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SubjectRe: doublefault debugging (was Re: Linux v2.5.62 --- spontaneous reboots)

On Thu, 20 Feb 2003, William Lee Irwin III wrote:
>
> You might want to grab aeb's fully non-recursive pathwalking if
> you really want to cut back the stack to 4KB, as well as fixing
> whatever stackblasting drivers are about.

The path walking should really not be an issue. Each level of a symlink
takes something like 64 bytes of stack on x86 (I checked it some time ago,
maybe it's changed a bit), since the actual recursive part is very shallow
indeed.

And since we don't recurse deeper than 5 levels anyway, the symlink
recursion ends up not being a real problem compared to a lot of other
code (never mind the single functions with hundreds of bytes of stack
space: just regular function calls 5 levels deep is quite normal).

That fs recursion was not the problem even back in the days when the max
stack depth was <3kB (4kB allocation, 1kB task_struct). It used to be 8
levels deep or something, it was changed to 5 not because we ran out on
x86, but because of those stupid sparc register windows (causing much
bigger minimum function stack requirements than on x86).

Linus

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