linux-kernel - Re: [PATCH V4 0/9] rework on the IRQ hardening of virtio

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Date:   Thu, 12 May 2022 11:31:08 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Halil Pasic <pasic@...ux.ibm.com>
Cc:     Cornelia Huck <cohuck@...hat.com>, mst <mst@...hat.com>,
        virtualization <virtualization@...ts.linux-foundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Marc Zyngier <maz@...nel.org>, eperezma <eperezma@...hat.com>,
        Cindy Lu <lulu@...hat.com>,
        Stefano Garzarella <sgarzare@...hat.com>,
        Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Subject: Re: [PATCH V4 0/9] rework on the IRQ hardening of virtio

On Wed, May 11, 2022 at 10:02 PM Halil Pasic <pasic@...ux.ibm.com> wrote:
>
> On Wed, 11 May 2022 10:22:59 +0800
> Jason Wang <jasowang@...hat.com> wrote:
>
> > >        CPU0
> > >        ----
> > >   lock(&vcdev->irq_lock);
> > >   <Interrupt>
> > >     lock(&vcdev->irq_lock);
> > >
> > >  *** DEADLOCK ***
> >
> > It looks to me we need to use write_lock_irq()/write_unlock_irq() to
> > do the synchronization.
> >
> > And we probably need to keep the
> > read_lock_irqsave()/read_lock_irqrestore() logic since I can see the
> > virtio_ccw_int_handler() to be called from process context (e.g from
> > the io_subchannel_quiesce()).
> >
>
> Sounds correct.

As Cornelia and Vineeth pointed out, all the paths the vring_interrupt
is called with irq disabled.

So I will use spin_lock()/spin_unlock() in the next version.

Thanks

>
> Regards,
> Halil
>