On Mon, Feb 20, 2012 at 04:13:46PM +0000, Dave Airlie wrote:
From: Dave Airlie airlied@redhat.com
a step towards correct hot unplug for USB devices, we need to remove the userspace facing bits at the unplug time for correct udev operation.
Signed-off-by: Dave Airlie airlied@redhat.com
The lack of any WARN_ON(mutex_is_locked) here and the funny comment about the sysfs vs. hotunplug deadlock in the next patch makes me a bit uneasy.
I think the only issue race we need to care about here is a hotremove vs. module unload race. Everything else should stay around for long enough (although this might not quite be true with the current code ...). Simply add a dev->hotremove_mutex and grabbing it in these two functions should fix this.
It's a bit a funky locking scheme, but imo it should keep on working even when properly fix up all our setup/teardown issues: - setup just needs to properly order ctors, i.e. publish the userspace interfaces only after everything is properly set up - we don't need any locking to achieve that (well, currently we still rely massively on the global_mutex dutcttape). - concurrent removal of the userspace interfaces (like here) would be protected by the new hotremove_mutex lock. - protection against the underlying device disappearing would be handled by dev->unplugged (I have some more comments about that) - and the actual drm_device teardown controlled by reference-counting. Currently we get away with abusing the fd open count, but I think sooner or later we want a real reference count (e.g. when exporting buffers with dma_buf we can't just reap them when the last user disappears).
Cheers, Daniel
drivers/gpu/drm/drm_sysfs.c | 7 ++++++- 1 files changed, 6 insertions(+), 1 deletions(-)
diff --git a/drivers/gpu/drm/drm_sysfs.c b/drivers/gpu/drm/drm_sysfs.c index 62c3675..5a7bd51 100644 --- a/drivers/gpu/drm/drm_sysfs.c +++ b/drivers/gpu/drm/drm_sysfs.c @@ -454,6 +454,8 @@ void drm_sysfs_connector_remove(struct drm_connector *connector) { int i;
- if (!connector->kdev.parent)
return;@@ -461,6 +463,7 @@ void drm_sysfs_connector_remove(struct drm_connector *connector) device_remove_file(&connector->kdev, &connector_attrs[i]); sysfs_remove_bin_file(&connector->kdev.kobj, &edid_attr); device_unregister(&connector->kdev);
- connector->kdev.parent = NULL;
} EXPORT_SYMBOL(drm_sysfs_connector_remove);
@@ -533,7 +536,9 @@ err_out: */ void drm_sysfs_device_remove(struct drm_minor *minor) {
- device_unregister(&minor->kdev);
- if (minor->kdev.parent)
device_unregister(&minor->kdev);- minor->kdev.parent = NULL;
}
-- 1.7.6
dri-devel mailing list dri-devel@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/dri-devel