Since I'm at least partially to blame for creation of this mailing list (I asked
Andrew Morton for one at the CELF Conference), I thought I might as well stir
things up by throwing a few features out there that I think would improve the
Linux kernel for use in the embedded world:
Crash Diagnostics
-----------------
The single biggest thing we've encountered is the requirement for good diagnostic
reports. We have a fat data pipe to our settop box, but the return pipe is way
too small for kernel core dumps. As a result, we send failure reports that
consist of register and stack dumps for the kernel and current application,
backtraces, etc. Even though some of the details are processor specific, there
are changes we've made in the generic kernel to support doing this. These will be
filtered out gradually as I get time to get them into shape to be submitted.
Continuous Logging for Watchdog Timer Expiration
------------------------------------------------
We run with a watchdog timer that can reboot the system. When we reboot, we lose
all of our status, making it very difficult to determine what went wrong.
Fortunately, there is only one major cause of not refreshing the watchdog--a
driver disabled interrupts for so long that the timer function that resets the
watchdog timer never had a chance to run. So, a way to log what functions were
enable and disabling interrupts on a continuous basis, along with a memory
section that wouldn't be overwritten on reboot, would allow capturing the cause
for these otherwise "silent" reboots.
NVM Filesystems (Separate Metadata?)
------------------------------------
NVM is generally too small to allow for the overhead of filesystem metadata, but
being able to access and manage that data without regard for particular
allocation would be very useful. The good thing is that the data allocation in
NVM is generally static, so data is overwritten but doesn't change size or
location. It would be nice to have some facility to have the metadata be
separately compiled and then to use the normal open/read/write/close interfaces
to use the data. We presently manage allocations with a C header file, but this
is awkward and error-prone.
On-line Disk Partitioning
-------------------------
Server and desktop systems partition their disks at installation time, but some
applications require that partitioning be done after we are already using a root
filesystem on disk. We only have one disk and the driver specifically prevents
changing the partitioning while a disk partition is in use. Note that we don't
want to change the root partition, just other partitions. This drives the need
for some sort of on-line partitioning that allows changing partitions that aren't
in use.
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