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staging: comedi: use attach_lock semaphore during attach and detach 

Acquire the `attach_lock` semaphore in the `struct comedi_device` while
modifying the `attached` flag.  This is a "write" acquire.  Note that
the main mutex in the `struct comedi_device` is also held at this time.
Tasks wishing to check the device is attached will need to either
acquire the main mutex, or "read" acquire the `attach_lock` semaphore,
or both in that order.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ian Abbott 2013-11-08 15:03:25 +00:00 committed by Greg Kroah-Hartman
parent 2f3fdcd7ce
commit bf11c13424
1 changed files with 4 additions and 1 deletions
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5
drivers/staging/comedi/drivers.c
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@ -133,10 +133,12 @@ static void cleanup_device(struct comedi_device *dev)
void comedi_device_detach(struct comedi_device *dev)
{
down_write(&dev->attach_lock);
dev->attached = false;
if (dev->driver)
dev->driver->detach(dev);
cleanup_device(dev);
up_write(&dev->attach_lock);
}
static int poll_invalid(struct comedi_device *dev, struct comedi_subdevice *s)
@ -355,8 +357,9 @@ static int comedi_device_postconfig(struct comedi_device *dev)
ret = __comedi_device_postconfig(dev);
if (ret < 0)
return ret;
smp_wmb();
down_write(&dev->attach_lock);
dev->attached = true;
up_write(&dev->attach_lock);
return 0;
}