infinite spin in RT when booting with DHCP on

[Hector Palacios <hector.palacios@digi.com>]

Hello,

I'm working on a 2.6.31.14 kernel on ARM where I applied the RT PREEMPT patch 
2.6.31.12-rt21.

When booting my platform with DHCP on, the DHCP request is sent by the network driver 
before the PHY has even started the autonegotiation.
Since the PHY is not ready, the TX interrupt returns with NETDEV_TX_BUSY but the 
softirq [sirq-net-tx] seems to have entered an infinite spin, as my system is 
practically hung and 'top' reveals [sirq-net-tx/0] is consuming 95% of CPU. This is 
preventing the PHY autonegotiation (which is scheduled as a delayed work) to start, so 
the PHY is never ready and the packet never reaches the network.

I was wondering if this situation resembles what the patch by Ingo Molnar "tasklet/rt: 
Prevent tasklets from going into infinite spin in RT" describes.

This patch is already in 2.6.31.12-rt21 patch which I'm using so either it is a 
different problem or a corner case of the same issue.

Could anyone tell whether it is the same or a different problem?
Thank you
-- 
Héctor Palacios

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