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Commit 0d639883 authored by David Herrmann's avatar David Herrmann
Browse files

drm: make minors independent of global lock 



We used to protect minor-lookup and setup by the global drm lock. To
continue our attempts of dropping drm_global_mutex, this patch makes the
minor management independent of it. Furthermore, we make it all atomic and
switch to spin-locks instead of a mutex.

Now that minor-lookup is independent, we also move the
"drm_is_unplugged()" test into the minor-lookup path. There is no reason
to ever return a minor for unplugged objects, so keep that logic internal.

Signed-off-by: default avatarDavid Herrmann <dh.herrmann@gmail.com>
parent 7d86cf1a

drivers/gpu/drm/drm_fops.c

+1 −10
Original line number Diff line number Diff line
@@ -39,7 +39,7 @@ 
#include <linux/slab.h>

#include <linux/module.h>



/* from BKL pushdown: note that nothing else serializes idr_find() */

/* from BKL pushdown */

DEFINE_MUTEX(drm_global_mutex);

EXPORT_SYMBOL(drm_global_mutex);
@@ -91,11 +91,6 @@ int drm_open(struct inode *inode, struct file *filp) 
		return PTR_ERR(minor);



	dev = minor->dev;

	if (drm_device_is_unplugged(dev)) {

		retcode = -ENODEV;

		goto err_release;

	}



	if (!dev->open_count++)

		need_setup = 1;

	mutex_lock(&dev->struct_mutex);
@@ -127,7 +122,6 @@ int drm_open(struct inode *inode, struct file *filp) 
	dev->dev_mapping = old_mapping;

	mutex_unlock(&dev->struct_mutex);

	dev->open_count--;

err_release:

	drm_minor_release(minor);

	return retcode;

}
@@ -157,9 +151,6 @@ int drm_stub_open(struct inode *inode, struct file *filp) 
		goto out_unlock;



	dev = minor->dev;

	if (drm_device_is_unplugged(dev))

		goto out_release;



	new_fops = fops_get(dev->driver->fops);

	if (!new_fops)

		goto out_release;

drivers/gpu/drm/drm_stub.c

+45 −6
Original line number Diff line number Diff line
@@ -70,6 +70,7 @@ module_param_named(vblankoffdelay, drm_vblank_offdelay, int, 0600); 
module_param_named(timestamp_precision_usec, drm_timestamp_precision, int, 0600);

module_param_named(timestamp_monotonic, drm_timestamp_monotonic, int, 0600);



static DEFINE_SPINLOCK(drm_minor_lock);

struct idr drm_minors_idr;



struct class *drm_class;
@@ -240,6 +241,19 @@ int drm_dropmaster_ioctl(struct drm_device *dev, void *data, 
	return 0;

}



/*

 * DRM Minors

 * A DRM device can provide several char-dev interfaces on the DRM-Major. Each

 * of them is represented by a drm_minor object. Depending on the capabilities

 * of the device-driver, different interfaces are registered.

 *

 * Minors can be accessed via dev->$minor_name. This pointer is either

 * NULL or a valid drm_minor pointer and stays valid as long as the device is

 * valid. This means, DRM minors have the same life-time as the underlying

 * device. However, this doesn't mean that the minor is active. Minors are

 * registered and unregistered dynamically according to device-state.

 */



static struct drm_minor **drm_minor_get_slot(struct drm_device *dev,

					     unsigned int type)

{
@@ -285,6 +299,7 @@ static void drm_minor_free(struct drm_device *dev, unsigned int type) 
static int drm_minor_register(struct drm_device *dev, unsigned int type)

{

	struct drm_minor *new_minor;

	unsigned long flags;

	int ret;

	int minor_id;
@@ -294,19 +309,21 @@ static int drm_minor_register(struct drm_device *dev, unsigned int type) 
	if (!new_minor)

		return 0;



	idr_preload(GFP_KERNEL);

	spin_lock_irqsave(&drm_minor_lock, flags);

	minor_id = idr_alloc(&drm_minors_idr,

			     NULL,

			     64 * type,

			     64 * (type + 1),

			     GFP_KERNEL);

			     GFP_NOWAIT);

	spin_unlock_irqrestore(&drm_minor_lock, flags);

	idr_preload_end();



	if (minor_id < 0)

		return minor_id;



	new_minor->index = minor_id;



	idr_replace(&drm_minors_idr, new_minor, minor_id);



	ret = drm_debugfs_init(new_minor, minor_id, drm_debugfs_root);

	if (ret) {

		DRM_ERROR("DRM: Failed to initialize /sys/kernel/debug/dri.\n");
@@ -319,27 +336,40 @@ static int drm_minor_register(struct drm_device *dev, unsigned int type) 
		goto err_debugfs;

	}



	/* replace NULL with @minor so lookups will succeed from now on */

	spin_lock_irqsave(&drm_minor_lock, flags);

	idr_replace(&drm_minors_idr, new_minor, new_minor->index);

	spin_unlock_irqrestore(&drm_minor_lock, flags);



	DRM_DEBUG("new minor assigned %d\n", minor_id);

	return 0;



err_debugfs:

	drm_debugfs_cleanup(new_minor);

err_id:

	spin_lock_irqsave(&drm_minor_lock, flags);

	idr_remove(&drm_minors_idr, minor_id);

	spin_unlock_irqrestore(&drm_minor_lock, flags);

	new_minor->index = 0;

	return ret;

}



static void drm_minor_unregister(struct drm_device *dev, unsigned int type)

{

	struct drm_minor *minor;

	unsigned long flags;



	minor = *drm_minor_get_slot(dev, type);

	if (!minor || !minor->kdev)

		return;



	spin_lock_irqsave(&drm_minor_lock, flags);

	idr_remove(&drm_minors_idr, minor->index);

	spin_unlock_irqrestore(&drm_minor_lock, flags);

	minor->index = 0;



	drm_debugfs_cleanup(minor);

	drm_sysfs_device_remove(minor);

	idr_remove(&drm_minors_idr, minor->index);

}



/**
@@ -361,12 +391,21 @@ static void drm_minor_unregister(struct drm_device *dev, unsigned int type) 
struct drm_minor *drm_minor_acquire(unsigned int minor_id)

{

	struct drm_minor *minor;

	unsigned long flags;



	spin_lock_irqsave(&drm_minor_lock, flags);

	minor = idr_find(&drm_minors_idr, minor_id);

	if (!minor)

	if (minor)

		drm_dev_ref(minor->dev);

	spin_unlock_irqrestore(&drm_minor_lock, flags);



	if (!minor) {

		return ERR_PTR(-ENODEV);

	} else if (drm_device_is_unplugged(minor->dev)) {

		drm_dev_unref(minor->dev);

		return ERR_PTR(-ENODEV);

	}



	drm_dev_ref(minor->dev);

	return minor;

}