(added linux-kernel to CC, since I think it's more of a general kernel
issue)
To be brutally frank, I always thought this disable_irq() mess was a
hack both ugly and fragile. This disable_irq() work that appeared in a
couple net drivers was correct at the time, so I didn't feel I had the
justification to reject it, but it still gave me a bad feeling.
I think the scenario you outline is an illustration of the approach's
fragility: disable_irq() is a heavy hammer that originated with INTx,
and it relies on a chip-specific disable method (kernel/irq/manage.c)
that practically guarantees behavior will vary across MSI/INTx/etc.
Practices like forcedeth's unique locking work for a time, but it should
be a warning sign any time you stray from the normal spin_lock_irqsave()
method of synchronization.
Based on your report, it is certainly possible that there is a problem
with MSI's desc->chip->disable() method... but I would actually
recommend working around the problem by making the forcedeth locking
more standardized by removing all those disable_irq() hacks.
Using spinlocks like other net drivers (note: avoid NETIF_F_LLTX
drivers) has a high probability of both fixing your current problem, and
giving forcedeth a more stable foundation for the long term. In my
humble opinion :)
Jeff
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