Re: [PATCH 1/4] pch_gbe: Fix transmit queue management

[David Miller]

From: Ondrej Puzman <puzman@xxxxxxxxx>
Date: Thu, 28 Nov 2013 10:44:39 +0100

> According to Documentation/networking/driver.txt the ndo_start_xmit method should not return NETDEV_TX_BUSY under normal circumstances.
> Stop the transmit queue when tx_ring is full.

Please format your commit message text to 80 columns.

> 
> Signed-off-by: Ondrej Puzman <puzman@xxxxxxxxx>

You should be instead preventing the transmit method from being invoked
when it might be possible that a request cannot be satisfied.

This means that at the end of a transmit request, you must stop the
queue if a packet with the maximum number of possible descriptors
cannot be satisfied.  Then it is impossible for the transmit function
to be invoked in a situation where it would need to fail for lack of
available transmit descriptors.

This is why drivers decided whether to stop their TX queues based upon
calculations involving MAX_SKB_FRAGS.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/