Re: BUG: ib_mad ftrace event unsupported migration

[Jason Gunthorpe]

On Wed, Nov 02, 2022 at 07:44:57AM -0400, Steven Rostedt wrote:
> > before starting throwing some patch into the the air  I would like to align with you the approach we should take here. 
> > 
> > my suggestion here : 
> > - ftrace infra should verify no migration happen  (end and start happens on same CPU)  in case not we will  throw warning for the issue  .
> 
> The scheduler should have. On entering the ring buffer code
> ring_buffer_lock_reserver() it disables preemption and does not
> re-enable it until ring_buffer_unlock_commit().
> 
> The only way to migrate is if you re-enable preemption. WHICH IS A
> BUG!

So what on earth did that?

I'm guessing some driver's query_pkey op, but AFAIK we don't have any
explicit pre-emption reenablements in the code - unless it is sneaky..

Leonid what driver are you testing?

Jason