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cdc-acm: introduce a cool down
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Immediate submission in case of a babbling device can lead
to a busy loop. Introducing a delayed work.

Signed-off-by: Oliver Neukum <oneukum@suse.com>
Cc: stable <stable@vger.kernel.org>
Tested-by: Jonas Karlsson <jonas.karlsson@actia.se>
Link: https://lore.kernel.org/r/20200415151358.32664-2-oneukum@suse.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Oliver Neukum authored and Greg Kroah-Hartman committed Apr 16, 2020
1 parent 0afccd7 commit a4e7279
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Showing 2 changed files with 32 additions and 3 deletions.
30 changes: 28 additions & 2 deletions drivers/usb/class/cdc-acm.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -412,9 +412,12 @@ static void acm_ctrl_irq(struct urb *urb)

exit:
retval = usb_submit_urb(urb, GFP_ATOMIC);
if (retval && retval != -EPERM)
if (retval && retval != -EPERM && retval != -ENODEV)
dev_err(&acm->control->dev,
"%s - usb_submit_urb failed: %d\n", __func__, retval);
else
dev_vdbg(&acm->control->dev,
"control resubmission terminated %d\n", retval);
}

static int acm_submit_read_urb(struct acm *acm, int index, gfp_t mem_flags)
Expand All @@ -430,6 +433,8 @@ static int acm_submit_read_urb(struct acm *acm, int index, gfp_t mem_flags)
dev_err(&acm->data->dev,
"urb %d failed submission with %d\n",
index, res);
} else {
dev_vdbg(&acm->data->dev, "intended failure %d\n", res);
}
set_bit(index, &acm->read_urbs_free);
return res;
Expand Down Expand Up @@ -471,6 +476,7 @@ static void acm_read_bulk_callback(struct urb *urb)
int status = urb->status;
bool stopped = false;
bool stalled = false;
bool cooldown = false;

dev_vdbg(&acm->data->dev, "got urb %d, len %d, status %d\n",
rb->index, urb->actual_length, status);
Expand All @@ -497,6 +503,14 @@ static void acm_read_bulk_callback(struct urb *urb)
__func__, status);
stopped = true;
break;
case -EOVERFLOW:
case -EPROTO:
dev_dbg(&acm->data->dev,
"%s - cooling babbling device\n", __func__);
usb_mark_last_busy(acm->dev);
set_bit(rb->index, &acm->urbs_in_error_delay);
cooldown = true;
break;
default:
dev_dbg(&acm->data->dev,
"%s - nonzero urb status received: %d\n",
Expand All @@ -518,9 +532,11 @@ static void acm_read_bulk_callback(struct urb *urb)
*/
smp_mb__after_atomic();

if (stopped || stalled) {
if (stopped || stalled || cooldown) {
if (stalled)
schedule_work(&acm->work);
else if (cooldown)
schedule_delayed_work(&acm->dwork, HZ / 2);
return;
}

Expand Down Expand Up @@ -567,6 +583,12 @@ static void acm_softint(struct work_struct *work)
}
}

if (test_and_clear_bit(ACM_ERROR_DELAY, &acm->flags)) {
for (i = 0; i < ACM_NR; i++)
if (test_and_clear_bit(i, &acm->urbs_in_error_delay))
acm_submit_read_urb(acm, i, GFP_NOIO);
}

if (test_and_clear_bit(EVENT_TTY_WAKEUP, &acm->flags))
tty_port_tty_wakeup(&acm->port);
}
Expand Down Expand Up @@ -1333,6 +1355,7 @@ static int acm_probe(struct usb_interface *intf,
acm->readsize = readsize;
acm->rx_buflimit = num_rx_buf;
INIT_WORK(&acm->work, acm_softint);
INIT_DELAYED_WORK(&acm->dwork, acm_softint);
init_waitqueue_head(&acm->wioctl);
spin_lock_init(&acm->write_lock);
spin_lock_init(&acm->read_lock);
Expand Down Expand Up @@ -1542,6 +1565,7 @@ static void acm_disconnect(struct usb_interface *intf)

acm_kill_urbs(acm);
cancel_work_sync(&acm->work);
cancel_delayed_work_sync(&acm->dwork);

tty_unregister_device(acm_tty_driver, acm->minor);

Expand Down Expand Up @@ -1584,6 +1608,8 @@ static int acm_suspend(struct usb_interface *intf, pm_message_t message)

acm_kill_urbs(acm);
cancel_work_sync(&acm->work);
cancel_delayed_work_sync(&acm->dwork);
acm->urbs_in_error_delay = 0;

return 0;
}
Expand Down
5 changes: 4 additions & 1 deletion drivers/usb/class/cdc-acm.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -109,8 +109,11 @@ struct acm {
# define EVENT_TTY_WAKEUP 0
# define EVENT_RX_STALL 1
# define ACM_THROTTLED 2
# define ACM_ERROR_DELAY 3
unsigned long urbs_in_error_delay; /* these need to be restarted after a delay */
struct usb_cdc_line_coding line; /* bits, stop, parity */
struct work_struct work; /* work queue entry for line discipline waking up */
struct work_struct work; /* work queue entry for various purposes*/
struct delayed_work dwork; /* for cool downs needed in error recovery */
unsigned int ctrlin; /* input control lines (DCD, DSR, RI, break, overruns) */
unsigned int ctrlout; /* output control lines (DTR, RTS) */
struct async_icount iocount; /* counters for control line changes */
Expand Down

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