Re: [PATCH 0/8] Introduce simple hazard pointers for lockdep

On 2025-06-26 06:16, Christoph Hellwig wrote:
> On Wed, Jun 25, 2025 at 07:08:57AM -0700, Boqun Feng wrote:
>> Sure, I will put one for the future version, here is the gist:
> 
> Thanks a lot!
> 
>> The updater's wait can finish immediately if no one is accessing 'a', in
>> other words it doesn't need to wait for reader 2.
> 
> So basically it is the RCU concept, but limited to protecting exactly
> one pointer update per critical section with no ability for the read
> to e.g. acquire a refcount on the objected pointed to by that pointer?

FWIW, hazard pointers can be chained with other existence guarantee
mechanisms. I've done prototypes that use hazard pointers chained
with a reference counter in the object to implement something similar to
smart pointers. Let me know if you are interested in the details.

Thanks,

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com