When handling the "poll" file operation and checking for `POLLOUT`, don't allocate space from the buffer for writing, just check that space is available for writing. That check is done after checking that an asynchronous "write" command is running on the subdevice. Allocating the buffer space before checking a "write" command is running can cause problems if the subdevice supports commands in either direction and currently has an active "read" command.
Signed-off-by: Ian Abbott <abbo...@mev.co.uk> --- drivers/staging/comedi/comedi_fops.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c index 9dcd486..4793e30 100644 --- a/drivers/staging/comedi/comedi_fops.c +++ b/drivers/staging/comedi/comedi_fops.c @@ -2287,10 +2287,9 @@ static unsigned int comedi_poll(struct file *file, poll_table *wait) if (s != s_read) poll_wait(file, &s->async->wait_head, wait); - comedi_buf_write_alloc(s, s->async->prealloc_bufsz); if (!s->busy || !comedi_is_subdevice_running(s) || !(s->async->cmd.flags & CMDF_WRITE) || - comedi_buf_write_n_allocated(s) >= bps) + comedi_buf_write_n_available(s) >= bps) mask |= POLLOUT | POLLWRNORM; } -- 2.6.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/