Re: [PATCH v5 0/3] rust: add `ww_mutex` support

[Daniel Almeida <daniel.almeida@collabora.com>]

Hi Onur,

> On 14 Aug 2025, at 08:13, Onur Özkan <work@onurozkan.dev> wrote:
> 
> Hi all,
> 
> I have been brainstorming on the auto-unlocking (on dynamic number of
> mutexes) idea we have been discussing for some time.
> 
> There is a challange with how we handle lock guards and my current
> thought is to remove direct data dereferencing from guards. Instead,
> data access would only be possible through a fallible method (e.g.,
> `try_get`). If the guard is no longer valid, this method would fail to
> not allow data-accessing after auto-unlock.
> 
> In practice, it would work like this:
> 
> let a_guard = ctx.lock(mutex_a)?;
> let b_guard = ctx.lock(mutex_b)?;
> 
> // Suppose user tries to lock `mutex_c` without aborting the
> // entire function (for some reason). This means that even on
> // failure, `a_guard` and `b_guard` will still be accessible.
> if let Ok(c_guard) = ctx.lock(mutex_c) {
>     // ...some logic
> }
> 
> let a_data = a_guard.try_get()?;
> let b_data = b_guard.try_get()?;

Can you add more code here? How is this going to look like with the two
closures we’ve been discussing?

> 
> If user wants to access the data protected by `a_guard` or `b_guard`,
> they must call `try_get()`. This will only succeed if the guard is
> still valid (i.e., it hasn't been automatically unlocked by a failed
> `lock(mutex_c)` call due to `EDEADLK`). This way, data access after an
> auto-unlock will be handled safely.
> 
> Any thoughts/suggestions?
> 
> Regards,
> Onur
> 

— Daniel