From: Nick Piggin <[email protected]>
Date: Wed, 31 Oct 2007 07:42:21 +0100
> Sysrq+T fails to show the stack trace of a running task. Presumably this
> is to avoid a garbled stack, however it can often be useful, and besides
> there is no guarantee that the task won't start running in the middle of
> show_stack(). If there are any correctness issues, then the archietcture
> would have to take further steps to ensure the task is not running.
>
> Signed-off-by: Nick Piggin <[email protected]>
This is useful.
Even more useful would be a show_regs() on the cpu where running tasks
are running. If not a full show_regs() at least a program counter.
That's usually what you're trying to debug and we provide nearly no
way to handle: some task is stuck in a loop in kernel mode and you
need to know exactly where that is.
This is pretty easy to do on sparc64. In fact I can capture remote
cpu registers even when that CPU's interrupts are disabled. I suppose
other arches could do a NMI'ish register capture like this as well.
I have a few bug reports that I can't make more progress on because I
currently can't ask users to do something to fetch the registers on
the seemingly hung processor. This is why I'm harping on this so
much :-)
Anyways, my core suggestion is to add a hook here so platforms can
do the remote register fetch if they want.
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