drm/i915: Handle error paths during watermark sanitization properly (v3)

sanitize_watermarks() does not properly handle errors returned by
drm_atomic_helper_duplicate_state().  Make failures drop locks before
returning.  We also change the lock of connection_mutex to a
drm_modeset_lock_all_ctx() to make sure any EDEADLK's are handled
earlier.

v2: Change call to lock connetion_mutex with a call to
    drm_modeset_lock_all_ctx().  This ensures that any lock contention
    is handled earlier and drm_atomic_helper_duplicate_state() won't
    return EDEADLK. (Maarten)

v3: Drop locks properly in more error paths. (Maarten)

Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1452611617-32144-1-git-send-email-matthew.d.roper@intel.com

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 9c87d5784f1a8b4bb66a7568fdf79a03db0f0625..3b79981735c81cca7b0170de2d4e99128ff06240 100644 (file)
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -15355,17 +15355,17 @@ static void sanitize_watermarks(struct drm_device *dev)
         */
        drm_modeset_acquire_init(&ctx, 0);
 retry:
-       ret = drm_modeset_lock(&dev->mode_config.connection_mutex, &ctx);
+       ret = drm_modeset_lock_all_ctx(dev, &ctx);
        if (ret == -EDEADLK) {
                drm_modeset_backoff(&ctx);
                goto retry;
        } else if (WARN_ON(ret)) {
-               return;
+               goto fail;
        }
 
        state = drm_atomic_helper_duplicate_state(dev, &ctx);
        if (WARN_ON(IS_ERR(state)))
-               return;
+               goto fail;
 
        /*
         * Hardware readout is the only time we don't want to calculate
@@ -15388,7 +15388,7 @@ static void sanitize_watermarks(struct drm_device *dev)
                 * BIOS-programmed watermarks untouched and hope for the best.
                 */
                WARN(true, "Could not determine valid watermarks for inherited state\n");
-               return;
+               goto fail;
        }
 
        /* Write calculated watermark values back */
@@ -15401,6 +15401,7 @@ static void sanitize_watermarks(struct drm_device *dev)
        }
 
        drm_atomic_state_free(state);
+fail:
        drm_modeset_drop_locks(&ctx);
        drm_modeset_acquire_fini(&ctx);
 }