Lino Sanfilippo <linosanfili...@gmx.de> :
> The driver uses a private lock for synchronization between the xmit
> function and the xmit completion handler, but since the NETIF_F_LLTX flag
> is not set, the xmit function is also called with the xmit_lock held.
>
> On the other hand the xmit completion handler first takes the private lock
> and (in case that the tx queue has been stopped) the xmit_lock, leading
> to a reverse locking order and the potential danger of a deadlock.
netif_tx_stop_queue is used by:
1. xmit function before releasing lock and returning.
2. sxgbe_restart_tx_queue()
<- sxgbe_tx_interrupt
<- sxgbe_reset_all_tx_queues()
<- sxgbe_tx_timeout()
Given xmit won't be called again until tx queue is enabled, it's not clear
how a deadlock could happen due to #1.
Regardless of deadlocks anywhere else, #2 has some serious problem due to
the lack of exclusion between the tx queue restart handler and the xmit
handler.
--
Ueimor
