Re: [PATCH 2/3] srcu: queue work without holding the lock

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

On Thu, Sep 28, 2017 at 06:03:57PM +0200, Sebastian Andrzej Siewior wrote:
> On 2017-09-22 11:46:10 [-0700], Paul E. McKenney wrote:
> > On Fri, Sep 22, 2017 at 05:28:05PM +0200, Sebastian Andrzej Siewior wrote:
> > > On RT we can't invoke queue_delayed_work() within an atomic section
> > > (which is provided by raw_spin_lock_irqsave()).
> > > srcu_reschedule() invokes queue_delayed_work() outside of the
> > > raw_spin_lock_irq_rcu_node() section so this should be fine here, too.
> > > If the remaining callers of call_srcu() aren't atomic
> > > (spin_lock_irqsave() is fine) then this should work on RT, too.
> > 
> > Just to make sure I understand...   The problem is not the _irqsave,
> > but rather the raw_?
> 
> exactly. The _irqsave is translated into a sleeping lock on RT and does
> not matter. The raw_ ones stay as they are and queue_delayed_work() uses
> sleeping locks itself and this is where things fall apart.

OK, internally I could get rid of raw_ at the expense of some code bloat,
but in the call_srcu() case, the caller might well hold a raw_ lock.

Thoughts?

							Thanx, Paul