drm/i915: Removing polling for struct_mutex from vmap shrinker

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.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190109164204.23935-2-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 8ad9519..6cc2b96 100644 (file)
--- 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);