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: Ian Abbott <abbotti@xxxxxxxxx>
---
drivers/staging/comedi/comedi_fops.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
index 07bb197..88e9334 100644
--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -2264,7 +2264,7 @@ static unsigned int comedi_poll(struct file *file, poll_table *wait)
struct comedi_device *dev = cfp->dev;
struct comedi_subdevice *s, *s_read;
- mutex_lock(&dev->mutex);
+ down_read(&dev->attach_lock);
if (!dev->attached) {
dev_dbg(dev->class_dev, "no driver attached\n");
@@ -2294,7 +2294,7 @@ static unsigned int comedi_poll(struct file *file, poll_table *wait)
}
done:
- mutex_unlock(&dev->mutex);
+ up_read(&dev->attach_lock);
return mask;
}
--
2.6.1
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