Re: [PATCH v3 1/3] rust: Introduce irq module

[Lyude Paul]

On Thu, 2024-08-15 at 21:46 +0000, Benno Lossin wrote:
> I don't see the utility of this, if you already have an `IrqDisabled`,
> then you don't need to call `with_irqs_disabled`. If you don't have one,
> irqs still might be disabled, but you don't know.
> 
> > Granted - I have no idea how ergonomic something like this would be since on
> > the C side of things: we don't really require that the user know the prior IRQ
> > state for things like irqsave/irqrestore functions.
> 
> I think ergonomically, this is a bad idea, since it will infect a lot of
> functions that don't care about IRQ.

Yeah, I figured that might be the case.

So - I'm starting to lean towards making `with_irqs_disabled` an unsafe
function then where part of the safety contract is "The interrupt state must
never be changed within the closure unless the user ensures it relinquishes
access to the IrqDisabled token before doing so.". Would that work?

It would have been nice for this function to be safe, but I don't think that's
too difficult of a safety contract to uphold (especially when we have things
like lockdep that will tell us if we violate it anyway). Especially
considering this is more or less the requirements that C code has to uphold
already.

-- 
Cheers,
 Lyude Paul (she/her)
 Software Engineer at Red Hat

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