Re: [BUG] -next lockdep invalid wait context

["Paul E. McKenney" <paulmck@kernel.org>]

On Thu, Oct 31, 2024 at 08:55:09AM +0100, Sebastian Andrzej Siewior wrote:
> On 2024-10-31 08:35:45 [+0100], Vlastimil Babka wrote:
> > On 10/31/24 08:21, Sebastian Andrzej Siewior wrote:
> > > On 2024-10-30 16:10:58 [-0700], Paul E. McKenney wrote:
> > >> 
> > >> So I need to avoid calling kfree() within an smp_call_function() handler?
> > > 
> > > Yes. No kmalloc()/ kfree() in IRQ context.
> > 
> > However, isn't this the case that the rule is actually about hardirq context
> > on RT, and most of these operations that are in IRQ context on !RT become
> > the threaded interrupt context on RT, so they are actually fine? Or is smp
> > call callback a hardirq context on RT and thus it really can't do those
> > operations?
> 
> interrupt handlers as of request_irq() are forced-threaded on RT so you
> can do kmalloc()/ kfree() there. smp_call_function.*() on the other hand
> are not threaded and invoked directly within the IRQ context.

OK, thank you all for the explanation!  I will fix using Boqun's
suggestion of irq work, but avoiding the issue Boqun raises by invoking
the irq-work handler from the smp_call_function() handler.

It will be a few days before I get to this, so if there is a better way,
please do not keep it a secret!

							Thanx, Paul