Hi folks-
For a while, I have been trying to work out a method for observing
suspend and resume failures. This has effectively been like pulling
the monitor cable and storage devices, and trying to figure out what
is happening up to a power failure. Up to this point, we have been
using DEBUG printf's to the serial port as it will work till the power
goes out, and is easy to reprogram on restart. However, this limits
usage to debug kernels, and doesn't adapt very well to other possible
devices.
This morning I had the thought that maybe some or all of this
functionality could be handled by having a 'logger' provider in
dtrace. My needs are to have a lightweight non-volatile logging
mechansim that will continue to function while normal hardware I/O
channels are being stopped or powered off. But I considered that this
"feature" might be usefull to other consumers.
The thought here is that this provider would have mechanisms for
alternate places where dtrace data can be sent. In the case of s/r,
the script could set the logger to be an onboard serial port, and
dtrace output would go there (allowing me or other s/r users to
actually use dtrace for debugging - including on production kernels).
However, other loggers, such as USB, storage, or even network could be
defined to suit a users needs.
This is currently little more than just an idea without much thought
as to how it might be implemented. However, I am interested in what
the DTrace community thinks, including if there already is a mechanism
that might do the same (remember, s/r needs are that this continues to
work when most kernel services are off, and needs to be easily started
from power-on). If this is a compelling feature, I would be happy to
give it more thought (as well as solicitation on how to actually
implement it).
Cheers!
---- Randy
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