On Wed, Jul 23, 2014 at 05:26:46PM +0200, David Herrmann wrote:
> Instead of allocating the minor-index during registration, we now do this
> during allocation. This way, debug-messages between minor-allocation and
> minor-registration will now use the correct minor instead of 0. Same is
> done for unregistration vs. free, so debug-messages between
> device-shutdown and device-destruction show proper indices.
>
> Even though minor-indices are allocated early, we don't enable minor
> lookup early. Instead, we keep the entry set to NULL and replace it during
> registration / unregistration. This way, the index is allocated but lookup
> only works if registered.
>
> Signed-off-by: David Herrmann <dh.herrmann at gmail.com>
> ---
> drivers/gpu/drm/drm_stub.c | 84
> +++++++++++++++++++++++++---------------------
> 1 file changed, 46 insertions(+), 38 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_stub.c b/drivers/gpu/drm/drm_stub.c
> index b249f14..8b24db5 100644
> --- a/drivers/gpu/drm/drm_stub.c
> +++ b/drivers/gpu/drm/drm_stub.c
> @@ -256,6 +256,8 @@ static struct drm_minor **drm_minor_get_slot(struct
> drm_device *dev,
> static int drm_minor_alloc(struct drm_device *dev, unsigned int type)
> {
> struct drm_minor *minor;
> + unsigned long flags;
> + int r;
>
> minor = kzalloc(sizeof(*minor), GFP_KERNEL);
> if (!minor)
> @@ -264,57 +266,68 @@ static int drm_minor_alloc(struct drm_device *dev,
> unsigned int type)
> minor->type = type;
> minor->dev = dev;
>
> + idr_preload(GFP_KERNEL);
> + spin_lock_irqsave(&drm_minor_lock, flags);
> + r = idr_alloc(&drm_minors_idr,
> + NULL,
> + 64 * type,
> + 64 * (type + 1),
> + GFP_NOWAIT);
> + spin_unlock_irqrestore(&drm_minor_lock, flags);
> + idr_preload_end();
> +
> + if (r < 0)
> + goto err_free;
> +
> + minor->index = r;
> +
> *drm_minor_get_slot(dev, type) = minor;
> return 0;
> +
> +err_free:
> + kfree(minor);
> + return r;
> }
>
> static void drm_minor_free(struct drm_device *dev, unsigned int type)
> {
> - struct drm_minor **slot;
> + struct drm_minor **slot, *minor;
> + unsigned long flags;
>
> slot = drm_minor_get_slot(dev, type);
> - if (*slot) {
> - drm_mode_group_destroy(&(*slot)->mode_group);
> - kfree(*slot);
> - *slot = NULL;
> - }
> + minor = *slot;
> + if (!minor)
> + return;
> +
> + drm_mode_group_destroy(&minor->mode_group);
> +
> + spin_lock_irqsave(&drm_minor_lock, flags);
> + idr_remove(&drm_minors_idr, minor->index);
> + spin_unlock_irqrestore(&drm_minor_lock, flags);
I don't understand why you do the idr removal in stages too. Otherwise
this looks good.
Aside: If two drivers load concurrently (i.e. in the brave new world
withou drm_global_mutex) we might end up with interleaved minor ids. Dunno
whether we'll care since userspace should use udev/sysfs lookups anyway.
igt sometimes doesn't ;-)
> +
> + kfree(minor);
> + *slot = NULL;
> }
>
> static int drm_minor_register(struct drm_device *dev, unsigned int type)
> {
> - struct drm_minor *new_minor;
> + struct drm_minor *minor;
> unsigned long flags;
> int ret;
> - int minor_id;
>
> DRM_DEBUG("\n");
>
> - new_minor = *drm_minor_get_slot(dev, type);
> - if (!new_minor)
> + minor = *drm_minor_get_slot(dev, type);
> + if (!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_NOWAIT);
> - spin_unlock_irqrestore(&drm_minor_lock, flags);
> - idr_preload_end();
> -
> - if (minor_id < 0)
> - return minor_id;
> -
> - new_minor->index = minor_id;
> -
> - ret = drm_debugfs_init(new_minor, minor_id, drm_debugfs_root);
> + ret = drm_debugfs_init(minor, minor->index, drm_debugfs_root);
> if (ret) {
> DRM_ERROR("DRM: Failed to initialize /sys/kernel/debug/dri.\n");
> - goto err_id;
> + return ret;
> }
>
> - ret = drm_sysfs_device_add(new_minor);
> + ret = drm_sysfs_device_add(minor);
> if (ret) {
> DRM_ERROR("DRM: Error sysfs_device_add.\n");
> goto err_debugfs;
> @@ -322,19 +335,14 @@ static int drm_minor_register(struct drm_device *dev,
> unsigned int type)
>
> /* 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);
> + idr_replace(&drm_minors_idr, minor, minor->index);
> spin_unlock_irqrestore(&drm_minor_lock, flags);
>
> - DRM_DEBUG("new minor assigned %d\n", minor_id);
> + DRM_DEBUG("new minor registered %d\n", minor->index);
> 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;
> + drm_debugfs_cleanup(minor);
> return ret;
> }
>
> @@ -347,10 +355,10 @@ static void drm_minor_unregister(struct drm_device
> *dev, unsigned int type)
> if (!minor || !minor->kdev)
> return;
>
> + /* replace @minor with NULL so lookups will fail from now on */
> spin_lock_irqsave(&drm_minor_lock, flags);
> - idr_remove(&drm_minors_idr, minor->index);
> + idr_replace(&drm_minors_idr, NULL, minor->index);
> spin_unlock_irqrestore(&drm_minor_lock, flags);
> - minor->index = 0;
>
> drm_debugfs_cleanup(minor);
> drm_sysfs_device_remove(minor);
> --
> 2.0.2
>
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
