From ecf04ed34d65b735bbdfa9ae8ea378ffc0faa9f6 Mon Sep 17 00:00:00 2001 From: Ian Abbott Date: Fri, 9 Oct 2015 12:26:50 +0100 Subject: [PATCH] staging: comedi: don't allocate buffer space when polling for write 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 Reviewed-by: H Hartley Sweeten Signed-off-by: Greg Kroah-Hartman --- 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 bd124815c06a..42f6971c8061 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; }