Jan Kiszka wrote:
Jan Kiszka wrote:
Hi,
this is the preliminary, though already usable result of my recent
effort to extend the tool situation for Xenomai: A kgdb patch series for
2.6.15 on x86. It already works quite well but likely does not yet catch
all fatal scenarios (e.g. page faults in the Xenomai domain).
And here comes another revision (prepare patch remains unmodified).
It gets closer to what Philippe also just suggested in the original
thread: hook KGDB into I-pipe in favour of registering a dedicated
domain. The latter approach modifies the I-pipe state in a way which may
blur the picture of I-pipe itself to the debugger. This revision hooks
exception events into the I-pipe core so that they are delivered the
normal way when the root domain is active, but get catched early for
higher domains like Xenomai. I'm just not sure about the best way to
handle the serial line IRQ. Philippe, do you see problems with current
approach? Should we better hook into __ipipe_handle_irq (which would
make things more complicated, I'm afraid)?
The current approach works fine unless a runaway thread goes wild with
interrupts disabled (i.e. stall bit set) in the root stage or in any
higher priority domain regardless of the root domain state, in which
case the serial IRQ won't make it through the pipeline to KGDB.
In contrast to the first version, exceptions happening in the Xenomai
domain now also get reported to KGDB. Debugging mostly works fine, I'm
just facing unknown problems with intercepting and then continuing
kernel-only RT threads. KGDB sometimes reports "E22" back in this case,
but always locks up. Maybe it gets confused by the fact the there is no
Linux task behind Xenomai kernel threads? I tested this by putting a
breakpoint into xnpod_suspend_thread and running latency in mode 0 and
1. 0 works fine, 1 not.
KGDB is relying on "current", so it's reading garbage over Xenomai's
kernel threads.
--
Philippe.
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