linux-kernel - [PATCH] drm: Fixup hang when unregistering drm dev with open

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Message-Id: <1491944274-29007-1-git-send-email-jeffy.chen@rock-chips.com>
Date:   Wed, 12 Apr 2017 04:57:54 +0800
From:   Jeffy Chen <jeffy.chen@...k-chips.com>
To:     linux-kernel@...r.kernel.org
Cc:     briannorris@...omium.org, dianders@...omium.org,
        tfiga@...omium.org, seanpaul@...omium.org, zyw@...k-chips.com,
        marcheu@...omium.org, mark.yao@...k-chips.com, hshi@...omium.org,
        Jeffy Chen <jeffy.chen@...k-chips.com>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        dri-devel@...ts.freedesktop.org, David Airlie <airlied@...ux.ie>
Subject: [PATCH] drm: Fixup hang when unregistering drm dev with open_count 0

My previous patch (c5d8fac2bf  drm: Unplug drm device when unregistering
it) calls drm_unplug_dev when unregistering drm dev. But if open_count
is 0, the unplug will try to unregister the drm dev again and cause
deadlock.

Fix it by dropping drm_unplug_dev and use drm_device_set_plug_state
directly.

Signed-off-by: Jeffy Chen <jeffy.chen@...k-chips.com>

---

 drivers/gpu/drm/drm_drv.c | 15 +--------------
 include/drm/drm_drv.h     |  1 -
 2 files changed, 1 insertion(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index ad13e20..cc2d018 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -355,19 +355,6 @@ void drm_put_dev(struct drm_device *dev)
 }
 EXPORT_SYMBOL(drm_put_dev);
 
-void drm_unplug_dev(struct drm_device *dev)
-{
-	mutex_lock(&drm_global_mutex);
-
-	drm_device_set_plug_state(dev, false);
-
-	if (dev->open_count == 0) {
-		drm_put_dev(dev);
-	}
-	mutex_unlock(&drm_global_mutex);
-}
-EXPORT_SYMBOL(drm_unplug_dev);
-
 /*
  * DRM internal mount
  * We want to be able to allocate our own "struct address_space" to control
@@ -825,7 +812,7 @@ void drm_dev_unregister(struct drm_device *dev)
 	drm_lastclose(dev);
 
 	dev->registered = false;
-	drm_unplug_dev(dev);
+	drm_device_set_plug_state(dev, false);
 
 	if (drm_core_check_feature(dev, DRIVER_MODESET))
 		drm_modeset_unregister_all(dev);
diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
index 0fefc3f..eb63078 100644
--- a/include/drm/drm_drv.h
+++ b/include/drm/drm_drv.h
@@ -544,7 +544,6 @@ void drm_dev_unregister(struct drm_device *dev);
 void drm_dev_ref(struct drm_device *dev);
 void drm_dev_unref(struct drm_device *dev);
 void drm_put_dev(struct drm_device *dev);
-void drm_unplug_dev(struct drm_device *dev);
 
 int drm_dev_set_unique(struct drm_device *dev, const char *name);
 
-- 
2.1.4