usb: cdc-acm: drain writes on close
Add a mechanism to let the write queue drain naturally before
closing the TTY, rather than always losing that data. There
is a timeout, so it can't wait too long.
Provide missing locking inside acm_wb_is_avail(); it matters
more now. Note, this presumes an earlier patch was applied,
removing a call to this routine where the lock was held.
Slightly improved diagnostics on write URB completion, so we
can tell when a write URB gets killed and, if so, how much
data it wrote first ... and so that I/O path is normally
silent (and can't much change timings).
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/usb/class/cdc-acm.h b/drivers/usb/class/cdc-acm.h
index 9426636..1f95e7a 100644
--- a/drivers/usb/class/cdc-acm.h
+++ b/drivers/usb/class/cdc-acm.h
@@ -113,6 +113,7 @@
struct usb_cdc_line_coding line; /* bits, stop, parity */
struct work_struct work; /* work queue entry for line discipline waking up */
struct work_struct waker;
+ wait_queue_head_t drain_wait; /* close processing */
struct tasklet_struct urb_task; /* rx processing */
spinlock_t throttle_lock; /* synchronize throtteling and read callback */
unsigned int ctrlin; /* input control lines (DCD, DSR, RI, break, overruns) */