Jeff,
I need help with a networking problem and I hope you can direct me to a guru.
As part of the changes in the bcm43xx driver just prior to 2.6.18, some sections
that are executed periodically were made preemptible to reduce latency. For the
most part, the effort was successful; however there are intermittent failures on
certain systems. The code in question is run once per minute, with failures only
after 6-10 hours when they occur. Fortunately for testing purposes, my system is
one that is affected by this problem. In addition, I could tweak the code to run
the problem section once per second. This way, I could experiment with the code
and I think I found the problem.
In the code setting up the preemptive work, the relevant section has the
following:
...
mutex_lock
netif_stop_queue
synchronize_net
....
With this structure, a netdev watchdog tx timeout will happen every few hundred
passes through the code, even if the timeout is set to 30 sec. From
experimentation, I know that if the synchronize_net call is removed, or if it
comes before the netif_stop_queue, I no longer get the errors. Of course it is
possible that my changes just reduce the error rate to a level that I don't see
it with limited testing. I'm hoping that an expert can explain which of these
two changes might be correct, or what should be done.
Thanks,
Larry
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