
Date: Fri, 8 Dec 2023 20:09:34 +0000 [thread overview]
Message-ID: <ZXN3+dHzM1N5b7r+@ubuntu> (raw)
In-Reply-To: <20231208194159.GS2692119@nvidia.com>
On Fri, Dec 08, 2023 at 03:41:59PM -0400, Jason Gunthorpe wrote:
> On Fri, Dec 08, 2023 at 05:07:22PM +0000, Jim Harris wrote:
> >
> > Maybe for now we just whack this specific mole with a separate mutex
> > for synchronizing access to sriov->num_VFs in the sysfs paths?
> > Something like this (tested on my system):
>
> TBH, I don't have the time right now to unpack this locking
> mystery. Maybe Leon remembers?
>
> device_lock() gets everywhere and does a lot of different stuff, so I
> would be surprised if it was so easy..
The store() side still keeps the device_lock(), it just also acquires this
new sriov lock. So store() side should observe zero differences. The only
difference is now the show() side can acquire just the more-granular lock,
since it is only trying to synchronize on sriov->num_VFs with the store()
side. But maybe I'm missing something subtle here...
Adding Pierre who authored the 35ff867b7 commit.
next prev parent reply other threads:[~2023-12-08 20:09 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20231207223824uscas1p27dd91f0af56cda282cd28046cc981fe9@uscas1p2.samsung.com>
2023-12-07 22:38 ` Locking between vfio hot-remove and pci sysfs sriov_numvfs Jim Harris
2023-12-07 23:21 ` Alex Williamson
2023-12-07 23:48 ` Jason Gunthorpe
2023-12-08 17:07 ` Jim Harris
2023-12-08 19:41 ` Jason Gunthorpe
2023-12-08 20:09 ` Jim Harris [this message]
2023-12-10 19:05 ` Jason Gunthorpe
2023-12-11 7:20 ` Leon Romanovsky
2023-12-12 21:34 ` Jim Harris
2023-12-13 6:55 ` Leon Romanovsky
2023-12-08 17:38 ` Jim Harris
2023-12-08 17:41 ` Jason Gunthorpe
2023-12-08 17:59 ` Jim Harris
2023-12-08 18:01 ` Jason Gunthorpe
2023-12-08 18:12 ` Alex Williamson
2023-12-08 19:43 ` Jason Gunthorpe
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