kern/118093: firewire bus reset hogs CPU, causing data to be lost

[Warner Losh]

> I found the source of this problem.  When a firewire bus resets,
> the firewire driver prints a few lines to the console,
> using printf(9) and device_printf(9).  I suspect that these are
> running at splfw aka splimp, locking out other i/o.

This can't be the case.  There's no SPL involved at all.  Maybe
removing the printfs causes an interrupt to be serviced faster,
resulting in what appears to be better performance...

> Commenting out the *printf() calls fixes the problem, but that
> isn't a good solution.
> 
> Would changing the *printf() calls to log(9) calls be safe?
> ("safe" meaning other i/o doesn't get locked out)
> 
> Ah, for the good old days when 19200 baud seemed fast...
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