Re: [PATCH] drm: Release filp before global lock

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Hi, Chris,

On 1/22/20 4:56 PM, Chris Wilson wrote:
The file is not part of the global drm resource and can be released
prior to take the global mutex to drop the open_count (and potentially
close) the drm device.

However, inside drm_close_helper() there are a number of dev->driver
callbacks that take the drm_device as the first parameter... Worryingly
some of those callbacks may be (implicitly) depending on the global
mutex.

I read this as you suspect that there are driver callbacks inside drm_close_helper() that might need the global mutex held? But then it wouldn't be safe to move the lock? Is there a strong motivation for moving the locking in the first place? Also a minor nit below:


Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
  drivers/gpu/drm/drm_file.c | 4 ++--
  1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
index 92d16724f949..84ed313ee2e9 100644
--- a/drivers/gpu/drm/drm_file.c
+++ b/drivers/gpu/drm/drm_file.c
@@ -438,12 +438,12 @@ int drm_release(struct inode *inode, struct file *filp)
  	struct drm_minor *minor = file_priv->minor;
  	struct drm_device *dev = minor->dev;
- mutex_lock(&drm_global_mutex);
-
  	DRM_DEBUG("open_count = %d\n", dev->open_count);

The read of dev->open_count should still be inside the lock to be consistent with the value that is decremented below. Perhaps move the DRM_DEBUG()?

drm_close_helper(filp); + mutex_lock(&drm_global_mutex);
+
  	if (!--dev->open_count)
  		drm_lastclose(dev);

Thanks,

Thomas


_______________________________________________
dri-devel mailing list
dri-devel@xxxxxxxxxxxxxxxxxxxxx
https://lists.freedesktop.org/mailman/listinfo/dri-devel



[Index of Archives]     [Linux DRI Users]     [Linux Intel Graphics]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]     [XFree86]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Linux Kernel]     [Linux SCSI]     [XFree86]
  Powered by Linux