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" <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. > > 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
