Commit d5eb3a74 authored by Ian Abbott's avatar Ian Abbott Committed by Greg Kroah-Hartman

staging: comedi: don't use mutex when polling file

The main mutex in a comedi device can get held for quite a while when
processing comedi instructions, so for performance reasons, the "read"
and "write" file operations do not use it; they use use the
`attach_lock` rwsemaphore to protect against the comedi device becoming
detached at an inopportune moment.  Do the same for the "poll" file
operation.
Signed-off-by: default avatarIan Abbott <abbotti@mev.co.uk>
Reviewed-by: default avatarH Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 3834234f
...@@ -2264,7 +2264,7 @@ static unsigned int comedi_poll(struct file *file, poll_table *wait) ...@@ -2264,7 +2264,7 @@ static unsigned int comedi_poll(struct file *file, poll_table *wait)
struct comedi_device *dev = cfp->dev; struct comedi_device *dev = cfp->dev;
struct comedi_subdevice *s, *s_read; struct comedi_subdevice *s, *s_read;
mutex_lock(&dev->mutex); down_read(&dev->attach_lock);
if (!dev->attached) { if (!dev->attached) {
dev_dbg(dev->class_dev, "no driver attached\n"); dev_dbg(dev->class_dev, "no driver attached\n");
...@@ -2294,7 +2294,7 @@ static unsigned int comedi_poll(struct file *file, poll_table *wait) ...@@ -2294,7 +2294,7 @@ static unsigned int comedi_poll(struct file *file, poll_table *wait)
} }
done: done:
mutex_unlock(&dev->mutex); up_read(&dev->attach_lock);
return mask; return mask;
} }
......
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