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

From: Jason Wang <jasowang@redhat.com>
To: Halil Pasic <pasic@linux.ibm.com>
Cc: Cornelia Huck <cohuck@redhat.com>, mst <mst@redhat.com>,
	virtualization <virtualization@lists.linux-foundation.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Peter Zijlstra <peterz@infradead.org>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Marc Zyngier <maz@kernel.org>, eperezma <eperezma@redhat.com>,
	Cindy Lu <lulu@redhat.com>,
	Stefano Garzarella <sgarzare@redhat.com>,
	Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Subject: Re: [PATCH V4 0/9] rework on the IRQ hardening of virtio
Date: Thu, 12 May 2022 11:31:08 +0800	[thread overview]
Message-ID: <CACGkMEtaN6tZrwp3rsxu4Hn1Rev2P06X3BaR4X1cqDxnRdPCKg@mail.gmail.com> (raw)
In-Reply-To: <20220511160147.46cbf2fb.pasic@linux.ibm.com>

On Wed, May 11, 2022 at 10:02 PM Halil Pasic <pasic@linux.ibm.com> wrote:
>
> On Wed, 11 May 2022 10:22:59 +0800
> Jason Wang <jasowang@redhat.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
>