[PATCH 1/2] mm/vmscan: add sync_shrinkers function v2

[Andrew Morton]

On Fri, 20 Aug 2021 14:05:27 +0200 "Christian König" <ckoenig.leichtzumerken at gmail.com> wrote:

> While unplugging a device the TTM shrinker implementation
> needs a barrier to make sure that all concurrent shrink
> operations are done and no other CPU is referring to a
> device specific pool any more.
> 
> Taking and releasing the shrinker semaphore on the write
> side after unmapping and freeing all pages from the device
> pool should make sure that no shrinker is running in
> paralell.
> 
> This allows us to avoid the contented mutex in the TTM pool
> implementation for every alloc/free operation.
> 
> v2: rework the commit message to make clear why we need this

Acked-by: Andrew Morton <akpm at linux-foundation.org>