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[media] V4L: improve the BKL replacement heuristic

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The BKL replacement mutex had some serious performance side-effects on
V4L drivers. It is replaced by a better heuristic that works around the
worst of the side-effects.

Read the v4l2-dev.c comments for the whole sorry story. This is a
temporary measure only until we can convert all v4l drivers to use
unlocked_ioctl.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
This commit is contained in:
Hans Verkuil
2010-11-26 06:47:28 -03:00
committed by Mauro Carvalho Chehab
parent 2877842de8
commit 879aa24d63
3 changed files with 31 additions and 3 deletions
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2
include/media/v4l2-device.h
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@ -51,6 +51,8 @@ struct v4l2_device {
unsigned int notification, void *arg);
/* The control handler. May be NULL. */
struct v4l2_ctrl_handler *ctrl_handler;
/* BKL replacement mutex. Temporary solution only. */
struct mutex ioctl_lock;
};
/* Initialize v4l2_dev and make dev->driver_data point to v4l2_dev.