drm/i915/perf: ensure we keep a reference on the driver

The i915 perf stream has its own file descriptor and is tied to
reference of the driver. We haven't taken care of keep the driver
alive.

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Suggested-by: Chris Wilson <chris@chris-wilson.co.uk>
Fixes: eec688e1420da5 ("drm/i915: Add i915 perf infrastructure")
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190709123351.5645-2-lionel.g.landwerlin@intel.com
(cherry picked from commit a5af1df716c123a09341351008fc497bea137b77)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c
index 1ae06a1..629511e 100644 (file)
--- a/drivers/gpu/drm/i915/i915_perf.c
+++ b/drivers/gpu/drm/i915/i915_perf.c
@@ -2515,6 +2515,9 @@ static int i915_perf_release(struct inode *inode, struct file *file)
        i915_perf_destroy_locked(stream);
        mutex_unlock(&dev_priv->perf.lock);
 
+       /* Release the reference the perf stream kept on the driver. */
+       drm_dev_put(&dev_priv->drm);
+
        return 0;
 }
 
@@ -2650,6 +2653,11 @@ i915_perf_open_ioctl_locked(struct drm_i915_private *dev_priv,
        if (!(param->flags & I915_PERF_FLAG_DISABLED))
                i915_perf_enable_locked(stream);
 
+       /* Take a reference on the driver that will be kept with stream_fd
+        * until its release.
+        */
+       drm_dev_get(&dev_priv->drm);
+
        return stream_fd;
 
 err_open: