Re: [PATCH] rust: sync: add wait_interruptible_freezable

[Alice Ryhl]

On Mon, Feb 3, 2025 at 3:30 PM Boqun Feng <boqun.feng@xxxxxxxxx> wrote:
>
> On Mon, Feb 03, 2025 at 02:41:37PM +0100, Alice Ryhl wrote:
> > On Mon, Feb 3, 2025 at 2:38 PM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> > >
> > > On Mon, Feb 03, 2025 at 12:56:05PM +0100, Alice Ryhl wrote:
> > > > On Mon, Feb 3, 2025 at 12:54 PM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> > > > >
> > > > > On Thu, Jan 30, 2025 at 11:30:44AM +0000, Alice Ryhl wrote:
> > > > > > Binder allows you to freeze a process where some of its threads are
> > > > > > blocked on the Binder driver. To make this work, we need to pass
> > > > > > TASK_FREEZABLE when going to sleep in the appropriate places. Thus, add
> > > > > > a new method wait_interruptible_freezable for the condition variable so
> > > > > > that sleeps where this is supported can be marked as such.
> > > > >
> > > > > The constraint on freezable is that you must not hold locks. There is a
> > > > > lockdep check for this in the code, but it would probably make sense to
> > > > > teach Rust about this constraint as well, hmm?
> > > >
> > > > Unfortunately, I don't think there's any way to enforce this at
> > > > compile time, but I'm definitely happy to add this in the
> > > > documentation.
> > >
> > > Ah, ISTR people talking about teaching Rust about the whole raw_spinlock
> > > vs spinlock vs mutex nesting order and figured if it can do that, then
>
> Peter, are you talking about the POC idea I proposed on tracking irqsave
> status:
>
>         https://lore.kernel.org/rust-for-linux/20241018055125.2784186-1-boqun.feng@xxxxxxxxx/
>
> ? I'm working on this right now, however, I don't think this would help
> spinlock or mutex nesting? Because there's no global(percpu) status of
> acquiring these locks. Am I missing something here?

I assumed that Peter was talking about klint, but I don't know.

Alice