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[media] v4l2-dev.h: add comment not to use V4L2_FL_LOCK_ALL_FOPS in new drivers

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This flag is for legacy drivers only and will go away in the future.

A note regarding commit 5126f2590b
(v4l2-dev: add flag to have the core lock all file operations):

That commit message suggests that by not taking the core lock for fops
other than unlocked_ioctl all problems relating to AB-BA locking and
mm->mmap_sem are solved. This is not the case.

More work needs to be done by moving the core lock further down into
video_ioctl2. It should only be taken after the copy_from/to_user calls
are done.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
This commit is contained in:
Hans Verkuil 2012-05-14 11:28:44 -03:00 committed by Mauro Carvalho Chehab
parent 74f22c4864
commit 47bd4bc1a2
1 changed files with 1 additions and 1 deletions
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include/media/v4l2-dev.h
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@ -40,7 +40,7 @@ struct v4l2_ctrl_handler;
/* Use the prio field of v4l2_fh for core priority checking */
#define V4L2_FL_USE_FH_PRIO (2)
/* If ioctl core locking is in use, then apply that also to all
file operations. */
file operations. Don't use this flag in new drivers! */
#define V4L2_FL_LOCK_ALL_FOPS (3)
/* Priority helper functions */