From: Daniel Vetter <daniel.vetter@ffwll.ch>
Date: Tue, 4 Jul 2017 15:18:25 +0000 (+0200)
Subject: drm/fb-helper: Drop locking from the vsync wait ioctl code
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=235d3e4fa115b39a72112f29ec5c84b847111edd;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git

drm/fb-helper: Drop locking from the vsync wait ioctl code

Like with the drm-native vblank wait ioctl we can entirely rely on the
spinlocks in drm_vblank.c, no need at all to take expensive mutexes.
The only reason we had to take mode_config.mutex was to protect the
fbdev helper's data-structures, but that's now done by
fb_helper->lock.

Cc: John Stultz <john.stultz@linaro.org>
Cc: Thierry Reding <treding@nvidia.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170704151833.17304-6-daniel.vetter@ffwll.ch
---

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 08a5e0d23a42..9efb17c3cbe8 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -1328,7 +1328,6 @@ int drm_fb_helper_ioctl(struct fb_info *info, unsigned int cmd,
 		goto unlock;
 	}
 
-	mutex_lock(&dev->mode_config.mutex);
 	switch (cmd) {
 	case FBIO_WAITFORVSYNC:
 		/*
@@ -1368,7 +1367,6 @@ int drm_fb_helper_ioctl(struct fb_info *info, unsigned int cmd,
 	}
 
 unlock:
-	mutex_unlock(&dev->mode_config.mutex);
 	mutex_unlock(&fb_helper->lock);
 	return ret;
 }