Messages in this thread | | | Date | Tue, 20 Dec 2005 16:00:34 +0100 | From | Adrian Bunk <> | Subject | Re: About 4k kernel stack size.... |
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On Tue, Dec 20, 2005 at 09:37:28AM -0500, Mike Snitzer wrote: > On 12/20/05, Adrian Bunk <bunk@stusta.de> wrote: > > On Mon, Dec 19, 2005 at 09:52:53PM -0500, Mark Lord wrote: > > >... > > > The mainline code paths are undoubtedly fine with 4K stacks. > > > It's the *error paths* that are most likely to go deeper on the stack, > > > and those are rarely exercised by anyone. And those are the paths > > > that we *really* need to be reliable. > > > > "most likely" is a strong sentence, especially considering that the > > automatic analysis of all possible call chains can and has already > > identified several such problems (which have now been fixed many months > > ago). > > > > We might not getting 100% security against stack overflows, but that's > > not fundamentally different from the current situation with 6 kB stacks. > > Given this last statement, why is it that Matt Mackall's suggestion in > the "Light-weight dynamically extended stacks" thread didn't get any > _real_ discussion from the big 4K stack advocates? For all intents > and purposes, Matt was dismissed with the same Bunk: "Ever since > neilb's patch there are 0 bugs.. blah blah". 4K, 8K (aka "6 kB") > aside; having more stack safety in the Linux kernel is a "good thing" > no? Aren't dynamic stacks a viable means to imposing 4K (but doing so > with real safety)?
Besides the fact that I still don't think it's requred, Matt's suggestion would work only randomly for functions using more than 1 kB stack.
But discussing hypothetical patches is silly - code talks.
If someone sends a patch implementing Mark's suggestion and it gets measured that this patch doesn't impose a performance penalty we'd have a basis for a real discussion.
> Mike
cu Adrian
--
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