linux-kernel - RE: [RFC 01/20] iommu/iommufd: Add /dev/iommu core

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Message-ID: <PH0PR11MB5658E36269B5A490EADE417FC3B99@PH0PR11MB5658.namprd11.prod.outlook.com>
Date:   Fri, 15 Oct 2021 11:29:38 +0000
From:   "Liu, Yi L" <yi.l.liu@...el.com>
To:     Jason Gunthorpe <jgg@...dia.com>
CC:     "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "hch@....de" <hch@....de>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "jean-philippe@...aro.org" <jean-philippe@...aro.org>,
        "Tian, Kevin" <kevin.tian@...el.com>,
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        "Raj, Ashok" <ashok.raj@...el.com>,
        "yi.l.liu@...ux.intel.com" <yi.l.liu@...ux.intel.com>,
        "Tian, Jun J" <jun.j.tian@...el.com>, "Wu, Hao" <hao.wu@...el.com>,
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        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
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Subject: RE: [RFC 01/20] iommu/iommufd: Add /dev/iommu core

> From: Jason Gunthorpe <jgg@...dia.com>
> Sent: Friday, October 15, 2021 7:18 PM
> 
> On Fri, Oct 15, 2021 at 09:18:06AM +0000, Liu, Yi L wrote:
> 
> > >   Acquire from the xarray is
> > >    rcu_lock()
> > >    ioas = xa_load()
> > >    if (ioas)
> > >       if (down_read_trylock(&ioas->destroying_lock))
> >
> > all good suggestions, will refine accordingly. Here destroying_lock is a
> > rw_semaphore. right? Since down_read_trylock() accepts a rwsem.
> 
> Yes, you probably need a sleeping lock

got it. thanks,

Regards,
Yi Liu