Re: [RFT] sched_ext: Skip stack trace capture in NMI context

[Joel Fernandes]

> On Dec 24, 2025, at 9:17 AM, Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
> 
> On Tue, 23 Dec 2025 18:58:33 -0500
> Joel Fernandes <joelagnelf@xxxxxxxxxx> wrote:
> 
>> Some documentation suggests IST is required for reliable NMI stack tracing
>> [1] [2] which 32-bit does not have.
>> ”If an interrupt or other exception is taken while the stack or other unwind
>> state is in an inconsistent state, it may not be possible to reliably unwind,
>> and it may not be possible to identify whether such unwinding will be
>> reliable. See below for examples.“
>> 
>> Probably the issue happens to be more of printing garbage than crashing the
>> kernel, but I am not convinced it is stable. Hmm.
> 
> Correct. It's about reliable stack traces, as live kernel patching requires
> that the stack it looks at is reliable before it can modify the code. What
> happens if it's not reliable, means it will just stop at the interrupt
> handler and you don't get to see the rest (or you'll see a bunch of
> functions with "?" in front of them).

Ah, thanks Steve for clarifying!

 - Joel


> 
> -- Steve