Reviewing Valentin's patchset made me stare at some memory barriers
on the way. Here is some removal proposal. Some may be beneficial on
runtime (fqs snapshot with potentially as many smp_mb() as the number
of online CPUs for each GP). Some happen on more rare path. In any
case they clarify code reviews so we don't stumble upon mysterious
barriers.

Thanks.

Frederic Weisbecker (6):
  rcu: Remove full ordering on second EQS snapshot
  rcu: Remove superfluous full memory barrier upon first EQS snapshot
  rcu/exp: Remove superfluous full memory barrier upon first EQS
    snapshot
  rcu: Remove full memory barrier on boot time eqs sanity check
  rcu: Remove full memory barrier on RCU stall printout
  rcu/exp: Remove redundant full memory barrier at the end of GP

 .../Tree-RCU-Memory-Ordering.rst              |  6 +++---
 kernel/rcu/tree.c                             | 21 +++++++------------
 kernel/rcu/tree_exp.h                         | 16 +++++++++++---
 kernel/rcu/tree_stall.h                       |  4 ++--
 4 files changed, 26 insertions(+), 21 deletions(-)

-- 
2.44.0

On 15/05/24 14:53, Frederic Weisbecker wrote:
> Reviewing Valentin's patchset made me stare at some memory barriers
> on the way.

Sorry not sorry? :-)

> Here is some removal proposal. Some may be beneficial on
> runtime (fqs snapshot with potentially as many smp_mb() as the number
> of online CPUs for each GP). Some happen on more rare path. In any
> case they clarify code reviews so we don't stumble upon mysterious
> barriers.
>
> Thanks.
>
> Frederic Weisbecker (6):
>   rcu: Remove full ordering on second EQS snapshot
>   rcu: Remove superfluous full memory barrier upon first EQS snapshot
>   rcu/exp: Remove superfluous full memory barrier upon first EQS
>     snapshot
>   rcu: Remove full memory barrier on boot time eqs sanity check
>   rcu: Remove full memory barrier on RCU stall printout
>   rcu/exp: Remove redundant full memory barrier at the end of GP
>
>  .../Tree-RCU-Memory-Ordering.rst              |  6 +++---
>  kernel/rcu/tree.c                             | 21 +++++++------------
>  kernel/rcu/tree_exp.h                         | 16 +++++++++++---
>  kernel/rcu/tree_stall.h                       |  4 ++--
>  4 files changed, 26 insertions(+), 21 deletions(-)
>
> --
> 2.44.0

Le Wed, May 15, 2024 at 07:32:30PM +0200, Valentin Schneider a écrit :
> On 15/05/24 14:53, Frederic Weisbecker wrote:
> > Reviewing Valentin's patchset made me stare at some memory barriers
> > on the way.
> 
> Sorry not sorry? :-)

;-))