Re: [RFC][PATCH] 4KB stack + irq stack for x86

Andreas Dilger
2002-10-02T21:56:49Z

On Oct 02, 2002 14:18 -0700, Dave Hansen wrote:
> I've resynced Ben's patch against 2.5.40. However, I'm getting some
> strange failures. The patch is good enough to pass LTP, but
> consistently freezes when I run tcpdump on it.
>
> Although I don't have CONFIG_PREEMPT on, I have the feeling that I
> need to disable preemption in common_interrupt() like it was before.
> Any insights would be appreciated.

I'm a little bit worried about this patch. Have you tried something
like NFS-over-ext3-over-LVM-over-MD or so, which can have a deep stack?

We hit a bunch of deep stack problems like this (overflowing an 8kB stack)
even without interrupts involved when developing Lustre. Granted, we
fixed some large stack allocations in the ext3 indexed-directory code
and in our own code, but I'm still worried that a 4kB stack is too small.

The Stanford checker folks would probably be able to run a test for
large stack allocations in 2.5.40 if you asked them nicely, and maybe
even do stack depths for call chains.

Alternately, you could set up an 8kB stack + IRQ stack and "red-zone"
the high page of the current 8kB stack and see if it is ever used.

Cheers, Andreas
--
Andreas Dilger