Re: [PATCH tip/core/rcu 4/5] sys_membarrier: Add expedited option

[Mathieu Desnoyers]

----- On Jul 25, 2017, at 5:55 PM, Peter Zijlstra peterz@xxxxxxxxxxxxx wrote:

> On Tue, Jul 25, 2017 at 02:19:26PM -0700, Paul E. McKenney wrote:
>> On Tue, Jul 25, 2017 at 10:24:51PM +0200, Peter Zijlstra wrote:
>> > On Tue, Jul 25, 2017 at 12:36:12PM -0700, Paul E. McKenney wrote:
>> > 
>> > > There are a lot of variations, to be sure.  For whatever it is worth,
>> > > the original patch that started this uses mprotect():
>> > > 
>> > > https://github.com/msullivan/userspace-rcu/commit/04656b468d418efbc5d934ab07954eb8395a7ab0
>> > 
>> > FWIW that will not work on s390 (and maybe others), they don't in fact
>> > require IPIs for remote TLB invalidation.
>> 
>> Nor will it for ARM.  Nor (I think) for PowerPC.  But that is in fact
>> what people are doing right now in real life.  Hence my renewed interest
>> in sys_membarrier().
> 
> People always do crazy stuff, but what surprised me is that such s patch
> got merged in urcu even though its known broken for a number of
> architectures.

As maintainer of liburcu, I can certainly say that this patch never made it into
liburcu master branch (official repo at git://git.liburcu.org/userspace-rcu.git).
Paul is referring to a liburcu fork by a github user "msullivan", not the official
tree.

Thanks,

Mathieu


-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com