On Mon, May 16, 2022 at 01:20:06PM +0200, Halil Pasic wrote:

On Thu, 12 May 2022 11:31:08 +0800
Jason Wang [off-list ref] wrote:

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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.

Can we do some sort of an assertion that if the kernel is built with
the corresponding debug features will make sure this assumption holds
(and warn if it does not)? That assertion would also document the fact.

Lockdep will do this automatically if you get it wrong, just like it
did here.

If an assertion is not possible, I think we should at least place a
strategic comment that documents our assumption.

That can't hurt.

Regards,
Halil

quoted

Thanks

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