Re: [PATCH v2] locking/rwbase: Prevent indefinite writer starvation

[Davidlohr Bueso]

On Thu, 19 Jan 2023, Mel Gorman wrote:

> The race could be closed by moving wait_lock acquisition before the
> atomic_sub in rwbase_write_lock() but it expands the scope of the wait_lock
> and I'm not sure that's necessary for either correctness or preventing
> writer starvation. It's a more straight-forward fix but expanding the
> scope of a lock unnecessarily has been unpopular in the past.

Curiously, this is the documented behavior:

 * down_write/write_lock()
 *  1) Lock rtmutex
 *  2) Remove the reader BIAS to force readers into the slow path