drm/i915/shrinker: Wait before acquiring struct_mutex under oom

We can now wait for the GPU (all engines) to become idle without
requiring the struct_mutex. Inside the shrinker, we need to currently
take the struct_mutex in order to purge objects and to purge the objects
we need the GPU to be idle - causing a stall whilst we hold the
struct_mutex. We can hide most of that stall by performing the wait
before taking the struct_mutex and only doing essential waits for
new rendering on objects to be freed.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470388464-28458-8-git-send-email-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/i915_gem_shrinker.c b/drivers/gpu/drm/i915/i915_gem_shrinker.c
index 23d7037..9b92b64 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_shrinker.c
+++ b/drivers/gpu/drm/i915/i915_gem_shrinker.c
@@ -323,17 +323,22 @@ i915_gem_shrinker_lock_uninterruptible(struct drm_i915_private *dev_priv,
                                       struct shrinker_lock_uninterruptible *slu,
                                       int timeout_ms)
 {
-       unsigned long timeout = msecs_to_jiffies(timeout_ms) + 1;
+       unsigned long timeout = jiffies + msecs_to_jiffies_timeout(timeout_ms);
+
+       do {
+               if (i915_gem_wait_for_idle(dev_priv, false) == 0 &&
+                   i915_gem_shrinker_lock(&dev_priv->drm, &slu->unlock))
+                       break;
 
-       while (!i915_gem_shrinker_lock(&dev_priv->drm, &slu->unlock)) {
                schedule_timeout_killable(1);
                if (fatal_signal_pending(current))
                        return false;
-               if (--timeout == 0) {
+
+               if (time_after(jiffies, timeout)) {
                        pr_err("Unable to lock GPU to purge memory.\n");
                        return false;
                }
-       }
+       } while (1);
 
        slu->was_interruptible = dev_priv->mm.interruptible;
        dev_priv->mm.interruptible = false;