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 <[email protected]> --- 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 _______________________________________________ devel mailing list [email protected] http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
