[Intel-gfx] [PATCH 1/2] drm/i915: Use mutex_lock_killable() from inside the shrinker

[Tvrtko Ursulin]

On 09/01/2019 16:42, Chris Wilson wrote:
> If the current process is being killed (it was interrupted with SIGKILL
> or equivalent), it will not make any progress in page allocation and we
> can abort performing the shrinking on its behalf. So we can use
> mutex_lock_killable() instead (although this path should only be
> reachable from kswapd currently).

kswapd is hopefully not killable so it is not reachable via that route. 
But should be via other i915_gem_shrink_all callers. Is it starting to 
look like we need to pass some flags to say 
normal/interruptible/killable (kswapd/debugfs/?)?

Regards,

Tvrtko

> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> ---
>   drivers/gpu/drm/i915/i915_gem_shrinker.c | 10 +++++-----
>   1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_shrinker.c b/drivers/gpu/drm/i915/i915_gem_shrinker.c
> index 34b108f73f1d..8ad9519779cc 100644
> --- a/drivers/gpu/drm/i915/i915_gem_shrinker.c
> +++ b/drivers/gpu/drm/i915/i915_gem_shrinker.c
> @@ -39,18 +39,18 @@ static bool shrinker_lock(struct drm_i915_private *i915,
>   			  unsigned int flags,
>   			  bool *unlock)
>   {
> -	switch (mutex_trylock_recursive(&i915->drm.struct_mutex)) {
> +	struct mutex *m = &i915->drm.struct_mutex;
> +
> +	switch (mutex_trylock_recursive(m)) {
>   	case MUTEX_TRYLOCK_RECURSIVE:
>   		*unlock = false;
>   		return true;
>   
>   	case MUTEX_TRYLOCK_FAILED:
>   		*unlock = false;
> -		if (flags & I915_SHRINK_ACTIVE) {
> -			mutex_lock_nested(&i915->drm.struct_mutex,
> -					  I915_MM_SHRINKER);
> +		if (flags & I915_SHRINK_ACTIVE &&
> +		    mutex_lock_killable_nested(m, I915_MM_SHRINKER) == 0)
>   			*unlock = true;
> -		}
>   		return *unlock;
>   
>   	case MUTEX_TRYLOCK_SUCCESS:
>