Linux Ethernet Bridging - Oct 2013 - [Bridge] [PATCH v3 tip/core/rcu 0/14] Sparse-related updates for 3.13

On Sat, Oct 12, 2013 at 10:13:45AM -0700, Paul E. McKenney
wrote:
> On Fri, Oct 11, 2013 at 11:53:27PM -0700, Josh Triplett wrote:
> > On Fri, Oct 11, 2013 at 04:16:59PM -0700, Paul E. McKenney wrote:
> > > Changes from v2:
> > > 
> > > o	Switch from rcu_assign_pointer() to ACCESS_ONCE() given that
> > > 	the pointers are all --rcu and already visible to readers,
> > > 	as suggested by Eric Dumazet and Josh Triplett.
> > 
> > Hang on a moment.  Do *none* of these cases need write memory
barriers?
> 
> Sigh.  Some afternoons it doesn't pay to touch the keyboard.
> 
> Thank you for catching this.  I will fix, but at this point, I am thinking
> in terms of 3.14 rather than 3.13 for this series.
Some of them looked safe. You could also replace --rcu with __rcu in the
comments while at it.

Thanks,

  Hannes

On Sat, Oct 12, 2013 at 07:39:30PM +0200, Hannes Frederic Sowa
wrote:
> On Sat, Oct 12, 2013 at 10:13:45AM -0700, Paul E. McKenney wrote:
> > On Fri, Oct 11, 2013 at 11:53:27PM -0700, Josh Triplett wrote:
> > > On Fri, Oct 11, 2013 at 04:16:59PM -0700, Paul E. McKenney wrote:
> > > > Changes from v2:
> > > > 
> > > > o	Switch from rcu_assign_pointer() to ACCESS_ONCE() given
that
> > > > 	the pointers are all --rcu and already visible to readers,
> > > > 	as suggested by Eric Dumazet and Josh Triplett.
> > > 
> > > Hang on a moment.  Do *none* of these cases need write memory
barriers?
> > 
> > Sigh.  Some afternoons it doesn't pay to touch the keyboard.
> > 
> > Thank you for catching this.  I will fix, but at this point, I am
thinking
> > in terms of 3.14 rather than 3.13 for this series.
> 
> Some of them looked safe. You could also replace --rcu with __rcu in the
> comments while at it.
Most of them deal with management, maybe a rtnl_assign_pointer with lockdep
check for rtnl lock could help to not clean up the wrong bits.

I don't know if rtnl_assign_pointer is that a could name as it does not
really
explain why the barrier is not needed there. :/

Greetings,

  Hannes

On Sat, Oct 12, 2013 at 07:39:30PM +0200, Hannes Frederic Sowa
wrote:
> On Sat, Oct 12, 2013 at 10:13:45AM -0700, Paul E. McKenney wrote:
> > On Fri, Oct 11, 2013 at 11:53:27PM -0700, Josh Triplett wrote:
> > > On Fri, Oct 11, 2013 at 04:16:59PM -0700, Paul E. McKenney wrote:
> > > > Changes from v2:
> > > > 
> > > > o	Switch from rcu_assign_pointer() to ACCESS_ONCE() given
that
> > > > 	the pointers are all --rcu and already visible to readers,
> > > > 	as suggested by Eric Dumazet and Josh Triplett.
> > > 
> > > Hang on a moment.  Do *none* of these cases need write memory
barriers?
> > 
> > Sigh.  Some afternoons it doesn't pay to touch the keyboard.
> > 
> > Thank you for catching this.  I will fix, but at this point, I am
thinking
> > in terms of 3.14 rather than 3.13 for this series.
> 
> Some of them looked safe. You could also replace --rcu with __rcu in the
> comments while at it.
Sigh!  Will do, thank you!

							Thanx, Paul