linux-kernel - Re: [PATCH vfio 1/2] hisi_acc_vfio_pci: Change reset_lock to mutex

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Message-ID: <20231128004612.GE432016@ziepe.ca>
Date:   Mon, 27 Nov 2023 20:46:12 -0400
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Shameerali Kolothum Thodi <shameerali.kolothum.thodi@...wei.com>
Cc:     Brett Creeley <brett.creeley@....com>,
        "yishaih@...dia.com" <yishaih@...dia.com>,
        liulongfang <liulongfang@...wei.com>,
        "kevin.tian@...el.com" <kevin.tian@...el.com>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "shannon.nelson@....com" <shannon.nelson@....com>
Subject: Re: [PATCH vfio 1/2] hisi_acc_vfio_pci: Change reset_lock to
 mutex_lock

On Fri, Nov 24, 2023 at 08:46:58AM +0000, Shameerali Kolothum Thodi wrote:
> > diff --git a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
> > b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
> > index b2f9778c8366..2c049b8de4b4 100644
> > --- a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
> > +++ b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
> > @@ -638,17 +638,17 @@ static void
> >  hisi_acc_vf_state_mutex_unlock(struct hisi_acc_vf_core_device
> > *hisi_acc_vdev)
> >  {
> >  again:
> > -	spin_lock(&hisi_acc_vdev->reset_lock);
> > +	mutex_lock(&hisi_acc_vdev->reset_mutex);
> >  	if (hisi_acc_vdev->deferred_reset) {
> >  		hisi_acc_vdev->deferred_reset = false;
> > -		spin_unlock(&hisi_acc_vdev->reset_lock);
> > +		mutex_unlock(&hisi_acc_vdev->reset_mutex);
> 
> Don't think we have that sleeping while atomic case for this here.
> Same for mlx5 as well. But if the idea is to have a common locking
> across vendor drivers, it is fine.

Yeah, I'm not sure about changing spinlocks to mutex's for no reason..
If we don't sleep and don't hold it for very long then the spinlock is
appropriate

Jason