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

[Tvrtko Ursulin]

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 I only miss the historical 
reference as to why did vmap notifier need this special handling?

> 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 | 35 +++---------------------
>   1 file changed, 4 insertions(+), 31 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_shrinker.c b/drivers/gpu/drm/i915/i915_gem_shrinker.c
> index 8ad9519779cc..6cc2b964c955 100644
> --- a/drivers/gpu/drm/i915/i915_gem_shrinker.c
> +++ b/drivers/gpu/drm/i915/i915_gem_shrinker.c
> @@ -385,31 +385,6 @@ i915_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
>   	return sc->nr_scanned ? freed : SHRINK_STOP;
>   }
>   
> -static bool
> -shrinker_lock_uninterruptible(struct drm_i915_private *i915, bool *unlock,
> -			      int timeout_ms)
> -{
> -	unsigned long timeout = jiffies + msecs_to_jiffies_timeout(timeout_ms);
> -
> -	do {
> -		if (i915_gem_wait_for_idle(i915,
> -					   0, MAX_SCHEDULE_TIMEOUT) == 0 &&
> -		    shrinker_lock(i915, 0, unlock))
> -			break;
> -
> -		schedule_timeout_killable(1);
> -		if (fatal_signal_pending(current))
> -			return false;
> -
> -		if (time_after(jiffies, timeout)) {
> -			pr_err("Unable to lock GPU to purge memory.\n");
> -			return false;
> -		}
> -	} while (1);
> -
> -	return true;
> -}
> -
>   static int
>   i915_gem_shrinker_oom(struct notifier_block *nb, unsigned long event, void *ptr)
>   {
> @@ -461,16 +436,14 @@ i915_gem_shrinker_vmap(struct notifier_block *nb, unsigned long event, void *ptr
>   	struct i915_vma *vma, *next;
>   	unsigned long freed_pages = 0;
>   	bool unlock;
> -	int ret;
>   
> -	if (!shrinker_lock_uninterruptible(i915, &unlock, 5000))
> +	if (!shrinker_lock(i915, 0, &unlock))
>   		return NOTIFY_DONE;
>   
>   	/* Force everything onto the inactive lists */
> -	ret = i915_gem_wait_for_idle(i915,
> -				     I915_WAIT_LOCKED,
> -				     MAX_SCHEDULE_TIMEOUT);
> -	if (ret)
> +	if (i915_gem_wait_for_idle(i915,
> +				   I915_WAIT_LOCKED,
> +				   MAX_SCHEDULE_TIMEOUT))
>   		goto out;
>   
>   	intel_runtime_pm_get(i915);
> 

Regards,

Tvrtko