[PATCH] drm: fix another race due to BKL removal.

[Dave Airlie]

From: Dave Airlie <airlied at redhat.com>

Since module loading was happening under the BKL, and the drm open path took
the BKL you couldn't race between them. The drm adds the sysfs node before it
really probably should, i.e. before driver load has completed. Then udev
creates the device node, and plymouth opens the device before we've completed
loading the driver. This results in fail.

Fix this now by taking the global mutex around the driver loading procedure,
which seems like the lesser of two evils patch to fix the regression.

Reported-by: Toni Spets (hifi on #radeon)
Cc: Arnd Bergmann <arnd at arndb.de>
Signed-off-by: Dave Airlie <airlied at redhat.com>
---
 drivers/gpu/drm/drm_pci.c      |    4 ++++
 drivers/gpu/drm/drm_platform.c |    5 +++++
 2 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/drivers/gpu/drm/drm_pci.c b/drivers/gpu/drm/drm_pci.c
index e20f78b..f5bd9e5 100644
--- a/drivers/gpu/drm/drm_pci.c
+++ b/drivers/gpu/drm/drm_pci.c
@@ -164,6 +164,8 @@ int drm_get_pci_dev(struct pci_dev *pdev, const struct pci_device_id *ent,
 	dev->hose = pdev->sysdata;
 #endif
 
+	mutex_lock(&drm_global_mutex);
+
 	if ((ret = drm_fill_in_dev(dev, ent, driver))) {
 		printk(KERN_ERR "DRM: Fill_in_dev failed.\n");
 		goto err_g2;
@@ -199,6 +201,7 @@ int drm_get_pci_dev(struct pci_dev *pdev, const struct pci_device_id *ent,
 		 driver->name, driver->major, driver->minor, driver->patchlevel,
 		 driver->date, pci_name(pdev), dev->primary->index);
 
+	mutex_unlock(&drm_global_mutex);
 	return 0;
 
 err_g4:
@@ -210,6 +213,7 @@ err_g2:
 	pci_disable_device(pdev);
 err_g1:
 	kfree(dev);
+	mutex_unlock(&drm_global_mutex);
 	return ret;
 }
 EXPORT_SYMBOL(drm_get_pci_dev);
diff --git a/drivers/gpu/drm/drm_platform.c b/drivers/gpu/drm/drm_platform.c
index 460e9a3..92d1d0f 100644
--- a/drivers/gpu/drm/drm_platform.c
+++ b/drivers/gpu/drm/drm_platform.c
@@ -53,6 +53,8 @@ int drm_get_platform_dev(struct platform_device *platdev,
 	dev->platformdev = platdev;
 	dev->dev = &platdev->dev;
 
+	mutex_lock(&drm_global_mutex);
+
 	ret = drm_fill_in_dev(dev, NULL, driver);
 
 	if (ret) {
@@ -87,6 +89,8 @@ int drm_get_platform_dev(struct platform_device *platdev,
 
 	list_add_tail(&dev->driver_item, &driver->device_list);
 
+	mutex_unlock(&drm_global_mutex);
+
 	DRM_INFO("Initialized %s %d.%d.%d %s on minor %d\n",
 		 driver->name, driver->major, driver->minor, driver->patchlevel,
 		 driver->date, dev->primary->index);
@@ -100,6 +104,7 @@ err_g2:
 		drm_put_minor(&dev->control);
 err_g1:
 	kfree(dev);
+	mutex_unlock(&drm_global_mutex);
 	return ret;
 }
 EXPORT_SYMBOL(drm_get_platform_dev);
-- 
1.7.2.2