On Fri, Jul 31, 2020 at 11:47:38PM +0100, Matthew Wilcox wrote:
> On Fri, Jul 31, 2020 at 03:30:16PM -0700, Paul E. McKenney wrote:
> > 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"
> > > <[email protected]> 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.
>
> On non-RT, we could make that lock a raw spinlock. On RT, we could
> decline to take the lock. We'd need to abstract the spin_lock() away
> behind zone_lock(zone), but that should be OK.
>
> But let's see if we need to do that.
Fair enough!
Thanx, Paul
