On 10/16/24 2:05 PM, Matthew Wilcox wrote:
> On Wed, Oct 16, 2024 at 10:23:14AM -0400, Waiman Long wrote:
>> Another alternative that I have been thinking about is a down_read() variant
>> with intention to upgrade later. This will ensure that only one active
>> reader is allowed to upgrade later. With this, upgrade_read() will always
>> succeed, maybe with some sleeping, as long as the correct down_read() is
>> used.
> How is that different from Kent's SIX locks other than you can take an
> rwsem for write immediately (SIX locks have to be taken for Intent and
> then Upgraded)?

Yes, it is modeled after Kent's SIX locks. The goal is to eventually 
eliminate the need of a separate SIX lock.

Cheers,
Longman