Re: Raw spinlocks and memory allocation

[Paul E. McKenney]

On Fri, Jul 31, 2020 at 02:29:19PM -0700, Andrew Morton wrote:
> On Fri, 31 Jul 2020 14:24:57 -0700 "Paul E. McKenney" <paulmck@xxxxxxxxxx> wrote:
> 
> > The reason for this restriction is that in -rt, the spin_lock(&zone->lock)
> > in rmqueue_bulk() can sleep.
> 
> So if there is runtime overhead, this overhead could be restricted to
> -rt kernels with suitable ifdefs?

In theory, yes.  In practice, with CONFIG_PROVE_RAW_LOCK_NESTING=y,
lockdep will complain regardless of -rt or not.

							Thanx, Paul