From 3834234f99a07d1a84918cb15e9431420c5405f4 Mon Sep 17 00:00:00 2001
From: Ian Abbott <abbotti@mev.co.uk>
Date: Fri, 9 Oct 2015 12:26:51 +0100
Subject: [PATCH] staging: comedi: check command started by file being polled
Currently, the "poll" file operation checks if an asynchronous "read"
(or "write" command is active on the "read" (or "write" subdevice, but
does not consider whether the command was started from the file object
being polled. Since that is the only file object able to read (or
write) data, take it into consideration.
With this change, if no read (or write) command is running on the
subdevice, or it is started by a different file object, the file object
is marked as readable (or writeable) regardless, but the read (or write)
file operation will return an error.
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 | 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 42f6971c8061d..1d6bef2858212 100644
--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -2275,7 +2275,7 @@ static unsigned int comedi_poll(struct file *file, poll_table *wait)
s_read = s;
if (s && s->async) {
poll_wait(file, &s->async->wait_head, wait);
- if (!s->busy || !comedi_is_subdevice_running(s) ||
+ if (s->busy != file || !comedi_is_subdevice_running(s) ||
(s->async->cmd.flags & CMDF_WRITE) ||
comedi_buf_read_n_available(s) > 0)
mask |= POLLIN | POLLRDNORM;
@@ -2287,7 +2287,7 @@ static unsigned int comedi_poll(struct file *file, poll_table *wait)
if (s != s_read)
poll_wait(file, &s->async->wait_head, wait);
- if (!s->busy || !comedi_is_subdevice_running(s) ||
+ if (s->busy != file || !comedi_is_subdevice_running(s) ||
!(s->async->cmd.flags & CMDF_WRITE) ||
comedi_buf_write_n_available(s) >= bps)
mask |= POLLOUT | POLLWRNORM;
--
2.30.2