Re: [RFC PATCH 1/4] hazptr: Add initial implementation of hazard pointers

[Jonas Oberhauser <jonas.oberhauser@huaweicloud.com>]

Am 9/19/2024 um 8:56 AM schrieb Boqun Feng:
> On Wed, Sep 18, 2024 at 11:17:37PM +0800, Alan Huang wrote:
> [...]
>>> +#define hazptr_tryprotect(hzp, gp, field) (typeof(gp))__hazptr_tryprotect(hzp, (void **)&(gp), offsetof(typeof(*gp), field))
>>> +#define hazptr_protect(hzp, gp, field) ({ \
>>> + typeof(gp) ___p; \
>>> + \
>>> + ___p = hazptr_tryprotect(hzp, gp, field); \
>>> + BUG_ON(!___p); \
>>
>> hazptr_tryprotect might return NULL, do you need a loop here?
>>
> 
> Thanks for the review. It's me who didn't do a good job here on the
> documentation. hazptr_protect() is supposed to use for the case where
> readers know the gp won't change.
> 
> Regards,
> Boqun
> 
>>> + ___p; \
>>> +})
>>> +

Oh, disregard my other e-mail, I hadn't seen this discussion.

Do you have any specific use case of this in mind? If you know that the 
pointer can't change, I would assume you can also just read the pointer 
normally and assign to the hazard pointer without a fence, no?

have fun, jonas