staging: comedi: don't use mutex when polling file
authorIan Abbott <abbotti@mev.co.uk>
Fri, 9 Oct 2015 11:26:52 +0000 (12:26 +0100)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Tue, 13 Oct 2015 17:28:40 +0000 (10:28 -0700)
commitd5eb3a742109015cd794e536fe0968197b917e05
tree1026682877418570aaea093af554b84b9e5d37a4
parent3834234f99a07d1a84918cb15e9431420c5405f4
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: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/staging/comedi/comedi_fops.c