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@xxxxxxxxx>
---
drivers/staging/comedi/drivers.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/drivers/staging/comedi/drivers.c b/drivers/staging/comedi/drivers.c
index 8f02bf6..c398422 100644
--- a/drivers/staging/comedi/drivers.c
+++ b/drivers/staging/comedi/drivers.c
@@ -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;
}
--
1.8.4.2
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