Fix a scheduling while atomic BUG by setting low_latency to 0.
The low_latency flag determines the amount of latency the
data transfer is allowed.
This bug occurs since functions such as mutex_lock() which
can sleep are used with low_latency set(interrupt context).
The fix removes low_latency flag from u_serial.c and hence
prevents the BUG.
Tested on OMAP4430 SDP.
Signed-off-by: Maulik Mankad <x0082077@xxxxxx>
Cc: David Brownell <david-b@xxxxxxxxxxx>
---
Based on 2.6.35-rc3
Index: mainline/drivers/usb/gadget/u_serial.c
===================================================================
--- mainline.orig/drivers/usb/gadget/u_serial.c
+++ mainline/drivers/usb/gadget/u_serial.c
@@ -536,9 +536,6 @@ recycle:
list_move(&req->list, &port->read_pool);
}
- /* Push from tty to ldisc; this is immediate with low_latency, and
- * may trigger callbacks to this driver ... so drop the spinlock.
- */
if (tty && do_push) {
spin_unlock_irq(&port->port_lock);
tty_flip_buffer_push(tty);
@@ -784,11 +781,6 @@ static int gs_open(struct tty_struct *tt
port->open_count = 1;
port->openclose = false;
- /* low_latency means ldiscs work in tasklet context, without
- * needing a workqueue schedule ... easier to keep up.
- */
- tty->low_latency = 1;
-
/* if connected, start the I/O stream */
if (port->port_usb) {
struct gserial *gser = port->port_usb;
--
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