On 28-05-17 19:10, Hans de Goede wrote:
Since commit a39be606f99d ("drm: Do a full device unregister when
unplugging") drm_unplug_dev has been calling drm_dev_unregister followed
by a drm_put_dev when open_count reaches 0. This drm_put_dev calls
drm_dev_unregister again. Since drm_dev_unregister is not protected
against being called multiple times this leads to havoc.
This commit fixes this by calling drm_dev_unref instead of drm_put_dev.
This commit also moves the mutex_lock(&drm_global_mutex) to above the
drm_dev_unregister call to avoid a race between drm_unplug_dev and
drm_release still leading to drm_dev_unregister getting called twice.
Note that calling drm_dev_unregister with the drm_global_mutex locked is
fine, drm_release already did this (through drm_put_dev).
Ugh I just realized that the whole moving of the mutex thing is not
necessary as I ended up changing the drm_put_dev in drm_release to
drm_dev_unref too. I will send a v2 shortly.
Regards,
Hans
Fixes: a39be606f99d ("drm: Do a full device unregister when unplugging")
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Marco Diego Aurélio Mesquita <marcodiegomesquita@xxxxxxxxx>
Reported-by: Marco Diego Aurélio Mesquita <marcodiegomesquita@xxxxxxxxx>
Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
---
Note I don't have any USB display devices at hand for testing atm so
this patch has only been compile tested.
---
drivers/gpu/drm/drm_drv.c | 10 +++++-----
drivers/gpu/drm/drm_file.c | 2 +-
2 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index b5c6bb46a425..9f31d5d629d1 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -357,16 +357,16 @@ EXPORT_SYMBOL(drm_put_dev);
void drm_unplug_dev(struct drm_device *dev)
{
+ mutex_lock(&drm_global_mutex);
+
/* for a USB device */
drm_dev_unregister(dev);
- mutex_lock(&drm_global_mutex);
-
drm_device_set_unplugged(dev);
- if (dev->open_count == 0) {
- drm_put_dev(dev);
- }
+ if (dev->open_count == 0)
+ drm_dev_unref(dev);
+
mutex_unlock(&drm_global_mutex);
}
EXPORT_SYMBOL(drm_unplug_dev);
diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
index 3783b659cd38..edba71c8ccc3 100644
--- a/drivers/gpu/drm/drm_file.c
+++ b/drivers/gpu/drm/drm_file.c
@@ -424,7 +424,7 @@ int drm_release(struct inode *inode, struct file *filp)
if (!--dev->open_count) {
drm_lastclose(dev);
if (drm_device_is_unplugged(dev))
- drm_put_dev(dev);
+ drm_dev_unref(dev);
}
mutex_unlock(&drm_global_mutex);
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