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authorDavid Herrmann <dh.herrmann@gmail.com>2014-02-24 15:53:25 +0100
committerDavid Herrmann <dh.herrmann@gmail.com>2014-03-16 12:54:21 +0100
commit0d639883ee26359e1bf38195df1dbca0f879e239 (patch)
tree6ff7b2284957af9efb3b7a3df3395d75c18cb366 /drivers/gpu/drm/drm_stub.c
parent7d86cf1a4fc0c0bdb6947185c6fe71301dfea7b1 (diff)
downloadlinux-0d639883ee26359e1bf38195df1dbca0f879e239.tar.bz2
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: David Herrmann <dh.herrmann@gmail.com>
Diffstat (limited to 'drivers/gpu/drm/drm_stub.c')
-rw-r--r--drivers/gpu/drm/drm_stub.c51
1 files changed, 45 insertions, 6 deletions
diff --git a/drivers/gpu/drm/drm_stub.c b/drivers/gpu/drm/drm_stub.c
index 83ef4a63358c..c23eaf6442ff 100644
--- a/drivers/gpu/drm/drm_stub.c
+++ b/drivers/gpu/drm/drm_stub.c
@@ -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;
}