Re: [PATCH 11/11 v2.2] ftrace: Add recording of functions that caused recursion

[Steven Rostedt]

On Tue, 3 Nov 2020 15:10:43 +0100
Petr Mladek <pmla...@suse.com> wrote:

> BTW: What is actually the purpose of paranoid_test, please?
> 
> It prevents nested ftrace_record_recursion() calls on the same CPU
> (recursion, nesting from IRQ, NMI context).
> 
> Parallel calls from different CPUs are still possible:
> 
> CPU0                                  CPU1
> if (!atomic_read(&paranoid_test))     if (!atomic_read(&paranoid_test))
>    // passes                            // passes
>    atomic_inc(&paranoid_test);            atomic_inc(&paranoid_test);
> 
> 
> I do not see how a nested call could cause crash while a parallel
> one would be OK.
> 

Yeah, I should make that per cpu, but was lazy. ;-)

It was added at the end.

I'll update that to a per cpu, and local inc operations.

-- Steve