hi all,
The transmit functions of ethernet drivers (dev->hard_start_xmit) are
protected to prevent multiple execution of transmits going in parallel. The
general scheme used by most of driver is :
1. Reset NETIF_F_LLTX flag in dev->features and then use kernel locking given
through HARD_TX_LOCK (net/core/dev.c:3417)
OR
2. Use a internal lock of driver generally kept in adapter to prevent multiple
accesses.
In ixgb driver (drivers/net/ixgb/), there is a lock in adapter of driver
(adapter->tx_lock). But this is left before the ixgb_xmit_frame() function
returns. The access to adapter->tx_ring.next_to_use which i suppose will be
the index of next element to use from tx_ring is accessed outside the area
where lock is held. What will prevent race condition during accessing
adapter->tx_ring.next_to_use ?
How does multiple instances of xmit not run or multiple instances of xmit
running is fine ?
Regards,
Mithlesh Thukral
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