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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>
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1 changed files with 4 additions and 1 deletions
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@ -133,10 +133,12 @@ static void cleanup_device(struct comedi_device *dev)
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void comedi_device_detach(struct comedi_device *dev)
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{
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down_write(&dev->attach_lock);
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dev->attached = false;
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if (dev->driver)
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dev->driver->detach(dev);
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cleanup_device(dev);
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up_write(&dev->attach_lock);
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}
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static int poll_invalid(struct comedi_device *dev, struct comedi_subdevice *s)
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@ -355,8 +357,9 @@ static int comedi_device_postconfig(struct comedi_device *dev)
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ret = __comedi_device_postconfig(dev);
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if (ret < 0)
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return ret;
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smp_wmb();
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down_write(&dev->attach_lock);
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dev->attached = true;
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up_write(&dev->attach_lock);
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return 0;
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}
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