Messages in this thread | | | Date | Thu, 8 Dec 2016 00:15:34 +0100 | From | Francois Romieu <> | Subject | Re: [PATCH 1/2] net: ethernet: sxgbe: remove private tx queue lock |
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Lino Sanfilippo <LinoSanfilippo@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
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