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

[Steven Rostedt]

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).

-- Steve