Re: question about do_IRQ + 4k stacks

[Brian Gerst <bgerst@didntduck.org>]

Terence Ripperda wrote:
> I'm investigating some 4k stack issues with our driver, and I noticed
> this ordering in do_IRQ:
> 
> asmlinkage unsigned int do_IRQ(struct pt_regs regs)
> {
> 	...
> 
> #ifdef CONFIG_DEBUG_STACKOVERFLOW
>         /* Debugging check for stack overflow: is there less than 1KB free? */
>         {
> 	...
>         }
> #endif
> 
> 	...
> 
> #ifdef CONFIG_4KSTACKS
> 
>         for (;;) {
> 	... switch to interrupt stack
>         }
> #endif
> 
> 
> Is the intention of this stack overflow check to catch a currently
> running kernel thread that's getting low on stack space, or is the
> intent to make sure there's enough stack space to handle the incoming
> interrupt? if the later, wouldn't you want to potentially switch to
> your interrupt stack to be more accurate? (I recognize that often you
> will have switched to an empty stack, unless you have nested
> interrupts)
> 

It checks for both process context (system call or kernel thread) or 
interrupt context (nested irqs) stack overflows.

--
				Brian Gerst