[Intel-gfx] [PATCH 2/2] drm/i915: Removing polling for struct_mutex from vmap shrinker

[Chris Wilson]

Quoting Tvrtko Ursulin (2019-01-10 10:28:14)
> 
> On 09/01/2019 16:42, Chris Wilson wrote:
> > The wait-for-idle used from within the shrinker_lock_uninterruptible
> > depends on the struct_mutex locking state being known and declared to
> > i915_request_wait(). As it is conceivable that we reach the vmap
> > notifier from underneath struct_mutex (and so keep on relying on the
> > mutex_trylock_recursive), we should not blindly call i915_request_wait.
> > 
> > In the process we can remove the dubious polling to acquire
> > struct_mutex, and simply act, or not, on a successful trylock.
> 
> Makes sense and removes the special casing. I only miss the historical 
> reference as to why did vmap notifier need this special handling?

Cargo culting. I copied the code I had for oom-notifier, thinking the
heavier the hammer the better.
-Chris