Re: [tip:tracing/urgent] tracing: Fix too large stack usage indo_one_initcall()

[Ingo Molnar]

* Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:

> On Fri, 21 Aug 2009, Andrew Morton wrote:
> > 
> > We seem to have overrun an 8k stack in
> > http://bugzilla.kernel.org/show_bug.cgi?id=14029

Note that's a 32-bit 8K stack oops, so it doesnt apply.

> The thread "v2.6.31-rc6: BUG: unable to handle kernel NULL pointer 
> dereference at 0000000000000008" also has at least one oops that 
> has that "Thread overran stack, or stack corrupted" marker thing.

This is a 64-bit one, a pty related one and it's not yet clear what 
happened there - but it's certainly possible to overrun any stack.

> > My main concern would be maintenance.  Over time we'll chew more 
> > and more stack space and eventually we'll get into trouble 
> > again.  What means do we have for holding the line at 8k, and 
> > even improving things?
> 
> That's why I think the async thing could fix this - if we _force_ 
> async calls to be asynchronous, you won't have the deep callchains 
> for all the device discovery thing.

Agreed. OTOH we have deep callchains in things like execve() too 
which seem to be a lot harder to fix - and those have been around 
for the past ~10 years since i've been looking at max-stacktraces.
I think 4K doesnt cut it anymore.

	Ingo
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