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SubjectRe: Calling current() from interrupt context
On Mon, Oct 09, 2000 at 12:30:17AM +0200, Jamie Lokier wrote:
> Kenn Humborg wrote:
> > My feeling is that interrupt code has no business calling current(),
> > but I don't know the kernel well enough to be sure. Is there any
> > interrupt-level code that calls current() or is it a design
> > principle that it cannot be called?
>
> It's a design principle that you must not call "current" in interrupt,
> bottom half or tasklet context. From time to time buggy code is found
> to do this, and it gets away with it. (See recent thread on network I/O
> signal delivery using the wrong credentials due to a bug like this).
>
> So if you can make the machine crash utterly when calling "current" in
> irq context, or when dereferencing the result, that would probably be a
> good thing :-)

2.4 TCP code relies on current being valid in a softirq.

The m68k port which has a interrupt stack solves the problem by
loading current into a global register variable on all kernel entries.
x86-64 will likely do the same.



-Andi
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