[PATCH v6 1/7] can: kvaser_usb: Do not sleep in atomic context

["Ahmed S. Darwish" <darwish.07@gmail.com>]

From: Ahmed S. Darwish <ahmed.darwish@valeo.com>

Upon receiving a hardware event with the BUS_RESET flag set,
the driver kills all of its anchored URBs and resets all of
its transmit URB contexts.

Unfortunately it does so under the context of URB completion
handler `kvaser_usb_read_bulk_callback()', which is often
called in an atomic context.

While the device is flooded with many received error packets,
usb_kill_urb() typically sleeps/reschedules till the transfer
request of each killed URB in question completes, leading to
the sleep in atomic bug. [3]

In v2 submission of the original driver patch [1], it was
stated that the URBs kill and tx contexts reset was needed
since we don't receive any tx acknowledgments later and thus
such resources will be locked down forever. Fortunately this
is no longer needed since an earlier bugfix in this patch
series is now applied: all tx URB contexts are reset upon CAN
channel close. [2]

Moreover, a BUS_RESET is now treated _exactly_ like a BUS_OFF
event, which is the recommended handling method advised by
the device manufacturer.

[1] http://article.gmane.org/gmane.linux.network/239442
    http://www.webcitation.org/6Vr2yagAQ

[2] can: kvaser_usb: Reset all URB tx contexts upon channel close
    889b77f7fd2bcc922493d73a4c51d8a851505815

[3] Stacktrace:

 <IRQ>  [<ffffffff8158de87>] dump_stack+0x45/0x57
 [<ffffffff8158b60c>] __schedule_bug+0x41/0x4f
 [<ffffffff815904b1>] __schedule+0x5f1/0x700
 [<ffffffff8159360a>] ? _raw_spin_unlock_irqrestore+0xa/0x10
 [<ffffffff81590684>] schedule+0x24/0x70
 [<ffffffff8147d0a5>] usb_kill_urb+0x65/0xa0
 [<ffffffff81077970>] ? prepare_to_wait_event+0x110/0x110
 [<ffffffff8147d7d8>] usb_kill_anchored_urbs+0x48/0x80
 [<ffffffffa01f4028>] kvaser_usb_unlink_tx_urbs+0x18/0x50 [kvaser_usb]
 [<ffffffffa01f45d0>] kvaser_usb_rx_error+0xc0/0x400 [kvaser_usb]
 [<ffffffff8108b14a>] ? vprintk_default+0x1a/0x20
 [<ffffffffa01f5241>] kvaser_usb_read_bulk_callback+0x4c1/0x5f0 [kvaser_usb]
 [<ffffffff8147a73e>] __usb_hcd_giveback_urb+0x5e/0xc0
 [<ffffffff8147a8a1>] usb_hcd_giveback_urb+0x41/0x110
 [<ffffffffa0008748>] finish_urb+0x98/0x180 [ohci_hcd]
 [<ffffffff810cd1a7>] ? acct_account_cputime+0x17/0x20
 [<ffffffff81069f65>] ? local_clock+0x15/0x30
 [<ffffffffa000a36b>] ohci_work+0x1fb/0x5a0 [ohci_hcd]
 [<ffffffff814fbb31>] ? process_backlog+0xb1/0x130
 [<ffffffffa000cd5b>] ohci_irq+0xeb/0x270 [ohci_hcd]
 [<ffffffff81479fc1>] usb_hcd_irq+0x21/0x30
 [<ffffffff8108bfd3>] handle_irq_event_percpu+0x43/0x120
 [<ffffffff8108c0ed>] handle_irq_event+0x3d/0x60
 [<ffffffff8108ec84>] handle_fasteoi_irq+0x74/0x110
 [<ffffffff81004dfd>] handle_irq+0x1d/0x30
 [<ffffffff81004727>] do_IRQ+0x57/0x100
 [<ffffffff8159482a>] common_interrupt+0x6a/0x6a

Signed-off-by: Ahmed S. Darwish <ahmed.darwish@valeo.com>
---
 drivers/net/can/usb/kvaser_usb.c |    7 +------
 1 files changed, 1 insertions(+), 6 deletions(-)

diff --git a/drivers/net/can/usb/kvaser_usb.c b/drivers/net/can/usb/kvaser_usb.c
index c32cd61..978a25e 100644
--- a/drivers/net/can/usb/kvaser_usb.c
+++ b/drivers/net/can/usb/kvaser_usb.c
@@ -662,11 +662,6 @@ static void kvaser_usb_rx_error(const struct kvaser_usb *dev,
 	priv = dev->nets[channel];
 	stats = &priv->netdev->stats;
 
-	if (status & M16C_STATE_BUS_RESET) {
-		kvaser_usb_unlink_tx_urbs(priv);
-		return;
-	}
-
 	skb = alloc_can_err_skb(priv->netdev, &cf);
 	if (!skb) {
 		stats->rx_dropped++;
@@ -677,7 +672,7 @@ static void kvaser_usb_rx_error(const struct kvaser_usb *dev,
 
 	netdev_dbg(priv->netdev, "Error status: 0x%02x\n", status);
 
-	if (status & M16C_STATE_BUS_OFF) {
+	if (status & (M16C_STATE_BUS_OFF | M16C_STATE_BUS_RESET)) {
 		cf->can_id |= CAN_ERR_BUSOFF;
 
 		priv->can.can_stats.bus_off++;
-- 
1.7.7.6