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Date: Thu, 20 Feb 2003 12:51:13 -0800 (PST)
From: Linus Torvalds <torvalds@transmeta.com>
To: William Lee Irwin III <wli@holomorphy.com>
cc: "Martin J. Bligh" <mbligh@aracnet.com>,
       Alan Cox <alan@lxorguk.ukuu.org.uk>, Ingo Molnar <mingo@elte.hu>,
       Dave Hansen <haveblue@us.ibm.com>,
       Zwane Mwaikambo <zwane@holomorphy.com>, Chris Wedgwood <cw@f00f.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: doublefault debugging (was Re: Linux v2.5.62 --- spontaneous
 reboots)
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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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